Code for S12 sci / UART
This is some code I've found backed up in my email from 2007 for a project I did with a S12. I can't say this was a working copy. Though I think this will demonstrate some of the complexity with getting getting serial communications working.
/* sci.c
*
*
*
* Author: djm and drk
*/
#include <mc9s12c32.h>
#include "globals.h"
#include "sci.h"
#include <stdio.h>
#include <string.h>
/* Gloabals */
#define MIW ('A')
#define SCI_TIMEOUT (15) // 15 * 20 ms = 300 ms
#define debugSCI (1)
char debug[30];
U_BYTE txBuffer[255]; //FIFO Queue
U_BYTE txBufferInIndex =0;
U_BYTE txBufferOutIndex =0;
#pragma CODE_SEG NON_BANKED
interrupt void sci_isr(void)
{
SCIInterruptHandler();
PTT = (PTT&(~0x04)) | ((PTT^0x04)&0x04);
}
#pragma CODE_SEG DEFAULT
void InitSCI(void) /* */
{
SCIBDH = 0x00;
SCIBDL = 0x1A; // SCI0BDL = 0x1A;
SCICR1 = 0x04; /* Mr Vardons Settings ILT*/
SCICR2 = 0x2C; /* Trial and error from Debugger RIE | ILIE | TE */
//Test
clearTxBuffer();
/* Enable LOOPS for Test*/
//SCICR1 |= LOOPS;
}
void clearTxBuffer(void)
{
int i;
for(i =0; i<255; i++)
{
txBuffer = 'A';
}
}
void SCIInterruptHandler(void)
{
U_BYTE dummyData;
/* Clear Flag*/
if (SCISR1 & (RDRF + OR))
{
// clear the interrupt flag by reading the status register and
// then the data register
dummyData = SCISR1;
dummyData = SCIDRL;
//Echo
ProcessSCIByte(dummyData);
}
if ((SCICR2 & SCICR2_TIE) && (SCISR1 & TDRE))
{
TransmittBufferEmpty();
}
}
void TransmittBufferEmpty(void)
{
U_BYTE dummyData;
// clear the interrupt flag by reading the status register
dummyData = SCISR1;
if(txBufferOutIndex < txBufferInIndex)
{
SCIDRL = txBuffer[txBufferOutIndex++]; // Put Byte in SCI Transmitt Register
}
else
{
// turn off the transmit empty interrupt
SCICR2 &= ~SCICR2_TIE;
txBufferInIndex = 0;
txBufferOutIndex = 0;
}
}
void TransmittMessage(char * message)
{
int i;
for(i =0; message != '\0' ; i++)
{
txBuffer[txBufferInIndex++] = message; // Add to Queue
}
if ((SCICR2 & SCICR2_TIE) == 0) // If Transmitt Empty Interrupt Disabled
{
SCIDRL = txBuffer[txBufferOutIndex++]; // Service Byte
SCICR2 |= SCICR2_TIE; // Enable Tx Empty Interrupt
}
}
/*
Method to buffer Recieved Bytes until full message is recieved.
MIW -> DataLength -> Data -> DataChecksum
*/
void ProcessSCIByte(U_BYTE sciData)
{
static U_BYTE state = 0;
static U_BYTE dataLength = 0;
static U_BYTE dataBytesRecieved = 0;
static U_BYTE rxBuffer [36];
static U_BYTE rxBufferIndex = 0;
static U_BYTE dataChecksum =0;
static U_WORD timeout = 0;
/*
Will time out messages, not in debug mode
*/
#if debugSCI
if (state > 0 && timer20msTick > timeout)
{
state = 0;
dataLength = 0;
dataBytesRecieved = 0;
rxBufferIndex = 0;
dataChecksum =0;
}
#endif
switch(state)
{
case 0: //MIW
{
if(sciData == MIW) // Correct MIW
{
state = 1;
timeout = timer20msTick + SCI_TIMEOUT;
#if debugSCI
// Debug Message
sprintf(debug, "Valid MIW Found: %c \n\r", sciData);
TransmittMessage(debug);
#endif
}
else // Incorrect MIW
{
state = 0;
#if debugSCI
// Debug Message
sprintf(debug, "Invalid MIW Found: %c \n\r", sciData);
TransmittMessage(debug);
#endif
}
break;
}
case 1: //Message Length
{
dataLength = sciData-176; //Conversion from ASCII to Numerical, needed for talking to Hyperterminal.
state = 2;
#if debugSCI
// Debug Message
sprintf(debug, "Message Length is: %d \n\r", dataLength);
TransmittMessage(debug);
#endif
break;
}
case 2: // Buffer Data
{
rxBuffer[dataBytesRecieved++] = sciData;
dataChecksum += sciData;
#if debugSCI
// Debug Message
sprintf(debug, "Data is:%c \n\r", sciData);
TransmittMessage(debug);
#endif
if (dataBytesRecieved == dataLength)
{
state = 3;
#if debugSCI
// Debug Message
sprintf(debug, "Data Complete!!!!\n\r");
TransmittMessage(debug);
#endif
}
break;
}
case 3: // Checksum
{
if (sciData == dataChecksum) //valid message
{
#if debugSCI
// Debug Message
sprintf(debug, "Checksum Correct!!!! : %d \n\r", dataChecksum);
TransmittMessage(debug);
#endif
}
else
{
#if debugSCI
// Debug Message
sprintf(debug, "Checksum Failed!!!! : %d \n\r", dataChecksum);
TransmittMessage(debug);
#endif
}
//Test
state = 4; // No Break on Purpose
}
case 4: //Clear Variables
{
state = 0;
dataLength = 0;
dataBytesRecieved = 0;
rxBufferIndex = 0;
dataChecksum =0;
break;
}
}
}
