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drivers: adc_nrfx_saadc: Remove dead and misleading code

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For a long time (since version 3.3.0) nrfx contained an incorrectly
defined symbol NRF_SAADC_8BIT_SAMPLE_WIDTH that was set to 8 for nRF54L
and nRF54H Series SoCs, which was probably only true for very early
engineering revisions of those. Based on this, the adc_nrfx_saadc driver
was incorrectly writing consecutive 8-bit samples in supplied buffers,
cutting off the highest 8 bits of the results. And for sequences with
multiple channels, it was even causing that the results written as
16-bit words by hardware were partially overwritten in next iteration.

In nrfx 3.12.0 (see commit f46798fa55)
this was finally corrected - the symbol is now deprecated and it is
always set to 16. This commit is a follow-up to the above and removes
parts of adc_nrfx_saadc that now became dead code to prevent further
confusion regarding 8-bit sampling.

Signed-off-by: Andrzej Głąbek <andrzej.glabek@nordicsemi.no>
This commit is contained in:
Andrzej Głąbek 2025-06-16 07:53:43 +02:00 • committed by Benjamin Cabé
commit 616ec7522c
1 changed files with 5 additions and 26 deletions
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31
drivers/adc/adc_nrfx_saadc.c
View file

@ -141,12 +141,8 @@ static struct driver_data m_data = {
};
/* Helper function to convert number of samples to the byte representation. */
static uint32_t samples_to_bytes(const struct adc_sequence *sequence, uint16_t number_of_samples)
static uint32_t samples_to_bytes(uint16_t number_of_samples)
{
if (NRF_SAADC_8BIT_SAMPLE_WIDTH == 8 && sequence->resolution == 8) {
return number_of_samples;
}
return number_of_samples * 2;
}
@ -410,11 +406,11 @@ static void adc_context_update_buffer_pointer(struct adc_context *ctx,
if (!repeat) {
#if defined(ADC_BUFFER_IN_RAM)
m_data.user_buffer = (uint8_t *)m_data.user_buffer +
samples_to_bytes(&ctx->sequence, nrfy_saadc_amount_get(NRF_SAADC));
samples_to_bytes(nrfy_saadc_amount_get(NRF_SAADC));
#else
nrf_saadc_value_t *buffer =
(uint8_t *)nrf_saadc_buffer_pointer_get(NRF_SAADC) +
samples_to_bytes(&ctx->sequence, nrfy_saadc_amount_get(NRF_SAADC));
samples_to_bytes(nrfy_saadc_amount_get(NRF_SAADC));
nrfy_saadc_buffer_pointer_set(NRF_SAADC, buffer);
#endif
}
@ -501,7 +497,7 @@ static int check_buffer_size(const struct adc_sequence *sequence,
{
size_t needed_buffer_size;
needed_buffer_size = samples_to_bytes(sequence, active_channels);
needed_buffer_size = samples_to_bytes(active_channels);
if (sequence->options) {
needed_buffer_size *= (1 + sequence->options->extra_samplings);
@ -546,7 +542,6 @@ static int start_read(const struct device *dev,
{
int error;
uint32_t selected_channels = sequence->channels;
uint8_t resolution = sequence->resolution;
uint8_t active_channels;
uint8_t channel_id;
nrf_saadc_burst_t burst;
@ -576,22 +571,6 @@ static int start_read(const struct device *dev,
channel_id);
return -EINVAL;
}
/* Signal an error if the channel is configured as
* single ended with a resolution which is identical
* to the sample bit size. The SAADC's "single ended"
* mode is really differential mode with the
* negative input tied to ground. We can therefore
* observe negative values if the positive input falls
* below ground. If the sample bitsize is larger than
* the resolution, we can detect negative values and
* correct them to 0 after the sequencen has ended.
*/
if ((m_data.single_ended_channels & BIT(channel_id)) &&
(NRF_SAADC_8BIT_SAMPLE_WIDTH == 8 && resolution == 8)) {
LOG_ERR("Channel %u invalid single ended resolution",
channel_id);
return -EINVAL;
}
/* When oversampling is used, the burst mode needs to
* be activated. Unfortunately, this mode cannot be
* activated permanently in the channel setup, because
@ -713,7 +692,7 @@ static void saadc_irq_handler(const struct device *dev)
#if defined(ADC_BUFFER_IN_RAM)
memcpy(m_data.user_buffer, m_data.samples_buffer,
samples_to_bytes(&m_data.ctx.sequence, m_data.active_channels));
samples_to_bytes(m_data.active_channels));
#endif
adc_context_on_sampling_done(&m_data.ctx, dev);