/*
 * File:   main.c
 * Author: oncley
 *
 * This for use to get the Crista IMU data into TRAM without losing characters.
 * Extremely simple baud rate down-scaler:
 * input stream at 115200 baud, output stream at 19200 baud
 *
 * Created on November 18, 2011, 11:04 PM
 * Various edits through Dec, 2011.
 * Fixed April 28, 2011 [had been removing 0 values in que_out! now using outflag]
 *
 * Dec 27, 2013: removed serial data checking that seems to throw out too much.
 */

#include <p24F32KA301.h>
#define XTAL_FREQ 8MHZ
#define CLRWDT() {__asm__ volatile ("clrwdt");}
#define DI() {__asm__ volatile ("disi #16383");} // I <think> this disables all interrupts

/* internal FRC clock, clock output enabled, fail-safe disabled */
_FOSCSEL(FNOSC_FRC);
_FOSC(OSCIOFNC_ON & FCKSM_CSDCMD);

/* WDT enabled with long timeouts */
_FWDT(WDTPS_PS32768 & FWPSA_PR128 & FWDTEN_ON & WINDIS_OFF);

#define QTOP 999
#define QBOT 0
#define QLEN 1000

char buf[QLEN];
int rfpop, rfpush, outflag;

char que_out() {
    char c;
    if (rfpush != rfpop) {
        outflag = 1;
        c = buf[rfpop];
        if (rfpop == QTOP)
            rfpop = QBOT;
        else
            rfpop++;
    } else {
        outflag = 0;
        c = 0;
    }
    return c;
}

void que_in(char qdata) {
    buf[rfpush] = qdata;
    if (rfpush == QTOP)
        rfpush = QBOT;
    else
        rfpush++;
}

int main(void) {
    char c;
    int rstat;

    /* Pins used:
     *  U1Tx - pin11; RB7; CN23
     *  U1Rx - pin6; RB2; SDA2; AN4; CTED13, CN6
     *  U2Tx - pin4; RB0; SDI2; AN2; CN4
     *  U2Rx - pin5; RB1; AN3; CTED12; CN5
     */
    DI();  // disable all interrupts (forever!)

    /* initialize variables */
    rfpush = QBOT;
    rfpop = QBOT;
    outflag = 0;

    /* initialize ports */
    ANSA = 0x0000; // turn off portA A/Ds
    ANSB = 0x0000; // turn off portB A/Ds
    SPI1STAT = 0x0000; // SPI1 disabled
    SPI2STAT = 0x0000; // SPI2 disabled
    I2C1CON = 0x0000; // I2C1 disabled
    I2C2CON = 0x0000; // I2C2 disabled
    CTMUCON1 = 0x0000; // CTMU disabled
    CNEN1 = 0x0000; // Change Notification bits disabled
    CNEN2 = 0x0000; // Change Notification bits disabled
    TRISA = 0xFFFF; // all portA bits are input
    TRISB = 0x3F7E; // all portB bits are input except the 2 Tx pins (0,7) and debug (15)

    OSCTUN = 0x0020; // lower oscillator to improve baud rate match [WORKS!!!]

    /* UART1 to 115200 baud */
    U1BRG = 1; // 8.5% high
    U1MODE = 0x8800; // Enabled, 8-N-1, no hardware flow control
    U1STA =  0x0400; // Enable transmit [not yet used]

    /* UART2 to 19200 baud */
    U2BRG = 12; // 0.2% high
    U2MODE = 0x8800; // Enabled, 8-N-1, no hardware flow control
    U2STA = 0x0400; // Enable transmit

    /* Continuous loop */
    while (1) {

    /* Poll input UART for byte; put into queue if available */
        rstat = U1STA;
        if ((rstat & 0x0001)==0x0001) {
//            if ((rstat & 0x000E)==0x0000) { // only save if no read errors [ignore errors for now]
                c = (char)(U1RXREG & 0x00FF);
                que_in(c);
//            }
//            else U1STA = 0x0400; // clear error flag
        }

   /* Poll output UART; if empty, write byte from queue */
        if ((U2STA & 0x0100)==0x0100) {
            c = que_out();
            if (outflag==1) U2TXREG = (int)c;
        }
        CLRWDT();
    }
    return 0; // never gets here
}