Other Parts Discussed in Thread: TMS320F2812
Hello,
An odd issue comes up in the code that is written for TMS320F2812 and attached below. The program just outputs a square wave that is generated with timer 1 in event manager A. Before setting up the required registers for this task, I configure all GPIO pins as digital outputs and set them to 0 to not have the floating pins as inputs (as recommended in the hardware design guidelines).
The problem is now that the code does not work if bit 0 of GPIO D (T1CTRIP_PDPINTA) is cleared. Please see the highlighted line in the code below. If FFFF is written into the clear register of GPIO D (like in all the others), the square wave is not output any more. Instead the signal is constantly high. If the LSB of GPIO D is not cleared on the other hand, by writing FFFE, then it works fine. I am aware that the trip function can set the compare output to high Z but still find the behaviour surprising because GPDMUX is set to 0 before and indeed is 0 at runtime, telling the pin to have the digital I/O function and not the peripheral functionality, and moreover the bit is supposed to be 0 after reset anyway.
What could be the reason?
Regards,
Adrian
/*
* timertry_T1PWM
* main.c
*
* use the GP timer compare unit of event manager A, timer 1, to get a PWM signal with f = 20 kHz
* GP timer 1 uses its own compare functionality (output T1PWM)
* output pin: T1PWM (pin 15)
*
*/
#include "DSP281x_Device.h"
#include "math.h"
extern void InitSysCtrl(void);
void main() {
float d=0.77;
InitSysCtrl();
// configure all GPIO pins as digital outputs and set to 0
EALLOW;
GpioMuxRegs.GPAMUX.all=0;
GpioMuxRegs.GPBMUX.all=0;
GpioMuxRegs.GPDMUX.all=0;
GpioMuxRegs.GPEMUX.all=0;
GpioMuxRegs.GPFMUX.all=0;
GpioMuxRegs.GPGMUX.all=0;
GpioMuxRegs.GPADIR.all=0xFFFF;
GpioMuxRegs.GPBDIR.all=0xFFFF;
GpioMuxRegs.GPDDIR.all=0xFFFF;
GpioMuxRegs.GPEDIR.all=0xFFFF;
GpioMuxRegs.GPFDIR.all=0xFFFF;
GpioMuxRegs.GPGDIR.all=0xFFFF;
GpioDataRegs.GPACLEAR.all=0xFFFF;
GpioDataRegs.GPBCLEAR.all=0xFFFF;
GpioDataRegs.GPDCLEAR.all=0xFFFE; // oddity here
If FFFF is written into the clear register, the program does not work any more.
GpioDataRegs.GPECLEAR.all=0xFFFF;
GpioDataRegs.GPFCLEAR.all=0xFFFF;
GpioDataRegs.GPGCLEAR.all=0xFFFF;
EDIS;
// configure required GPIO pins as peripheral (here: timer) outputs (digital I/O)
EALLOW;
GpioMuxRegs.GPAMUX.bit.T1PWM_GPIOA6=1;
EDIS;
// GP timer 1 setup
EvaRegs.T1CON.bit.FREE=0; // stop immediately on emulation suspend
EvaRegs.T1CON.bit.SOFT=0; // ... second part of it
EvaRegs.T1CON.bit.TMODE=2; // continuous up-counting mode
EvaRegs.T1CON.bit.TPS=0; // input clock prescaler, corresponds to factor 1
EvaRegs.T1CON.bit.TENABLE=1; // enable timer
EvaRegs.T1CON.bit.TCLKS10=0; // use HSPCLK as clock
EvaRegs.T1CON.bit.TCLD10=0; // reload compare register T1CMPR at beginning of switching period
EvaRegs.T1CON.bit.TECMPR=1; // enable timer compare
EvaRegs.T1PR=7499; // period register = 150MHz/20kHz-1 (HISPCP = 1, TPS = 0)
EvaRegs.T1CMPR=floor(EvaRegs.T1PR*d); // compare register for T1PWM
EvaRegs.T1CNT=0; // initialize counter register
// GP timer control register of EVA (for T1PWM)
EvaRegs.GPTCONA.bit.T1CTRIPE=0; // disable trip function that can drive output to high Z
EvaRegs.GPTCONA.bit.TCMPOE=1; // enable compare output
EvaRegs.GPTCONA.bit.T1TOADC=0; // don't set off ADC
EvaRegs.GPTCONA.bit.TCMPOE=1; // enable timer compare outputs
EvaRegs.GPTCONA.bit.T1CMPOE=1; // enable timer 1 compare outputs
EvaRegs.GPTCONA.bit.T1PIN=1; // polarity of T1PWM (1 = active L, 2 = active H)
while(1){
;
}
}
