File content as of revision 1:b446f401a861:

#include "mbed.h"

AnalogIn rx(p20);

Serial pc(USBTX, USBRX); // tx, rx

int buf[20];
int idx = 0;
int nzeros = 0;

int onCount, offCount;

char decodechar(int start){
    int val = 0;
    for(int i=7;i>=0;i--){
        val += ((int)buf[start+i]) << (7-i);
    }
    return (char) val;
}

int main()
{
    pc.printf("3 CM Link Board - Recieve\n");
    bool calib = true;
    if(calib){
        while(true){
            pc.printf("%f\r\n", rx.read());
            wait_ms(100);
            if(pc.readable()) break;
        }
    }
    idx = 0;
    onCount = 0;
    offCount = 0;
    while(true){
        float v = rx.read();
        if(v > 0.001){
            //pc.printf("1 ");
            onCount++;
            offCount = 0;
        }else{
            if(onCount >= 5 && onCount <= 15){
                buf[idx] = false;
                idx++;
            }else if(onCount >= 15 && onCount <= 25){
                buf[idx] = true;
                idx++;
            }
            onCount = 0;
            offCount++;
            if(offCount >= 25 || idx >=8){
                int c = decodechar(0);
                pc.printf("%c",c);
                for(int i=0;i<8;i++) buf[i] = 0;
                idx = 0;
                offCount = 0;
            }
        }
        
        wait_ms(1);
    }
}