// mbed C++ sketch for the ChipDesign SDR antenna
//
// The ChipDesign SDR antenna can be connected to 5 V Arduino shield compatible
// mbed micro-controller boards, such as the Seeeduino Arch (Pro) and the u-blox C027.
// The SDR antenna can be powered and interfaced over USB using any programming language 
// supported by the mbed platform. The varactors are connected to the low-pass filtered 
// PWM ouput pins 3, 5, and 6 of the Arduino platform. Using the PwmOut interface, the
// reverse bias voltage of the varactors can be set between 0 V and 5 V. 
//
// 3.3 V mbed micro-controller boards will require 3.3 V to 5 V level shifters to be 
// inserted to bias the varactors up to 5 V and cover the entire tunable frequency range
// of the SDR antenna.
//
// The firmware code is provided as is.

#include "mbed.h"              

#define FREQ_CMD_LENGTH 5
#define CMD_LENGTH      8

Serial pc(USBTX, USBRX);

PwmOut varactorLeft(p24); 
PwmOut varactorTop(p25);
PwmOut varactorRight(p26);

static void runFreqCommand(char* freqCommand);

int main() 
{    
    int i = 0;
    char command[] = "!!!!!!!!!!";

    while(1) 
    {
        int c = pc.getc();
        pc.putc(c);
        
        if (i < CMD_LENGTH && c != 0xD)
            command[i++] = (char) c;
        else
        {
            if (i>=FREQ_CMD_LENGTH && strncmp(command,"FREQ:",FREQ_CMD_LENGTH) == 0)
            {
                pc.printf("Freq Command Received %x\n",strcmp(command,"freq"));
                runFreqCommand(command+FREQ_CMD_LENGTH);
            }
            else
                pc.printf("Unknown command\n");

            i = 0;
            memset(command,0,sizeof(char)*CMD_LENGTH);
            pc.printf(">> ");
        }
        
            
    }
}

static void runFreqCommand(char* freqCommand)
{
    char *strPtr;
    int freq = strtol(freqCommand,&strPtr,10);
    pc.printf("Frequency Parsed: %d\n",freq);
    
    switch (freq)
    {
        case 700:
        varactorLeft = 0.1;
        varactorTop = 0.1;
        varactorRight = 0.1;
        break;
        
        default:
        pc.printf("Unknown frequency\n",freq);

    }
        
}