ADC Sample Time for Differential Channels Incorrectly Initialized when using HAL drivers
I'm using the HAL drivers to configure ADC1 Channel 3 as Differential and Channel 4 as Single Ended.
According to the reference manual (Figure 143) when ADC1 Channel 3 is differential, it is Channel 7 that becomes unavailable as it is used as INN3. This is further supported by the STM32CubeIDE which grays out Channel 7 when Channel 3 is made differential.
However, when the sample times registers are updated for the differential channels it is SMPR1 (SMP3 and SMP4) that are updated.
When Channel 4 sample time is configured SMPR1 (SMP4) gets overwritten.
In stm32h7xx_hal_adc.c (HAL_ADC_ConfigChannel) the sample times are updated for the channel:
LL_ADC_SetChannelSamplingTime(hadc->Instance, sConfig->Channel, sConfig->SamplingTime);
And if the channel is differential sets the sample time of the associated channel:
LL_ADC_SetChannelSamplingTime(hadc->Instance,
(uint32_t)(__LL_ADC_DECIMAL_NB_TO_CHANNEL((__LL_ADC_CHANNEL_TO_DECIMAL_NB((uint32_t)sConfig->Channel) + 1UL) & 0x1FUL)),
sConfig->SamplingTime);
Does this second channel's sampling time need to be set and should it be Channel 7 in this example?
If channels 10, 11, 12, 13, 16 or 18 are configured as differential it is the next channel that is used as the INN.