Timer 1, Channel 3 Lower Than Expected Output Voltage

[Nevyn]

Posted on September 04, 2012 at 14:41

I have been developing some applications for the STM8S103F3 which I have on breadboard and I have recently transferred one of the projects to the STM8S Discovery board and I am finding a difference in behaviour which I cannot work out.

The program uses PWM Mode 2 to output a 60 uS square wave on timer 1 channel3.  On the STM8S103F3 on breadboard the program works fine and I get a 0 to 3.3V square wave.On the Discovery board I have the square wave with the right frequency but the output voltage is only 280 mV peak-to-peak.  The only things I have connected to the Discovery board are the USB connection and the scope connected to the timer output and ground.I am using IAR as the development environment and I have modified the include files and project options accordingly.Any ideas where I could be going wrong? Am I correct in assuming that if the app runs on the STM8S103F3 then it will run on the Discovery board assuming I change the include file and target chip?The code for the application is included below.Regards,Mark&sharpinclude <intrinsics.h>&sharpinclude <iostm8s103f3.h>////  Setup the system clock to run at 16MHz using the internal oscillator.//void InitialiseSystemClock(){    CLK_ICKR = 0;                       //  Reset the Internal Clock Register.    CLK_ICKR_HSIEN = 1;                 //  Enable the HSI.    CLK_ECKR = 0;                       //  Disable the external clock.    while (CLK_ICKR_HSIRDY == 0);       //  Wait for the HSI to be ready for use.    CLK_CKDIVR = 0;                     //  Ensure the clocks are running at full speed.    CLK_PCKENR1 = 0xff;                 //  Enable all peripheral clocks.    CLK_PCKENR2 = 0xff;                 //  Ditto.    CLK_CCOR = 0;                       //  Turn off CCO.    CLK_HSITRIMR = 0;                   //  Turn off any HSIU trimming.    CLK_SWIMCCR = 0;                    //  Set SWIM to run at clock / 2.    CLK_SWR = 0xe1;                     //  Use HSI as the clock source.    CLK_SWCR = 0;                       //  Reset the clock switch control register.    CLK_SWCR_SWEN = 1;                  //  Enable switching.    while (CLK_SWCR_SWBSY != 0);        //  Pause while the clock switch is busy.}////  Initialise Timer 1.//void InitialiseTimer1(){    TIM1_CR1 = 0;    TIM1_CR2 = 0;    TIM1_SMCR = 0;    TIM1_ETR = 0;    TIM1_IER  = 0;    TIM1_SR2  = 0;    TIM1_CCER1 = 0;    TIM1_CCER2 = 0;    TIM1_CCMR1 = 0;    TIM1_CCMR2 = 0;    TIM1_CCMR3 = 0;    TIM1_CCMR4 = 0;    TIM1_CCER1 = 0;    TIM1_CCER2 = 0;    TIM1_CCMR1 = 0;    TIM1_CCMR2 = 0;    TIM1_CCMR3 = 0;    TIM1_CCMR4 = 0;    TIM1_CNTRH = 0;    TIM1_CNTRL = 0;    TIM1_PSCRH = 0;    TIM1_PSCRL = 0;    TIM1_ARRH  = 0;    TIM1_ARRL  = 0;    TIM1_CCR1H = 0;    TIM1_CCR1L = 0;    TIM1_CCR2H = 0;    TIM1_CCR2L = 0;    TIM1_CCR3H = 0;    TIM1_CCR3L = 0;    TIM1_CCR4H = 0;    TIM1_CCR4L = 0;    TIM1_OISR  = 0;    TIM1_EGR   = 0x01;    TIM1_DTR   = 0;    TIM1_BKR   = 0;    TIM1_RCR   = 0;    TIM1_SR1   = 0;}////  Set up Timer 1, channel 3 to output a single pulse lasting 30 uS.//void SetupTimer1(){    TIM1_ARRH = 0x03;       //  Reload counter = 960    TIM1_ARRL = 0xc0;    TIM1_PSCRH = 0;         //  Prescalar = 0 (i.e. 1)    TIM1_PSCRL = 0;    TIM1_CR1_DIR = 0;       //  Up counter.    TIM1_CR1_CMS = 0;       //  Edge aligned counter.    TIM1_RCR = 0;           //  No repetition.    //    //  Now configure Timer 1, channel 3.    //    TIM1_CCMR3_OC3M = 7;    //  Set up to use PWM mode 2.    TIM1_CCER2_CC3E = 1;    //  Output is enabled.    TIM1_CCER2_CC3P = 0;    //  Active is defined as high.    TIM1_CCR3H = 0x01;      //  480 = 50% duty cycle (based on TIM1_ARR).    TIM1_CCR3L = 0xe0;    TIM1_BKR_MOE = 1;       //  Enable the main output.//    TIM1_CR1_OPM = 1;    TIM1_CR1_CEN = 1;}////  Main program loop.//void main(){    //    //  Initialise the system.    //    __disable_interrupt();    InitialiseSystemClock();    InitialiseTimer1();    SetupTimer1();    __enable_interrupt();    while (1)    {        __wait_for_interrupt();    }} #stm8s103f3-discovery-timer

[Nevyn]

Posted on October 06, 2012 at 11:37

Worked this one out (with the help from a friend).  The problem is that the pin outputting the Tim1Ch3 signal is connected to the touch sensor.  I changed the channel to Tim1Ch4 and everything is looking good.

I could have removed the connection as the manual tells you how to do this but I thought I'd try the non-invasive route first.Regards,Mark

[Aaron Derbyshire]

Posted on July 04, 2017 at 13:38

hi,

I am having a similar issue with Timer 2, channel 2 on Port D Pin 3.

I've double checked the schematic fir the STM8S discovery board and this pin is unused.

My timer configuration is as follows:

void TIM2_PWM(void)

{ /* SET PRESCALER */ TIM2.PSCR = 0; /* SET ARR */ TIM2.ARRH = 0x4E; TIM2.ARRL = 0x1F; /* CH1 ENABLED ACTIVE LOW POLARITY */ TIM2.CCER1 = 0x30; /* PWM2 */ TIM2.CCMR2 = 0x70; /* SET PULSE WIDTH */ TIM2.CCR2H = 0x3E; TIM2.CCR2L = 0x80; /* ENABLE PRELOAD REGISTER */ TIM2.CCMR2 |= 0x08; /* TIM2_ARR PRELOAD ENABLE */ TIM2.CR1 |= 0x80; /* TIM2 ENABLE */  TIM2.CR1 |= 0x01;}

The resulting output is generating a 800Hz signal with a 80% duty cycle, as desired. However, the waveform is peaking at 360mV. I have that pin configured as a push-pull output at 10Mhz.

Any help would be greatly appreciated.

Regards

Aaron