//Displaying ATD channel 0 (POT) on LEDs of PORTT and Tera Terminal (or Hyper Terminal) via SCI0 for HCS12G128 Tower Board 
//Modified and tested by Mazidi from Examples in Chaps 10 and 13 of HCS12 book by Mazidi & Causey 

//On TWR-S12G128 Serial COM0 (SCI0) is IDC 2x5 male header located next to brown POT. 
//The TWR-S12G128 board comes with a DB9-to-IDC-2x5 femal cable for connecting it to the COM port of x86 PC
//When connecting female IDC 2x5 to Tower,make sure pin 1 on IDC Tower board is lined up with the red stripe of the IDC-2x5 cable 
//If the IDC-2x5 cable is connected right, then RED stripe will be on side of USB power cable

//If your x86 PC does not have Serial COM port (with DB-9 connector)then you need USB to Serial Converter
//The best one we have seen is (TRENDnet USB to RS-232 Serial Converter TU-S9) from Amazon
//http://www.amazon.com/TRENDnet-RS-232-Serial-Converter-TU-S9/dp/B0007T27H8/ref=pd_bxgy_e_img_y  



//With Contribution from Shu-Jen Chen
//Notice the on-chip ADC of HCS12G128 is slightly different from the HCS12DT256/512 covered in the textbook
//See Chapter 12/13 (ADC10B12CV2) in the MC9S12GRMV1.pdf ref. Manual



//In TWR-S12G128 the Bus Freq=6.25 MHz. 
//ATD channel 0 (AN0) is connected to RV1 brown Pot Trimer
//Change the POT to see the changes on LEDs of PORTT
//Also bring up the Tera Terminal and see ADC values of 00-0xFF are displayed as ASCII chars  

//In Codewarrior, make sure you are in Open Source BDM
//In Codewarrior F7(make), F5(Debug) and F5 again to start running

#include <hidef.h>      /* common defines and macros */
#include "derivative.h"      /* derivative-specific definitions */

void SerTx0(unsigned char);
void MSDelay(unsigned int);

void main(void) 
{
	unsigned  char x;

	PER0AD = 0x80;		// enable PU on PAD15 to enable COM for the HCS12G128 chip
						// Notiice this is different from HCS12DP256/512
	SCI0BDH=0x00;     
	SCI0BDL=41;     	//12.5 MHz/2=6.25MHz, 6.25MHz/16=390,625 Hz and 390,625/9600=41 
	SCI0CR1=0x00;
	SCI0CR2=0x0C;

	DDRT = 0xF0;		// PORTT as output

	ATDCTL1 = 0;		// 8-bit resolution
	ATDCTL3 = 0x88;		// right justified, one sample per sequence
	ATDCTL4 = 0x02;		// prescaler = 2; ATD clock = 6.25MHz / (2 * (2 + 1)) == 1.04MHz
						// should be between 0.25MHz and 8 MHz per specs.
	for(;;)
	{
		ATDCTL5 = 0;		// start a single conversion on channel 0
				
		while(!(ATDSTAT0 & 0x80));
		  
		x = ATDDR0L;		// read conversion result
		PTT = ~x;			// dump it on LEDs (invert the value because LEDs are low active)
		SerTx0(x);			// send it to SCI0
		SerTx0(' ');

		//MSDelay(1);     //optional
	}
 }

void MSDelay(unsigned int itime)
{
	unsigned int i; unsigned int j;
	for(i=0;i<itime;i++)
		for(j=0;j<1000;j++);
}

 
void SerTx0(unsigned char c)  //SCI0 (COM0 of HCS12 chip)
{
	while((SCI0SR1 & 0x80)==0);  //make sure the last bit is gone
	SCI0DRL=c;		       //before giving it another byte	
}