Combining serial stream bytes/nibbles to make a number.

I thought I’d drop this here for someone who needed a copy-paste solution.

I am parsing a serial string output from a YDLIDAR X4 rotating lidar. I have to do this because the library sucks. a lot. I mean I’m not over my heels with the unit anyhow, first off who the hell outputs at 128,000 baud? I’ll post the code when it’s done enough for someone to build off of it.

I was getting an error in number of bytes in the packet as parsed from the serial string so I had to break out the function into really busy but obvious code to see where I was going wrong. The code has me concatenating two bytes and an upper nibble. Ignore the discrepancy in how I added my bytes backwards in my code vs. how the device actually stacks it’s data… because you know: WHO IN THEIR RIGHT MIND SHIFTS LSB ON THE LEFT?! (note the “length bytes as shown in 12 bits and the “response length” example below.)

Anyhow… feel free to show me how to do it better in the comments. Obviously this is built for you to look at it do it’s magic in a serial monitor.

//Arduino Friendly.
unsigned long rx_make_length(byte b1, byte b2, byte b3) {
  unsigned int msb_bits = 0; 
  unsigned long length_value = 0;
  
  //drop the lower nibble and prep for OR-ing.
  b3 = b3 >> 4;

  Serial.print("c w/ nibble removed and right shift: "); Serial.println(b3, HEX);

  msb_bits = b1;   
  msb_bits = msb_bits << 8;
  Serial.print("b1 shifted up 8 : "); Serial.println(msb_bits, HEX);
  msb_bits = msb_bits | b2;
  Serial.print("b1 concatenated w/ b2: "); Serial.println(msb_bits, HEX);
  length_value = msb_bits;
  length_value = length_value << 4; 
  Serial.print("b1 concatenated w/ b2 w/ shift: "); Serial.println(length_value, HEX);
  length_value = length_value | b3;
  Serial.print("b1 concatenated b2 and b3: "); Serial.println(length_value, HEX);

  return length_value;
}

//unsigned long my_value = rx_make_lenth(a, b, c);

iButtonLink / DS18B20 Arduino Datalogger

What a groaner.. who needs another datalogger? Well I do, so stuff it. I was inspired to check out these iButtonLink devices that allow you to daisy-chain connect a number of devices in a single circuit of sorts with RJ45 patch cables. I had seen these a couple years ago in some top-notch datacenters that terminated to a concentrator (4 strings) that were then pushed up to some IBM services app server.

A while back I published a Microsoft PIC microcontroller version of this … I decided to give it another whirl with the “easy button” … Arduino. Of course there were a couple libraries that I just had to collectively stuff into the same sketch and easy-peasy it was done in an hour or so.

This time I have my data stored to an SD card, which … I hastily put together.

If I was actually going to finish this I would add three things to this to finish it up.

  1. Use an RTC, figure an interface to enter the correct time. (maybe add an ethernet shield and get NTP?) … or just manual enter.
  2. I’d grab the interval time off the RTC and just have the loop do a non-blocking wait, then poll the RTC time or interrupt (whatever you favorite way to do this is..) that way I was collecting trend information on the “:00″s.
  3. I would add a method of checking for an SD card to be interested and allow it to start logging from card insert. I would also add time/date stamp to the file and finally, still SD card related I would check file size and stop logging when I got close to full.

So that is that. I’ve been creating a lot of fun lately but nothing mind-bending.. just going through every module I’ve ever bought doing the demo code … or going the other way around.. working on every Arduino demo/example in a class .. I’ve also built an FE boat, moved my workshop inside (update video coming kind of soon) and been working on PopBot 0.5 ..

The code:

/*
 * Chas Ihler
 * @chasxmd
 * https://iradan.com
 * 
 * License: Public Domain - it's mostly copy and paste and preferences anyways.
 * 
 * iButtonLink, grabs all sensors and logs them to card if present.
 * Recommendations: 
 * Add an RTC and a method of updating time. 
 * I'd also grab actual seconds off the RTC for logging and use a non-blocking wait for the polling/logging. 
 * 
 * Libraries:
 * https://github.com/matmunk/DS18B20
 * IDE built in SD card/SPI library
 * 
 * Sensor: 
 * https://www.ibuttonlink.com/products/t-sense-temperature-sensor
 * which has this device within.. 
 * https://datasheets.maximintegrated.com/en/ds/DS18B20.pdf
 * 
 * Hookup:
 * You'll need a pullup resistor from 5V to pin 2
 * ibutton hookup:
 * 1 - GND
 * 2 - 5VDC
 * 3 - NC
 * 4 - Arduino Pin 2 (w/ Pullup)
 * 5 - GND
 * 6 - NC
 * 7 - NC
 * 8 - NC
 * 
 *  SD card attached to SPI bus as follows:
 * MOSI - pin 11
 * MISO - pin 12
 * CLK - pin 13
 * CS - pin 4 
 * 
 */

#include <DS18B20.h>
#include <SPI.h>
#include <SD.h>


DS18B20 ds(2);    //pin 2

const int chipSelect = 4;

void setup() {
  Serial.begin(115200);
  delay(100);

  Serial.println("----------------------------------------");
  Serial.println(" ");
  Serial.println("DS18B20 / iButtonLink Demo");
  Serial.print("Devices: ");
  Serial.println(ds.getNumberOfDevices());
  Serial.println(" ");
  Serial.println("----------------------------------------");
   Serial.print("Initializing SD card...");

  // see if the card is present and can be initialized:
  if (!SD.begin(chipSelect)) {
    Serial.println("Card failed, or not present");
    // don't do anything more:
    while (1);
  }
  Serial.println("card initialized.");
}

void loop() {
  int i_address;
  Serial.println("----------------------------------------");
  while (ds.selectNext()) {
    String str_dataString = "";
    switch (ds.getFamilyCode()) {
      case MODEL_DS18S20:
        Serial.println("Model: DS18S20/DS1820");
        break;
      case MODEL_DS1822:
        Serial.println("Model: DS1822");
        break;
      case MODEL_DS18B20:
        Serial.println("Model: DS18B20");
        break;
      default:
        Serial.println("Unrecognized Device");
        break;
    }

    uint8_t address[8];
    ds.getAddress(address);
    
    Serial.print("Address:");
    for (uint8_t i = 0; i < 8; i++) {
      Serial.print(" ");
      Serial.print(address[i]);
      str_dataString += String(address[i]);
    }
    Serial.println();
/*
    Serial.print("Resolution: ");
    Serial.println(ds.getResolution());

    Serial.print("Power Mode: ");
    if (ds.getPowerMode()) {
      Serial.println("External");
    } else {
      Serial.println("Parasite");
    }
*/
    Serial.print("Temperature: ");
    Serial.print(ds.getTempC());
    Serial.print(" C / ");
    Serial.print(ds.getTempF());
    Serial.println(" F");
    
    str_dataString += ",";
    str_dataString += String(ds.getTempC()); 
    File dataFile = SD.open("datalog.txt", FILE_WRITE);
    
    if (dataFile) {
        dataFile.println(str_dataString);
        dataFile.close();
        Serial.println(str_dataString);
    }  else {
        Serial.println("error opening datalog.txt");
    }
    Serial.println("        *****       ");
    Serial.println(); 
  }

  delay(30000);
}

Happy Making!

Re-Post: iButtonLink T-Sense 1-wire sensor (Maxim DS18B20) + PIC 18F14K22

Using a PIC Microcontroller to pull temperature of iButtonLink T-sense sensor.

I pulled this off the wayback machine because I lost this post in the great database loss of how ever many years ago. I’m re-posting because I’m working on an expanded version of this with an Arduino dev board and wanted a reminder of what I did five years ago. Originally posted 1/2/2015. No edits.

—————————————————————————————————————-

I came across a stash of iButton T-sense 1-wire sensors.. so I grabbed a couple and decided to check out 1-wire.

Maxim makes a 1-wire device called the DS18B20. It’s a 9-12 bit temperature sensor with the possibility of being powered by parasitic power from the data line. This cuts the signal path down to a single DQ line and a return. A company called iButtonLink produces a nice little wrapper around this device called a T-Sense. There are a couple pieces of software out there that will allow you to hook these up to monitoring systems, I don’t have any though. These devices come with a 64-bit address code and can be daisy-chained which makes having many of these devices monitored very nice.

At first I thought, ugh.. lame I have to send, and parse 64-bit codes in a little 8 bit micro.. doesn’t sound like a ton of fun for just fooling around on a day off.. thank fully they have a “Skip ROM” feature/command which works similar to a broadcast but can only be used when you have one device on the bus. If there is one thing left in this project I might consider finishing it’d be to add the addressing in and daisy-chain a few of these.

Most of my research came from Microchip’s Application Note AN1199 though the T-Sense Users Manual also helped out including determining the wiring diagram.

For my circuit I hooked up 5VDC (but later ran it on 3.3V just fine) and the 5VDC return on pins 1 & 2. Then the DQ link and return on pins 4&5. The signaling is interesting as the 1-wire bus needs a weak pull and works with an open collector circuits. The master starts all signaling, writes and reads. The 1’s and 0’s are based on how long the master or slave sinks the DQ line. To accomplish this in the PIC microcontroller I switched the port from an output to a three state input when I needed the port to be in weak-pull up mode (which is also hand when I need to sample the port for a response from a slave). The pull up on the resistor in my circuit is 10Kohm but I’ve seen 4.7KOhm and I’m sure anywhere in the neighborhood is fine. Finally if you do some digging you’ll notice I run this in low speed mode, if I remember correctly the “high speed” mode is 4x faster. I don’t think speed of data transfer is really relevant when you’re waiting for 750ms for a temperature conversation though.

I initially started with just determining if there was a 1-wire device on the bus. If you perform a “reset” (master sinks the bus low for 480us then releases to hi-z for 70us and then performed a sample.. any (all) device(s) will sink the line slow to prove their presence…then another 410us of delay before continuing. I got this one first try.. better luck than my first time with I2C! I then wrote the code (including sampling tidbits of Microchip AN1199 code to optimize) to do an actual temperature conversion and request it (by commanding a “read scratch pad”). The device dumps all 9 bytes of it’s registers. On that note I just remembered I should mention I did NOTHING with the CRC byte.. that’s all you if you care.

My temperature conversion code looks like this: (bus control m = master or PIC, s=slave or sensor)

m RESET

s PRESENCE flag

m SKIP ROM (0xCC)

m CONV TEMP (0x44)

m HOLD DQ (Hold line high 750ms for 12bit conversion .. I am guessing we hold it high for the parasitic power supply)

m RESET

s PRESENCE flag

m SKIP ROM (0xCC)

m READ SCRATCHPAD (0xBE)

s 9 Bytes of Data

The 12-bit conversion is basically 0.0625 deg C for every bit from 0C, The LSB holds a temperature sign.

The output of my program looks like..

Final Results!

There are tons of details on what a “1” is an what a “0” is, the ROM code (READ ROM, MATCH ROM), changing the configuration to 9bit for 94 ms conversions over 12bit 750ms conversions. This is all stuff you can grab out of the DS18B20 specification sheet or AN1199.

I hope you get some use out of this.. I still have enough of these T-Sense modules.. maybe if someone really wants one I’ll drop it in the mail… or perhaps we can set up a big box of electronics to ship around and I can dump some in there.

Items I used to make this happen:

TAUTIC 20-pin Development Board

Microchip PIC 18F14K22

AST Breadboard Buddy Pro

AST tinyLEDx4

iButtonLink T-Sense

CAT5 breakout board (eBay?)

Microchip PICKit 3

Then miscellaneous tools, test equipment, jumpers and a breadboard.

The good stuff (my code):

.. also found here on pastebin: http://pastebin.com/HrLg1GqL

/*
 * File:   main.c
 * Author: Charles M Douvier
 * Contact at: http://iradan.com
 *
 * Created on Janurary 1, 2015
 *
 * Target Device:
 * 18F14K22 on Tautic 20 pin dev board
 *
 * Project: Maxim 1-Wire Testing
 *
 * Details of 1-wire protocol using Microchip AN1199
 * Field device http://datasheets.maximintegrated.com/en/ds/DS18B20.pdf
 * The 1-Wire Protocol is registered trade mark of Dallas/Maxim semiconductor.
 *
 * Some code was use by the AN1199 App Note Source code; I got stuck looking for a fast way of txing by bit-bang (yes never did this before)
 * The agreement below mentions a license agreement accompaning this software; There was none. I'll note where this software was used if you
 * want to re-write without the Microchip bits.
 * The Microchip licensing as follows:
 *
 *  * FileName:        1wire.c
 * Dependencies:
 * Processor:       PIC18
 * Complier:        MCC18 v3.13
 * Company:         Microchip Technology, Inc.
 *
 * Software License Agreement
 *
 * Copyright © 2004-2007 Microchip Technology Inc.  All rights reserved.
 *
 * Microchip licenses to you the right to use, copy and distribute Software
 * only when embedded on a Microchip microcontroller or digital signal
 * controller and used with a Microchip radio frequency transceiver, which
 * are integrated into your product or third party product (pursuant to the
 * sublicense terms in the accompanying license agreement).  You may NOT
 * modify or create derivative works of the Software.
 *
 *
 * You should refer to the license agreement accompanying this Software for
 * additional information regarding your rights and obligations.
 *
 * SOFTWARE AND DOCUMENTATION ARE PROVIDED “AS IS” WITHOUT WARRANTY OF ANY
 * KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION, ANY WARRANTY
 * OF MERCHANTABILITY, TITLE, NON-INFRINGEMENT AND FITNESS FOR A PARTICULAR
 * PURPOSE. IN NO EVENT SHALL MICROCHIP OR ITS LICENSORS BE LIABLE OR OBLIGATED
 * UNDER CONTRACT, NEGLIGENCE, STRICT LIABILITY, CONTRIBUTION, BREACH OF
 * WARRANTY, OR OTHER LEGAL EQUITABLE THEORY ANY DIRECT OR INDIRECT DAMAGES OR
 * EXPENSES INCLUDING BUT NOT LIMITED TO ANY INCIDENTAL, SPECIAL, INDIRECT,
 * PUNITIVE OR CONSEQUENTIAL DAMAGES, LOST PROFITS OR LOST DATA, COST OF
 * PROCUREMENT OF SUBSTITUTE GOODS, TECHNOLOGY, SERVICES, OR ANY CLAIMS BY
 * THIRD PARTIES (INCLUDING BUT NOT LIMITED TO ANY DEFENSE THEREOF), OR OTHER
 * SIMILAR COSTS.
 *
 *
 *
 * Version:
 * 0.1  Configuration, with reset test
 * 0.2
 *
 */
#ifndef _XTAL_FREQ
#define _XTAL_FREQ 16000000 //4Mhz FRC internal osc
#define __delay_us(x) _delay((unsigned long)((x)*(_XTAL_FREQ/4000000.0)))
#define __delay_ms(x) _delay((unsigned long)((x)*(_XTAL_FREQ/4000.0)))
#endif
#include 
#include 
#include 
#include 
//config bits
#pragma config FOSC=IRC, WDTEN=OFF, PWRTEN=OFF, MCLRE=ON, CP0=OFF, CP1=OFF, BOREN=ON
#pragma config STVREN=ON, LVP=OFF, HFOFST=OFF, IESO=OFF, FCMEN=OFF
#define _XTAL_FREQ 16000000 //defined for delay
/*
 * Variables
 */
    int     device_present;             // 1 = 1-wire device on 1-wire bus
    int     i, x, y, int_temp, an4_value;               //
    long int    decm;
    int     itxdata, txdata;            //int RS232 tx data
    char    rxbuff[10], z[1], buf[4];                 //buffer for T-sense 1-wire device
    float    temperature, f, d;
    volatile unsigned int uart_data;    // use 'volatile' qualifer as this is changed in ISR
/*
 *  Functions
 */
    void interrupt ISR() {
    if (PIR1bits.RCIF)          // see if interrupt caused by incoming data .. unused currently
    {
        uart_data = RCREG;     // read the incoming data
        PIR1bits.RCIF = 0;      // clear interrupt flag
                                //
    }
    // I left this timer interrupt if I needed it later. This is unused.
    if (PIR1bits.TMR1IF)
    {
        //T1CONbits.TMR1ON = 0;
        PIR1bits.TMR1IF = 0;
        //T1CONbits.TMR1ON = 1;
    }
}
     void __delay_10ms(unsigned char n)     //__delay functions built-in can't be used for much at this speed... so!
 {
     while (n-- != 0) {
         __delay_ms(10);
     }
 }
void uart_send (unsigned int mydata_byte) {      //bytes
    while(!TXSTAbits.TRMT);    // make sure buffer full bit is high before transmitting
    TXREG = mydata_byte;       // transmit data
}
void write_uart(const char *txt)                //strings
{
                                //this send a string to the TX buffer
                                //one character at a time
       while(*txt)
       uart_send(*txt++);
}
//This code if from Microchip but is unused currently.
void uart_send_hex_ascii(unsigned char display_data)
{
	//unsigned char temp;
	//temp = ((display_data & 0xF0)>>4);
	//if (temp <= 0x09)
	//	Putchar(temp+'0');
	//else
	//	Putchar(temp+'0'+0x07);
        //
	//temp = display_data & 0x0F;
	//if (temp <= 0x09)
	//	Putchar(temp+'0');
	//else
	//	Putchar(temp+'0'+0x07);
	//Putchar('\r');
	//Putchar('\n');
}
void serial_init(void)
{
    // calculate values of SPBRGL and SPBRGH based on the desired baud rate
    //
    // For 8 bit Async mode with BRGH=0: Desired Baud rate = Fosc/64([SPBRGH:SPBRGL]+1)
    // For 8 bit Async mode with BRGH=1: Desired Baud rate = Fosc/16([SPBRGH:SPBRGL]+1)
    TXSTAbits.BRGH=1;       // select low speed Baud Rate (see baud rate calcs below)
    TXSTAbits.TX9=0;        // select 8 data bits
    TXSTAbits.TXEN=1;     // enable transmit
    BAUDCONbits.BRG16=0;
    RCSTAbits.SPEN=1;       // serial port is enabled
    RCSTAbits.RX9=0;        // select 8 data bits
    RCSTAbits.CREN=1;       // receive enabled
    SPBRG=25;               //38,400bps-ish
                            //BRG16=0, 7=31.25k, 25=9.615k
    PIR1bits.RCIF=0;        // make sure receive interrupt flag is clear
    PIE1bits.RCIE=1;        // enable UART Receive interrupt
         __delay_ms(10);        // give time for voltage levels on board to settle
}
void init_io(void) {
    ANSEL = 0x00;         
    ANSELH = 0x00;
    TRISAbits.TRISA0 = 0; // output
    TRISAbits.TRISA1 = 0; // output
    TRISAbits.TRISA2 = 0; // output
    TRISAbits.TRISA4 = 0; // output
    TRISAbits.TRISA5 = 0; // output
    TRISBbits.TRISB4 = 0; // output
    TRISBbits.TRISB5 = 1; // input (RX UART)
    TRISBbits.TRISB6 = 0; // output
    TRISBbits.TRISB7 = 0; // output (TX UART)
    LATC = 0x00;
    TRISCbits.TRISC0 = 1; // AN4
    TRISCbits.TRISC1 = 1; // 1-wire data
    TRISCbits.TRISC2 = 0; // 
    TRISCbits.TRISC3 = 0; // 
    TRISCbits.TRISC4 = 0; // 
    TRISCbits.TRISC5 = 0; // output
    TRISCbits.TRISC6 = 1; // input
    TRISCbits.TRISC7 = 1; // input
}
void init_adc (void)
{
    ANSELbits.ANSEL4=1;         //PORTC.0
    ADCON2bits.ADCS = 0x02;     //Fosc/32
    ADCON2bits.ADFM=0;          //left oriented
    ADCON1=0x00;
}
void read_adc (void)
{
    ADCON0bits.CHS0 = 0;        // AD4
    ADCON0bits.CHS1 = 0;
    ADCON0bits.CHS2 = 1;
    ADCON0bits.CHS3 = 0;
    ADCON0bits.ADON = 1;        // A/D ON
    __delay_us(5);
    ADCON0bits.GO   = 1;        // ..GO!
    __delay_us(5);
        while (ADCON0bits.GO) continue;              //wait for conversion
        an4_value = ADRESH;                          //AN4 value
}
void one_wire_reset(void) {
    device_present = 0x00;
    TRISCbits.TRISC1 = 0;
    LATCbits.LATC1 = 0;
    __delay_us(240);        //delay 480 us
    __delay_us(240);
    TRISCbits.TRISC1 = 1;
    __delay_us(70);
    if (!PORTCbits.RC1) {
            device_present = 0x01;
    }
    __delay_us(205);        //delay 410 us
    __delay_us(205);
}
//this looks a lot like the Microchip code, it was not I just happened to be on the right track.
void one_wire_tx_bit(unsigned char txbit) {         // write a bit
    if (txbit) {
    TRISCbits.TRISC1 = 0;
    LATCbits.LATC1 = 0;
    __delay_us(6);    
    TRISCbits.TRISC1 = 1;
    __delay_us(64);      
    }
    else {      
    TRISCbits.TRISC1 = 0;
    LATCbits.LATC1 = 0;
    __delay_us(60);    
    TRISCbits.TRISC1 = 1;
    __delay_us(10);    
    }
}
//from Microchip AN1199 code, renamed and slightly modified to match my software
/**********************************************************************
* Function:        void OW_write_byte (unsigned char write_data)
* PreCondition:    None
* Input:		   Send byte to 1-wire slave device
* Output:		   None
* Overview:		   This function used to transmit a complete byte to slave device.
*				   
***********************************************************************/
void one_wire_tx_byte (unsigned char write_data)
{
	unsigned char loop;
	
	for (loop = 0; loop < 8; loop++) 	{ 		one_wire_tx_bit(write_data & 0x01); 	//Sending LS-bit first 		write_data >>= 1;					// shift the data byte for the next bit to send
	}	
}	
//from Microchip AN1199 code: I gathered the essence of this but seeing as I am not using most of the AN1199 code
//and this would not work with XC8 I had to re-write this.
/**********************************************************************
* Function:        unsigned char OW_read_bit (void)
* PreCondition:    None
* Input:		   None
* Output:		   Return the status of the OW PIN
* Overview:		   This function used to read a single bit from the slave device.
*				   
***********************************************************************/
unsigned char one_wire_rx_bit (void)
{
	unsigned char read_data; 
        read_data = 0x00;
	//reading a bit 
	TRISCbits.TRISC1 = 0;
        LATCbits.LATC1 = 0; 						// Drive the bus low
	__delay_us(6);						// delay 6 microsecond (us)
	TRISCbits.TRISC1 = 1;  						// Release the bus
	__delay_us(9);						// delay 9 microsecond (us)
        if (PORTCbits.RC1) {                                    //read 1 or 0
            read_data = 0x01;
        }
	__delay_us(55);						// delay 55 microsecond (us)	
	return read_data;
}
/**********************************************************************
* Function:        unsigned char OW_read_byte (void)
* PreCondition:    None
* Input:		   None
* Output:		   Return the read byte from slave device
* Overview:		   This function used to read a complete byte from the slave device.
*				   
***********************************************************************/
unsigned char one_wire_rx_byte (void)
{
	unsigned char loop, result=0;
	
	for (loop = 0; loop < 8; loop++)                // here we are reading 8 bits (1 byte) 	{ 		 		result >>= 1; 				// shift the result to get it ready for the next bit to receive
		if (one_wire_rx_bit())
		result |= 0x80;				// if result is one, then set MS-bit
	}
	return result;					
}	
void one_wire_conversion_pulse(void) {
    	TRISCbits.TRISC1 = 0;
        LATCbits.LATC1 = 1; 		 //For T conv we drive the DQ line high for 750ms (12bit)
	__delay_us(250);                 // delay 
	__delay_us(250);                  
        __delay_us(250);                  
	TRISCbits.TRISC1 = 1; 
        LATCbits.LATC1 = 0;             //just in case this causes problems elsewhere                              
}
int main(void) {
    init_io();
    // set up oscillator control register, using internal OSC at 16MHz.
    OSCCONbits.IRCF = 0x07; //set OSCCON IRCF bits to select OSC frequency 16MHz
    OSCCONbits.SCS = 0x02; //set the SCS bits to select internal oscillator block
    //RCONbits.IPEN = 0;          //dsiable priority levels
    INTCONbits.PEIE = 1;        // Enable peripheral interrupt
    INTCONbits.GIE = 1;         // enable global interrupt
    init_adc();                 //unused but AN4 is there if I need it
    serial_init();
    uart_send ('x');
        LATAbits.LATA0 = 0; //this is just for debugging with an LA..
        __delay_us(1);
        LATAbits.LATA0 = 1; //also confirms oscillator setup is correct.. 1us width
        __delay_us(1);
        LATAbits.LATA0 = 0;
    while (1) {
        one_wire_reset();
        if (device_present) {
            LATCbits.LATC2 = 1;             //this is a 1-wire device out there for debugging
            one_wire_tx_byte(0xCC);         //skip-rom (similar to a broadcast)
            one_wire_tx_byte(0x44);         //do a temp conversion
            one_wire_conversion_pulse();    // hold DQ line high for 750ms
            one_wire_reset();
            //add additional check here later
            one_wire_tx_byte(0xCC);         //skip-rom (similar to a broadcast)
            one_wire_tx_byte(0xBE);         //read scratch pad
            for(i = 0; i<9; i++)            //reading all 9 bytes on the T-Sense
   		rxbuff[i] = one_wire_rx_byte();
            // T-Sense
            //  Byte 0 LSB of Temp
            //  Byte 1 MSB of Temp and sign
            // LSB
            //  2^3 2^2 2^1 2^0 2^-1 2^-2 2^-3 s^-4
            // MSB
            // S S S S S 2^6 2^5 2 ^ 4
            temperature = 0;
            f = 0.0625;
            //z[0] = rxbuff[1];
            //x = atoi(z);
            x = rxbuff[1];
            if (x & 0b10000000) {
                uart_send('-');
            } else {
                uart_send('+');
            }
            
            x = x & 0b00000111;
            int_temp = 0;
            int_temp = rxbuff[0];
            if (x & 0b00000001)
                int_temp = int_temp + 0x100;
            if (x & 0b00000010)
                int_temp = int_temp + 0x200;
            if (x & 0b00000100)
                int_temp = int_temp + 0x400;
            temperature = int_temp * f;
            
            int_temp = temperature;
            itoa(z, int_temp, 10);
            write_uart(z);
            uart_send('.');
            d = temperature - int_temp;
            decm = d * 1000;
            //page 374 of XC8 user guide
            ltoa(buf,decm,10);  //long conversion to buffer
            y=strlen(buf);  //uh, adding leading zeros..
            y=3-y;      //probably a better way of doing thing
            while (y)       //first figure out how many zeros
            {
                uart_send('0');  //missed 3-string length
                y=y-1;  //then send them until done
            }   
            write_uart (buf);
        
            uart_send(0x0A);        //LF
            uart_send(0x0D);        //CR
            //temperature   float temperature
            //int_temp      interger value of temperature
            __delay_10ms(254);
        }
    }
    return (EXIT_SUCCESS);
}

ESP32 Boot Camp

… for me.

I got a rando e-mail offering me “free parts” and I usually don’t even bother opening the e-mail. It’s ALWAYS garbage right? Well, maybe I hadn’t slept well the night before but I opened it. (psss. You can scroll down about a page before I actually get anywhere in this post…)

What was I thinking? I hovered carefully over the link… seemed pretty safe… short-ish domain ended with a .com .. not extra stuff on the end… OK. They got me. The website was http://digitspace.com — It seemed like an electronics website so I e-mailed. Back…. going back and forth they seem to be running some kind of promotion or perhaps they are trying to build some brand recognition getting bloggers to give them some advertising. In the end selected $50 worth of parts that consisted of two ESP32 micro dev boards that had WiFi (of course), LoRa, OLED display and and extra LED. There was some switch button types but they were a bit more and for some reason I didn’t think I needed them. Well a week later these things actually showed up (and I didn’t have to give them my credit card or paypal info!).

OK THE START..

A week later the boards showed up in the mail.. they look and feel reasonable and they came with some sample firmware that proved they worked. Unfortunately the site did not include any documentation… but I did the “hardwork” for you if you want to follow along… but let’s start with the end… So far I am here:

First thing first I had to add ESP32 support to my Arduino IDE.. I dropped this in the “additional board manager URLs”:

https://dl.espressif.com/dl/package_esp32_index.json

See how in this quick video..

I found a simple tx-rx LoRa code off the internet but I won’t share because it took too much re-work to get working on my board. So I took it’s essience …

I had to add these libraries:

Add libraries:
Adafruit SSD1306 by Adafruit
Adafruit GFX Library by Adafruit
LoRa by Sandeep Mistry

(all came right off the normal library manager)

I couldn’t find an OLED library that worked until reading some and found I liked this one that seemed to be the “best for me”:
https://github.com/osresearch/esp32-ttgo

After that it was smooth sailing. My code is work-in-progress towards my final project. It can be found here: https://github.com/chasihler/TTGO-OLED-RX-TX-HTTP-PUT

Inspiration along the way:

Battery Monitoring: https://github.com/YogoGit/TTGO-LORA32-V1.0

A nice post, read too late, had the correct pinout/board of many different but similar boards: http://brettbeeson.com.au/ttgo-lora-esp32-v2-1-r1-6/

Putting your ESP32 to sleep:
https://randomnerdtutorials.com/esp32-deep-sleep-arduino-ide-wake-up-sources/

My findings were similar … though I haven’t ACCURATELY measured it my USB analyzer says 50mA on and 10mA off.. no peak readings yet but I can live with 10mA in my project.

MODbus/RTU on a PIC Microcontroller

By request one of my long lost blogs was a MODbus RTU application for a PIC 18F27J53. You could easily plop this onto many of the 18F series micros. It doesn’t do much but it’s a great stepping stone for throwing in your own IO. I’ll probably follow up with an Arduino version in a while.. I’ll put it on my “todo” list.

The code…

/*
 File:   main.c
 Author: Charles M Ihler
 Contact at: http://iradan.com
 *
 Created on November 8, 2014, 2:37 PM
 *
 Target Device:
 18F27J53 Development Board by AtomSoft
 *
 Project: MODbus/RTU slave
 *
 Notes
 We will ignore both query high bytes for now
 TODO:   Pull all hard coded IO out eventually and set it up via USB?
 Maybe a terminal application for enabling points?
 *
 *
 Version:
 0.02     Controlled sends caned reply on request to address on RS-232
 0.03     CRC works on RX
 0.04     No actual IO yet..
 Function 0x02 (Read Input Status) Started
 0.05     Ported to 18F17J53 for expanded IO/USB options.
 12MHz XTAL with CPUDIV set to 16MHz
 *
 / //#ifndef _XTAL_FREQ //#define _XTAL_FREQ 16000000 // //#define __delay_us(x) _delay((unsigned long)((x)(_XTAL_FREQ/4000000.0)))
 //#define __delay_ms(x) _delay((unsigned long)((x)*(_XTAL_FREQ/4000.0)))
 //#endif 
 // PIC18F27J53 Configuration Bit Settings
 // 'C' source line config statements
 include 
 // #pragma config statements should precede project file includes.
 // Use project enums instead of #define for ON and OFF.
 // CONFIG1L
 pragma config WDTEN = OFF      // Watchdog Timer (Disabled - Controlled by SWDTEN bit)
 pragma config PLLDIV = 3       // PLL Prescaler Selection (Divide by 3 (12 MHz oscillator input))
 pragma config CFGPLLEN = ON    // PLL Enable Configuration Bit (PLL Enabled)
 pragma config STVREN = ON      // Stack Overflow/Underflow Reset (Enabled)
 pragma config XINST = OFF       // Extended Instruction Set (Enabled)
 // CONFIG1H
 pragma config CPUDIV = OSC3_PLL3// CPU System Clock Postscaler (CPU system clock divide by 3 from 48MHz)
 pragma config CP0 = OFF        // Code Protect (Program memory is not code-protected)
 // CONFIG2L
 pragma config OSC = HSPLL      // Oscillator (HS+PLL, USB-HS+PLL)
 pragma config SOSCSEL = HIGH   // T1OSC/SOSC Power Selection Bits (High Power T1OSC/SOSC circuit selected)
 pragma config CLKOEC = OFF      // EC Clock Out Enable Bit  (CLKO output enabled on the RA6 pin)
 pragma config FCMEN = OFF      // Fail-Safe Clock Monitor (Disabled)
 pragma config IESO = OFF       // Internal External Oscillator Switch Over Mode (Disabled)
 define _XTAL_FREQ 16000000 //defined for delay
 char    ctxt[10], buf1, testcrc[4];    //buff serial string volatile unsigned int     ping, isrcall, index, reading, new_rx; int address, crc_high, crc_low, i, querylength; unsigned int result; //these variables are for fuctions to be enabled/disabled and pushed into application code via later int frame, z, bufferbits, query_reg_address, y; char data_out[64]; char reg_address[255];
 /*
  *
 Interrupt Service
 *
 UART RX and Timer 1
 *
 */
 void interrupt ISR() {
 if (PIR1bits.RCIF)          // see if interrupt caused by incoming data
 {
     isrcall = 0x01;
     char temp;
     temp = RCREG;     // read the incoming data
     buf1 = temp;
     if(temp==address && reading==0)      //if my address..
     {
         index = 0;                  //reset index
         reading = 1;                //from now on go to else if
         LATCbits.LATC1 = 1;
         new_rx = 0;
         ping = 1;
     }
     else if(reading == 1)           //in middle of GPS sentence
     {
         //TODO reset timeout timer
         ctxt[index] = temp;         //load it up
         index++;                    //increment index
         ping = 1;                   //this is for debugging
         if(index > 6)              //1+7 = master frame.
             {
             index = 0;              //reset index
             reading = 0;            //no longer storing the string
             new_rx = 1;             //"ding"
             T1CONbits.TMR1ON = 0;
             }
     }
 }
 //RCSTA2bits.FERR = 0;    //Clear errors
 //RCSTA2bits.OERR = 0;
 //time out timer, if tripped new_rx=0;
 if (PIR1bits.TMR1IF)
 {
     new_rx=0;
     ping = 0;
     T1CONbits.TMR1ON = 0;
     PIR1bits.TMR1IF = 0;
     if (reading) {
     reading = 0;
     LATCbits.LATC0 = 1;
     }
 }
 } 
 void init_io(void) {
 INTCONbits.GIE = 0;         //no interruptions please ADCON0 = 0b00000000;        //don't need any ADC ADCON1 = 0b00000000;        //speed Vref=AVdd, VssRef=AVss LATA = 0x00; LATB = 0x00; LATC = 0x00; TRISAbits.TRISA0 = 1; // address 1 TRISAbits.TRISA1 = 1; // address 2 TRISAbits.TRISA2 = 1; // address 3 TRISAbits.TRISA3 = 0; // output TRISAbits.TRISA5 = 0; // output TRISBbits.TRISB0 = 0; // TRISBbits.TRISB1 = 1; // TRISBbits.TRISB2 = 0; // TRISBbits.TRISB3 = 0; // TRISBbits.TRISB4 = 0; //  TRISBbits.TRISB5 = 1; //  TRISBbits.TRISB6 = 0; //  TRISBbits.TRISB7 = 0; //  TRISCbits.TRISC0 = 0; // timer LED output TRISCbits.TRISC1 = 0; // output TRISCbits.TRISC2 = 0; // LED test output TRISCbits.TRISC3 = 0; // output //TRISCbits.TRISC4 = 1; // USB //TRISCbits.TRISC5 = 1; // USB TRISCbits.TRISC6 = 0; // output TX1 TRISCbits.TRISC7 = 1; // input  RX1
 }
 void __delay_10ms(unsigned char n)     //__delay functions built-in can't be used for much at this speed… so!
  {
      while (n-- != 0) {
          __delay_ms(10);
      }
  }
 void uart_xmit(unsigned int mydata_byte) {
 while(!TXSTAbits.TRMT);    // make sure buffer full bit is high before transmitting TXREG = mydata_byte;       // transmit data
 }
 void write_uart(const char txt) {                                 //this send a string to the TX buffer                                 //one character at a time        while(txt)
        uart_xmit(*txt++);
 }
 void serial_init(void)
 {
     //9600 8N1
 TXSTA1bits.SYNC = 0; TXSTA1bits.BRGH=1;       // select low speed Baud Rate (see baud rate calcs below) TXSTA1bits.TX9=0;        // select 8 data bits TXSTA1bits.TXEN = 1;     // enable transmit RCSTA1bits.SPEN=1;       // serial port is enabled RCSTA1bits.RX9=0;        // select 8 data bits RCSTA1bits.CREN=1;       // receive enabled SPBRG1=102; SPBRGH1=0; PIR1bits.RCIF=0;        // make sure receive interrupt flag is clear PIE1bits.RCIE=1;        // enable UART Receive interrupt INTCONbits.PEIE = 1;    // Enable peripheral interrupt INTCONbits.GIE = 1;     // enable global interrupt  __delay_10ms(5);        // give time for voltage levels on board to settle
 }
 void run_timer (void) {
     T1CONbits.TMR1ON = 0;
     TMR1=0;
     TMR1L=0x00;
     TMR1H=0xAA;
     T1CONbits.TMR1CS = 0x01;
     T1CONbits.T1CKPS = 0x01;
     PIE1bits.TMR1IE = 1;
     T1CONbits.TMR1ON = 1;
 //        PIR1bits.TMR1IF=0;
 }
 void check_my_address(void) {
     /*
      *  Determine what address the unit is based on DIP switches
      *  PORTAbits.RA0   Switch 1
      *  PORTAbits.RA1   Switch 2
     */
 if (PORTAbits.RA0 & PORTAbits.RA1) address = 0x04; if (!PORTAbits.RA0 & PORTAbits.RA1) address = 0x03; if (PORTAbits.RA0 & !PORTAbits.RA1) address = 0x02; if (!PORTAbits.RA0 & !PORTAbits.RA1) address = 0x01;
 }
 /*
 TODO
 Poll the inputs
 *
 I will probably use a 74138 to address banks with 74HC245 for byte/banks of inputs
 I will likely use the same set up for "Coils"
 For input registers (analog inputs) I will consider perhaps some kind of A/D input with CD4066+74HC138
 *
 */ 
 void poll_my_inputs(void) {
 //just stuff it with something for now for (z = 0; z < 64; ++z) { reg_address[z] = z; }
 }
 /*
 did the chicken come before the egg?
 this MODbus CRC bit was gently borrowed from the internet..
 I can't determine who wrote it.. it shows up in an Ardiuno Sketch for MODbus
 Modbus over serial line - RTU Slave Arduino Sketch
 with referenced of Juan Pablo Zometa, Samuel Marco, Andras Tucsni, Philip Costigan
 It also shows up on a number of websites and forums uncredited… many PIC or C based ..
 so who knows, but I didn't write it
 The MODbus CRC-16 function is outlined on the Modicon site for reference
 */
 unsigned int modbus_crc(unsigned char buf[], int start, int cnt)
 {
 int     i,j;
 unsigned temp, temp2, flag;
 temp=0xFFFF;
 for (i=start; i<cnt; i++){
    temp=temp ^ buf[i];
 for (j=1; j<=8; j++){       flag=temp & 0x0001;      temp=temp >> 1;
      if (flag) temp=temp ^ 0xA001;
      }
   }
 /*** Reverse byte order. ***/
 temp2=temp >> 8;
 temp= (temp << 8) | temp2;
 return(temp);
 } 
 int check_master_crc (void) {
 int diff, diff1, diff2;       //what we send back char data[6]; result = 0x0000; crc_high = 0x00; crc_low = 0x00; data[0] = address;  //this is ugly but all master queries are 6bytes+CRC so it'll do data[1] = ctxt[0];  //function data[2] = ctxt[1];  //start_addressH data[3] = ctxt[2];  //start_addressL data[4] = ctxt[3];  //# of regH data[5] = ctxt[4];  //# of regL result = modbus_crc(data,0,6); crc_high = result >> 8; crc_low = result & 0x00FF; diff1 = ctxt[5] ^ crc_high; diff2 = ctxt[6] ^ crc_low; diff = diff1 + diff2; //this spits back an XORed value between calculated and received CRC return(diff);
 }
 void respond_input_status(void) {
         //ctxt[1] start_addressH
         //ctxt[2] start_addressL
         //ctxt[3] # of regH
         //ctxt[4] # of regL
     querylength = ctxt[4];  //ignoring upper byte for now (TODO)
     query_reg_address = ctxt[2]; //ignoring upper address byte (TODO)
 frame = 0;     //data frame counter do {     data_out[frame] = reg_address[query_reg_address];     //TODO  make this do somethng     querylength--;     frame++; } while (querylength>0); querylength = ctxt[4];  //reload so we can count time transmitting data result = modbus_crc(data_out,0,2); crc_high = result >> 8; crc_low = result & 0x00FF; //uart_xmit response address, function, data_out[frames], CRC uart_xmit(address); uart_xmit(ctxt[0]); frame = 0; do {     uart_xmit(data_out[frame]);     //TODO  make this do somethng     querylength--;     frame++; } while (querylength>0); uart_xmit(crc_high); uart_xmit(crc_low);
 }
 int main(void) {
     OSCCONbits.SCS = 0x00;
 new_rx=0; init_io(); serial_init(); run_timer(); check_my_address(); y += address; write_uart("MODBus "); uart_xmit(y); LATCbits.LATC0 = 1; LATCbits.LATC1 = 1; __delay_10ms(50); LATCbits.LATC0 = 0; LATCbits.LATC1 = 0; if (address == 0x01){     LATCbits.LATC0 = 1; } if (address == 0x02) {     LATCbits.LATC1 = 1; } __delay_10ms(50); LATCbits.LATC0 = 0; LATCbits.LATC1 = 0; INTCONbits.GIE = 1; INTCONbits.PEIE = 1; while (1) {     //If read data, not me and then if no 232 traffic for >800us then any xmit over     //104 us (9600) x 8 quiet periods minus some for wiggle.     if (ping) {         run_timer();     }     if (new_rx) {       //this device was polled         //testing response         i = check_master_crc();     //check master query crc         if (i==0x00) {              //CRC Ok?             if (ctxt[0] == 2) {       //coil status query                 respond_input_status();             }             //TODO other types of functions go here         }         //all done, get ready for new query         new_rx = 0;     }     //testcrc[0] = 0xFF;     //testcrc[1] = 0x02;      //right now this is only thing processed     //result = modbus_crc(testcrc,0,2);     //crc_high = result >> 8;     //crc_low = result & 0x00FF;     __delay_10ms(10);     LATCbits.LATC2 = 1; //LED blinky test     __delay_10ms(10);     LATCbits.LATC0 = 0;     LATCbits.LATC1 = 0;     LATCbits.LATC2 = 0; }
 }
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