I’m attempting to configure TIM3 to count up on pulses received from an external trigger on TIM3CH1 but I'm not seeing CNT change.
I’ve followed the sample instructions in the datasheet (RM3099 Rev 3) (for External clock source mode 2--all registers mentioned below are set as directed and those that aren't are in their default state):
For example, to configure the upcounter to count each 2 rising edges on ETR, use the
following procedure:
- Select the proper ETR source (internal or external) with the ETRSEL[3:0] bits in the TIMx_AF1 register.
- As no filter is needed in this example, write ETF[3:0]=0000 in the TIMx_SMCR register.
- Set the prescaler by writing ETPS[1:0]=01 in the TIMx_SMCR register
- Select rising edge detection on the ETR pin by writing ETP=0 in the TIMx_SMCR register
- Enable external clock mode 2 by writing ECE=1 in the TIMx_SMCR register.
- Enable the counter by writing CEN=1 in the TIMx_CR1 register.
My specific settings are:
- AF1:ETRSEL = b’0000 (ETR input is connected to I/O)--I've got the output connected to TIM3_ETR and have it configured as such.
I've also tried external trigger mode 1, following these instructions from the datasheet:
For example, to configure the upcounter to count in response to a rising edge on the TI2
input, use the following procedure:
- Select the proper TI2x source (internal or external) with the TI2SEL[3:0] bits in the TIMx_TISEL register.
- Configure channel 2 to detect rising edges on the TI2 input by writing CC2S= ‘01 in the TIMx_CCMR1 register.
- Configure the input filter duration by writing the IC2F[3:0] bits in the TIMx_CCMR1 register (if no filter is needed, keep IC2F=0000).
- Select rising edge polarity by writing CC2P=0 and CC2NP=0 and CC2NP=0 in the TIMx_CCER register.
- Configure the timer in external clock mode 1 by writing SMS=111 in the TIMx_SMCR register.
- Select TI2 as the input source by writing TS=00110 in the TIMx_SMCR register.
- Enable the counter by writing CEN=1 in the TIMx_CR1 register.
I adapted these to use TI1 and had the pin connected to PC6 (TIM3CH1, configured as such). AN4776 has some detail to add to the examples from the datasheet, but there wasn't anything in there that really helped.
I have a 1kHz 50% duty cycle square wave generated from TIM1 that I’m feeding into TIM3CH1 (which I’ve also had produce an output to check electrical correctness). I’d expect to see CNT increasing, but I’m not. I feel like there's something fundamental I'm missing here--I'd appreciate any help you can provide.
