PWM does not start on TIM1

[BSerb]

I'm trying to use TIM1 to output a PWM signal on stm8s103f3 using the standard library (patched) with sdcc compiler.

The output goes high, but there's no signal.

#include "stm8s.h"
#include "stm8s_it.h" /* SDCC patch: required by SDCC for interrupts */
 
signed int PWM_DUTY = 500;
 
void main (void) {
 clock_setup();
 TIM1_Setup();
 GPIO_Setup();
 
 while(1) {
 TIM1_SetCompare1(PWM_DUTY);
 }
 
}
 
void GPIO_Setup(void) {
 GPIO_DeInit(GPIOC);
 GPIO_Init(GPIOC, GPIO_PIN_3 | GPIO_PIN_6, GPIO_MODE_OUT_PP_HIGH_FAST); //enable output on PC3
}
 
void clock_setup(void) {
 CLK_DeInit();
 CLK_LSICmd(DISABLE);
 CLK_HSECmd(DISABLE);
 CLK_HSICmd(ENABLE);
 CLK_ClockSwitchCmd(ENABLE);
 CLK_HSIPrescalerConfig(CLK_PRESCALER_HSIDIV1); //8MHz clock
 CLK_SYSCLKConfig(CLK_PRESCALER_CPUDIV1);
 CLK_ClockSwitchConfig(CLK_SWITCHMODE_AUTO, CLK_SOURCE_HSI, DISABLE, CLK_CURRENTCLOCKSTATE_ENABLE);
 CLK_PeripheralClockConfig(CLK_PERIPHERAL_TIMER1, ENABLE);
}
 
void TIM1_Setup(void) {
 TIM1_DeInit();
 TIM1_TimeBaseInit(16, TIM1_COUNTERMODE_UP, 1000, 1);
 TIM1_OC1Init(TIM1_OCMODE_PWM1, TIM1_OUTPUTSTATE_ENABLE, TIM1_OUTPUTNSTATE_ENABLE, 1000, TIM1_OCPOLARITY_LOW, TIM1_OCNPOLARITY_LOW, TIM1_OCIDLESTATE_RESET, TIM1_OCNIDLESTATE_RESET);
 TIM1_CtrlPWMOutputs(ENABLE);
 TIM1_Cmd(ENABLE);
}

Am I missing something or is it the library?

[Artur IWANICKI]

Hello,

You have configured the same value for period and pulse, thus you cannot see PWM on the pin.

Please replace 4th argument (1000) within TIM1_OC1Init() with PWM_DUTY and it should work.

Best Regards,

Artur

[Xavi92]

Also, take into account pin 16 (aka PC6) only operates as TIM1_CH1 when option bit OPT2.AFR0 is set and NOPT2.NAFR0 is cleared. Otherwise, you will get no signal since that pin would be operating as SPI_MOSI instead.

[Willunen]

Thanks! Your remark about the option-bits did help me, as I was wondering why TIM1 CH1 didn't produce any output.

(But that pin would be MOSI only if SPI was enabled, right?)

Wilko

[Xavi92]

Exactly. According to the STM8S003K3/F3 datasheet, the default function after reset for that pin is PC6, so it acts as a simple GPIO pin.