Skip to content

[Backport ncs-v3.1-branch] [nrf fromlist] drivers: adc: nrfx: enable negative values for single-ended ADC readings #3182

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 1 commit into from
Closed

[Backport ncs-v3.1-branch] [nrf fromlist] drivers: adc: nrfx: enable negative values for single-ended ADC readings #3182

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
20 changes: 14 additions & 6 deletions drivers/adc/adc_nrfx_saadc.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -201,22 +201,24 @@ static int input_assign(nrf_saadc_input_t *pin_p,

if (channel_cfg->differential) {
if (channel_cfg->input_negative > ARRAY_SIZE(saadc_psels) ||
channel_cfg->input_negative < NRF_SAADC_AIN0 ||
(IS_ENABLED(CONFIG_NRF_PLATFORM_HALTIUM) &&
(channel_cfg->input_positive > NRF_SAADC_AIN7) !=
(channel_cfg->input_negative > NRF_SAADC_AIN7))) {
LOG_ERR("Invalid analog negative input number: %d",
channel_cfg->input_negative);
return -EINVAL;
}
*pin_n = saadc_psels[channel_cfg->input_negative];
*pin_n = channel_cfg->input_negative == NRF_SAADC_GND ?
NRF_SAADC_INPUT_DISABLED :
saadc_psels[channel_cfg->input_negative];
} else {
*pin_n = NRF_SAADC_INPUT_DISABLED;
}
#else
*pin_p = channel_cfg->input_positive;
*pin_n = channel_cfg->differential ? channel_cfg->input_negative
: NRF_SAADC_INPUT_DISABLED;
*pin_n = (channel_cfg->differential && (channel_cfg->input_negative != NRF_SAADC_GND))
? channel_cfg->input_negative
: NRF_SAADC_INPUT_DISABLED;
#endif
LOG_DBG("ADC positive input: %d", *pin_p);
LOG_DBG("ADC negative input: %d", *pin_n);
Expand Down Expand Up @@ -366,8 +368,14 @@ static int adc_nrfx_channel_setup(const struct device *dev,
* after ADC sequence ends.
*/
if (channel_cfg->differential) {
ch_cfg->mode = NRF_SAADC_MODE_DIFFERENTIAL;
m_data.single_ended_channels &= ~BIT(channel_cfg->channel_id);
if (channel_cfg->input_negative == NRF_SAADC_GND) {
ch_cfg->mode = NRF_SAADC_MODE_SINGLE_ENDED;
/* Do not mark as single-ended to not correct negative values. */
m_data.single_ended_channels &= ~BIT(channel_cfg->channel_id);
} else {
ch_cfg->mode = NRF_SAADC_MODE_DIFFERENTIAL;
m_data.single_ended_channels &= ~BIT(channel_cfg->channel_id);
}
} else {
ch_cfg->mode = NRF_SAADC_MODE_SINGLE_ENDED;
m_data.single_ended_channels |= BIT(channel_cfg->channel_id);
Expand Down
24 changes: 24 additions & 0 deletions include/zephyr/dt-bindings/adc/nrf-saadc.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,30 @@
#ifndef ZEPHYR_INCLUDE_DT_BINDINGS_ADC_NRF_SAADC_H_
#define ZEPHYR_INCLUDE_DT_BINDINGS_ADC_NRF_SAADC_H_

/**
* @brief Short ADC negative input to ground
*
* @details The nRF SAADC hardware only supports differential readings.
* The nRF SAADC SE (single ended) mode is differential with the negative
* input shorted to GND (ground). To use the nRF SAADC SE mode, set the
* negative input to NRF_SAADC_GND:
*
* @code{.dts}
* zephyr,input-positive = <NRF_SAADC_AIN3>;
* zephyr,input-negative = <NRF_SAADC_GND>;
* @endcode
*
* The nRF SAADC driver also supports using the nRF SAADC SE mode in
* emulated "single-ended" mode, as defined by zephyr. In this mode,
* negative readings will be clamped to 0 by software to emulate the
* behavior of an ADC in "single-ended" mode, as defined by zephyr. To
* do this, only define the positive input:
*
* @code{.dts}
* zephyr,input-positive = <NRF_SAADC_AIN3>;
* @endcode
*/
#define NRF_SAADC_GND 0
#define NRF_SAADC_AIN0 1
#define NRF_SAADC_AIN1 2
#define NRF_SAADC_AIN2 3
Expand Down
Loading