Category: MOSFETs

I’m considering building an electric scooter; considering it probably putting it lightly.. I have almost everything I need for it.  Interested? Why type so much when you can just watch my proof of concept!

If you’re following along and want to use the same hardware (warning totally untested… ):
Controller found on the TAUTC Tindie Store
Search on eBay for “24VDC scooter motor” ..
..and pick up a MOSFET that’ll pull off a couple 20 amps and saturates at or below 5VDC.
…what am I talking about? Try google or read this.

To the important stuff, the code:

/* 
 * File:   main.c
 * Author: Charles M Douvier
 * Contact at: http://iradan.com
 *
 * Created on March 27, 2014, 4:12 PM
 *
 * Target Device:
 * 18F26K22 on TAUTIC Dev Board
 *
 * Project:
 * Electric Scooter
 *.. a real hack job, comment, delete garbage, etc.
 *
 * Version:
 * 0.1
 *
 */
#ifndef _XTAL_FREQ
#define _XTAL_FREQ 4000000 //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=INTIO67, WDTEN=OFF, PWRTEN=OFF, CP0=OFF, CP1=OFF, BOREN=ON
#pragma config STVREN=ON, LVP=OFF, HFOFST=OFF, IESO=OFF, FCMEN=OFF

//WRT=OFF, FOSC=INTOSC, MCLRE=ON

#define _XTAL_FREQ 4000000 //defined for delay

//clean up on isle 2.. 

    int     an9_value;          //value for a/d
    char    buf[10];            //buff for iota
    long int    fvar;           //long for format math
    long int    tens;           //left of decm
    long int    decm;           //decimal places
    int     tempi;              //to add leadign zeros..
    int     vtxdata;             //volts int for TX
    int     itxdata;

    volatile unsigned int uart_data;    // use 'volatile' qualifer as this is changed in ISR
/*
 * 
 */
void interrupt ISR() {

    if (PIR1bits.RCIF)          // see if interrupt caused by incoming data
    {
        uart_data = RCREG;     // read the incoming data
        PIR1bits.RCIF = 0;      // clear interrupt flag
    }

}

void init_io(void) {
    TRISAbits.TRISA0 = 0; // output
    TRISAbits.TRISA1 = 0; // output
    TRISAbits.TRISA2 = 0; // output
    TRISAbits.TRISA3 = 0; // output
    TRISAbits.TRISA4 = 0; // output
    TRISAbits.TRISA5 = 0; // output
    TRISAbits.TRISA6 = 0; // output
    TRISAbits.TRISA7 = 0; // output

    ANSELA = 0x00; // all port A pins are digital I/O

    TRISBbits.TRISB3 = 1; // AN9
    TRISBbits.TRISB4 = 0; // RB4 = nc
    TRISBbits.TRISB5 = 1; // RB5 = nc
    TRISBbits.TRISB6 = 0; // RB6 = nc
    TRISBbits.TRISB7 = 0; // RB7 = nc

    ANSELB = 0b00001000;     //RB3, AN9

    TRISCbits.TRISC0 = 0; // output
    TRISCbits.TRISC1 = 0; // output
    TRISCbits.TRISC2 = 0; // output
    TRISCbits.TRISC3 = 0; // output
    TRISCbits.TRISC4 = 0; // output
    TRISCbits.TRISC5 = 0; // output
    TRISCbits.TRISC6 = 1; // input
    TRISCbits.TRISC7 = 1; // input
    ANSELC = 0x00; // all port C pins are digital I/O
}

void pwm_init(){

//         PSTR1CONbits.STR1A
//hackhackhackhack... TODO

//    CCPR1L = 0x120;
    CCPR1Lbits.CCPR1L = 0xFE;
    PR2 = 0xFE;
    CCPTMRS0bits.C1TSEL = 0;     //CCP TMR2 Selection
    CCP1CONbits.P1M = 0x00;
    CCP1CONbits.DC1B = 0x00;
    PWM1CONbits.P1RSEN = 0;
    T2CONbits.T2CKPS = 1;  //1:2 Prescale
    T2CONbits.TMR2ON = 1;  //timer 2 go

    CCP1CON = 0x0C;       //PWM (CCP)1 ON

}

void uart_xmit(unsigned int mydata_byte) {

    while(!TXSTA1bits.TRMT);    // make sure buffer full bit is high before transmitting
    TXREG = mydata_byte;       // transmit data
}

void serial_init(void)
{
    //9600 8N1
    // 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)

    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=25;  // here is calculated value of SPBRGH and SPBRGL
    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_ms(50);        // give time for voltage levels on board to settle

    uart_xmit('R');         // transmit some data "restart" notification
}

int main(void) {

    init_io();
    serial_init();
    LATCbits.LATC2 = 0;
    pwm_init();

    // set up oscillator control register, using internal OSC at 4MHz.
    OSCCONbits.IRCF = 0x05; //set OSCCON IRCF bits to select OSC frequency 4MHz
    OSCCONbits.SCS = 0x02; //set the SCS bits to select internal oscillator block

    ADCON0 = 0b00100101;                            //select AN9 and enable
    ADCON1 = 0b00000000;                  //speed Vref=AVdd, VssRef=AVss
    ADCON2 = 0b00111011;                //ledft justified, 20RAD, FRC
    __delay_us(5);

//loop

    while (1) {

        PORTAbits.RA0 = 1; //blinky i'm alive.
        __delay_ms(140);
        PORTAbits.RA0 = 0;
        __delay_ms(140);

            GO = 1;
    while (GO) continue;              //wait for conversion
    an9_value = ADRESH;               //AN9 value

        fvar = an9_value; //this is hacked off another project but works
        fvar = fvar * 10749;        //calibration
        fvar = fvar / 256;
        tens = fvar / 100;
        //tens = tens % 10;
        decm = fvar % 100;
        vtxdata = fvar / 43; //because I'm lazy... I'll change this later.
        uart_xmit(vtxdata);
        CCPR1Lbits.CCPR1L = vtxdata;

    }
    return (EXIT_SUCCESS);
}