File content as of revision 1:6e34363efa95:

#include "mbed.h"

#define VERSION "0.0.2"

DigitalOut motor1A(p9);
DigitalOut motor1B(p10);
DigitalOut motor2A(p11);
DigitalOut motor2B(p12);
DigitalOut motor3A(p13);
DigitalOut motor3B(p14);
DigitalOut motor4A(p15);
DigitalOut motor4B(p16);

PwmOut motor1(p21);
PwmOut motor2(p22);
PwmOut motor3(p23);
PwmOut motor4(p24);

DigitalOut digital1(p17);
DigitalOut digital2(p18);
DigitalOut digital3(p19);
DigitalOut digital4(p20);
DigitalOut led(LED1);

SPI spi(p5, p6, p7); // mosi(out), miso(in), sclk(clock)
DigitalOut cs(p8); // cs(select)

Serial pc(USBTX, USBRX);
// for latency calculation and transmission count
Timer timer;
unsigned long a, temp, count;
// for enableing disableing autosending sensor values
bool autosend;
// the analog sensor values for ADC
volatile uint8_t* values;
volatile uint8_t* location;
// the serial message buffer
volatile char command[3];
volatile int index;

// maps the value x to a new given range
double map(double x, double in_min, double in_max, double out_min, double out_max) 
{
    return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}

// shifts 2 8 bit bytes into one integer
int getIntValue( uint8_t high, uint8_t low ) 
{
    return (high << 8) | low;
}

// sets the given pwm value
void setPWM(int value, PwmOut pwm, DigitalOut a, DigitalOut b) 
{
    // block the motors
    if (value > 511) {
        a = 0;
        b = 0;
        pwm = 1;
    } else {
        // clockwise run
        if (value > 255) {
            value = value - 256;
            a = 0;
            b = 1;
        } else {
            a = 1;
            b = 0;
        }
        // map the 0-255 value to 0-1
        pwm = map(value, 0, 255, 0, 1);
    }
}

// specifies the action for the user input
void specifyAction(char action, int value)
{
    // specify the action
    switch (action) {
        case 40:
            // print the version of this software
            pc.printf("%s",VERSION);
            pc.putc(255);
            break;
        case 41:
            // enable or disable autosending sensor values
            autosend = value;
            break;
        case 42:
            // send last command latency
            pc.putc(temp >> 8);
            pc.putc(temp);
            // the end of the message
            pc.putc(255);
        case 44:
            // print the analogs and digitals
            // the sensor reading checksum
            char checksum = 0;
            // restart pointer
            values = location;
            // print analog sensor values
            for(int i = 0; i < 16; i++) {
                pc.putc(*(values));
                // add analog sensor to the checksum                
                checksum ^= *(values++);
            }
            // add digital sensors to the checksum
            checksum ^= '\0';
            // print digital sensor values
            pc.putc('\0');
            // print checksum
            pc.putc(checksum);
            // print last latency value
            pc.putc(temp >> 8);
            pc.putc(temp);
            // send packet count
            count++;
            pc.putc(count >> 16);
            pc.putc(count >> 8);
            pc.putc(count);
            // the end of the message
            pc.putc(255);
            break;
        case 162:
            // set the first PWMs value
            setPWM(value, motor1, motor1A, motor1B);
            break;
        case 163:
            // set the second PWMs value
            setPWM(value, motor2, motor2A, motor2B);
            break;
        case 164:
            // set the third PWMs value
            setPWM(value, motor3, motor3A, motor3B);
            break;
        case 165:
            // set the fourth PWMs value
            setPWM(value, motor4, motor4A, motor4B);
            break;
        case 230:
            // Goto _reset ?
            break;
        case 231:
            // enable or disable servos
            if (value == 1) {
                // enable servo ?
            } else if (value == 2) {
                // disable servo ?
            }
            break;
        case 233:
            // set digitals values
            digital1 = (value & 1);
            digital2 = ((value >> 1) & 1);
            digital3 = ((value >> 2) & 1);
            digital4 = ((value >> 3) & 1);
            break;
        default:
            pc.printf("unspecified command\n");
    }
}

// for reading external ADC values
int readSensor(int channel, DigitalOut select)
{  
    // sending the 5 bits + 2 bits to ignore the null bits
    // coming from the device, so the data that is sent is 11000101
    uint8_t commandbits = 0xC0;
    commandbits |= (channel << 2);
    
    // select the device
    select = 0;
    // send command bits
    spi.write(commandbits);
    // now the device sends back the readings 12 bits, 7 bits at a time
    uint8_t high = spi.write(0x0);
    uint8_t low = spi.write(0x0);
    low = low >> 2;

    // shift to get the high and low byte
    high = (high >> 3);
    low = ( high << 5) | low;

    // deselect the device
    select = 1;

    // save the values
    *(values++) = high;
    *(values++) = low;
    
    return 0;
}

// serial interrupt method
void serialEvent() 
{
    // if we are getting a new message
    if(!index) {
        // mark the time
        a = timer.read_us();
    }
    char c = pc.getc();
    // if we received enter
    if( c == 255 ) {
        specifyAction(command[ 0 ], getIntValue(command[ 1 ], command[ 2 ]));
        index = 0;
        // calculate the latency
        temp = timer.read_us() - a;
    }
    // otherwise add byte to buffer
    else {
        command[index++] = c;
    }
}

// the main method
int main() 
{
    // Setup the spi for 7 bit data, high steady state clock,
    // second edge capture, with a 1MHz clock rate
    spi.format(7,0);
    spi.frequency(1000000);
    
    // specify the usb baud rate
    pc.baud(115200);

    // allocate 16 bytes of space for the adc values
    values = (uint8_t*) malloc(16);
    // remember the first values aadress
    location = values;

    // attach a serial interrupt
    pc.attach(&serialEvent);

    // to indicate programm is running
    led = 1;

    timer.start();
    // endless loop
    while (true) {
        values = location;
        for (int i=0; i<8; i++) {
            readSensor(i, cs);
        }
        if(autosend)
            specifyAction(44,0);
    }
}