Using the TTL port

[Astronouth7303]

I can tell you more about hardware than software.

The Program port is a standard DCE RS-232 port.

To my knowledge, TTL uses an almost identical format as RS-232, the difference is that it uses different voltages. The wave forms are identical, though.
RS-232 is 1 = -3v to -25v; 0 = 3v to 25v.
TTL is (generally) 1 = 5v; 0 = 0v.

My favorite site on this is Beyond Logic, and Thier serial article.

In the RCs, the Prog port is USART1 in api, the TTL is USART2.

In the MCC18 Libraries Doc (C:\mcc18\doc\MPLAB-C18-Libraries.pdf), the API info can be found in section 2.10 (p. 58). There is probably more info on Microchip's web site, but that's down at the moment.

[Gene F]

Astronouth7303,
Here is the code we used to talk to a second micro that was keeping track of our position. It uses the TTL port. The documentation supplied didn't mention setting the port directio registers (See the first couple of lines in the SensorInitializePort() routine). The EDU Bot did it for you but the RC requires that you do it yourself. If you want the source files PM me and I'll email you the files.

Gene F. Team 343 Metal in Motion

AAARRRGGG!!! The tabs all got removed when I posted the code! If anyone needs/wants the actual source code PM me.

#include "ifi_aliases.h"
#include "ifi_default.h"
#include "ifi_utilities.h"
#include "sensors.h"
#include "printf_lib.h"
// Added by Gene
#include <usart.h>
#include "delays.h"

SensorPackType Sensors;

/************************************************** *****************************
* FUNCTION NAME: InitializeSensorPort
* PURPOSE: Opens the serial port 2 for communicating with the scensors at
* 19.2k baud, 8 bits, no parity, one stop bit, and no flow control.
* CALLED FROM: user_routines.c
* ARGUMENTS: none
* RETURNS: void
************************************************** *****************************/
void SensorInitializePort (void)
{
// Set up TX pin as an output and RX as an input.
TRISGbits.TRISG1 = 0;
TRISGbits.TRISG2 = 1;

Open2USART(USART_TX_INT_OFF &
USART_RX_INT_OFF &
USART_ASYNCH_MODE &
USART_EIGHT_BIT &
USART_CONT_RX &
USART_BRGH_HIGH,
128);

Delay1KTCYx( 50 ); /* Settling time */
}

/* Code to read Bills device. */
/************************************************** *****************************
* FUNCTION NAME: ReadSensorPack
* PURPOSE: Talks to the sensor pack to read the current data
* CALLED FROM: user_routines.c
* ARGUMENTS: none
* RETURNS: void
************************************************** *****************************/
void SensorPackRead (void)
{
int i, j;
RCSTA2bits.CREN = 1; // Re-enable the receiver
// Send an STX to the sensor pack to tell it to send the data
putc2USART(STX);

// Loop for the number of characters in the sensor pack data
for ( j = 0; j < 8/*sizeof(SensorPackType)*/; j++ )
{
// Wait a finite amount of time for the next character to arrive.
for ( i = 0; i < 2500; i++ )
if ( DataRdy2USART())
break;

// If a character arrived (we didn't timeout)
if ( i != 2500 )
{
// Grab the next charcter from the USART and place it in our data structure
Sensors.chars[j] = getc2USART();
}
else
{
// If it failed then clear any possible errors
RCSTA2bits.CREN = 0; // Disable the receiver
RCSTA2bits.CREN = 1; // Re-enable the receiver
printf("Rx Fail DataRdy = %d\n",(int)DataRdy2USART()); /* printf EXAMPLE */
}
}
RCSTA2bits.CREN = 0; // Disable the receiver
// printf("x=%6d,y=%6d,pe=%6d,dd=%4d,ae=%4d\n", Sensors.LeftOdom, Sensors.RightOdom, Sensors.PosError, (int)(unsigned char)Sensors.DDCompass, (int)( char)Sensors.AngleError );
}

/************************************************** *****************************
* FUNCTION NAME: ensorEnterAutoMode
* PURPOSE: Puts the sensor pack into automatic mode sending the desired x
* and y coordiantes.
* Format of command: A<xl><xl><yl><yh>
* CALLED FROM: user_routines.c
* ARGUMENTS: none
* RETURNS: void
************************************************** *****************************/
void SensorEnterAutoMode (int x, int y)
{
volatile int i;
printf("x=%d y=%d\r",x,y);

while (Busy2USART());
putc2USART('A');
for(i=0;i<1000;i++);
while (Busy2USART());
putc2USART((char)(x & 0xff));
for(i=0;i<1000;i++);
while (Busy2USART());
putc2USART((char)((x >> 8) & 0xff));
for(i=0;i<1000;i++);
while (Busy2USART());
putc2USART((char)(y & 0xff));
for(i=0;i<1000;i++);
while (Busy2USART());
putc2USART((char)((y >> 8) & 0xff));
for(i=0;i<1000;i++);
while (Busy2USART());
putc2USART('\0');
}