FTM QuadratureDecoder

LArmstrong1985 — Mon, 30 Mar 2020 13:55:37 GMT

I'm trying to read the quadrature signals generated by motor's encoder.

I implemented a solution similar to the example "ftm_quad_decoder" with the difference that I use a global variable to add the values read to each timer interrupt, and instead of PIT timer I use FTM timer which trips very quickly (every 100 ms) so as not to have overflow problems.

This is my code:

void EncoderTimerInit(MotorStatus* motorStatus) {
hal_timer_handle_t halTimerHandle = (hal_timer_handle_t) (&halTimerHandleBuffer[0]);
hal_timer_config_t halTimerConfig;
halTimerConfig.timeout = 100;
halTimerConfig.srcClock_Hz = CLOCK_GetBusClkFreq();
halTimerConfig.instance = 1;
HAL_TimerInit(halTimerHandle, &halTimerConfig);
HAL_TimerInstallCallback(halTimerHandle, &TimerCallBack, (void*) (motorStatus));
HAL_TimerEnable(halTimerHandle);
}
void TimerCallBack(void* param)
{
MotorStatus* motorStatus = (MotorStatus*) param;
volatile int16_t value = 0;
value = FTM_GetQuadDecoderCounterValue(QUAD_DECODER_COUNTER);
FTM_ClearQuadDecoderCounterValue(QUAD_DECODER_COUNTER);
encoder_count += value;
}

Unfortunately I have seen that in this way the value read is quite far from what is expected.

Could it be that instructions FTM_GetQuadDecoderCounterValue e FTM_ClearQuadDecoderCounterValue take some time so while motors are in movement I lose some values?

Is better to leave timer free running (MOD = 0xFFFF) and use overlap callback?

In this case how a can how can I understand the verse of the overflow? I saw in the "ftm_quad_decoder" example are defined several variables (dir_when_overflow, counter_overflow_flag, counter_overflow_count) that are defined but now used, therefore not showing this type of use...

Thank you very much!

Re: FTM QuadratureDecoder

FelipeGarcia — Thu, 02 Apr 2020 16:09:32 GMT

Hello Fabio,

Could you please let me know which device are you working on?

Regards,

Felipe

topic FTM QuadratureDecoder in Kinetis Microcontrollers

FTM QuadratureDecoder

Re: FTM QuadratureDecoder