// The voltage that a reading of 1 from `analogRead` actually represents
JsVarFloat jshReadVRef() {
#ifdef NRF52
nrf_saadc_channel_config_t config;
config.acq_time = NRF_SAADC_ACQTIME_3US;
config.gain = NRF_SAADC_GAIN1_6; // 1/6 of input volts
config.mode = NRF_SAADC_MODE_SINGLE_ENDED;
config.pin_p = NRF_SAADC_INPUT_VDD;
config.pin_n = NRF_SAADC_INPUT_VDD;
config.reference = NRF_SAADC_REFERENCE_INTERNAL; // 0.6v reference.
config.resistor_p = NRF_SAADC_RESISTOR_DISABLED;
config.resistor_n = NRF_SAADC_RESISTOR_DISABLED;
// make reading
nrf_saadc_enable();
nrf_saadc_resolution_set(NRF_SAADC_RESOLUTION_14BIT);
nrf_saadc_channel_init(0, &config);
return 6.0 * (nrf_analog_read() * 0.6 / 8192.0);
#else
const nrf_adc_config_t nrf_adc_config = {
NRF_ADC_CONFIG_RES_10BIT,
NRF_ADC_CONFIG_SCALING_INPUT_FULL_SCALE,
NRF_ADC_CONFIG_REF_VBG }; // internal reference
nrf_adc_configure( (nrf_adc_config_t *)&nrf_adc_config);
return 1.2 / nrf_adc_convert_single(ADC_CONFIG_PSEL_AnalogInput0);
#endif
}
ret_code_t nrf_drv_saadc_channel_init(uint8_t channel,
nrf_saadc_channel_config_t const * const p_config)
{
ASSERT(m_cb.state != NRF_DRV_STATE_UNINITIALIZED);
ASSERT(channel < NRF_SAADC_CHANNEL_COUNT);
// Oversampling can be used only with one channel.
ASSERT((nrf_saadc_oversample_get() == NRF_SAADC_OVERSAMPLE_DISABLED) ||
(m_cb.active_channels == 0));
ASSERT((p_config->pin_p <= NRF_SAADC_INPUT_VDD) &&
(p_config->pin_p > NRF_SAADC_INPUT_DISABLED));
ASSERT(p_config->pin_n <= NRF_SAADC_INPUT_VDD);
// A channel can only be initialized if the driver is in the idle state.
if (m_cb.adc_state != NRF_SAADC_STATE_IDLE)
{
return NRF_ERROR_BUSY;
}
if (!m_cb.psel[channel].pselp)
{
++m_cb.active_channels;
}
m_cb.psel[channel].pselp = p_config->pin_p;
m_cb.psel[channel].pseln = p_config->pin_n;
nrf_saadc_channel_init(channel, p_config);
nrf_saadc_channel_input_set(channel, p_config->pin_p, p_config->pin_n);
return NRF_SUCCESS;
}
/// Returns a quickly-read analog value in the range 0-65535
int jshPinAnalogFast(Pin pin) {
if (pinInfo[pin].analog == JSH_ANALOG_NONE) return 0;
#ifdef NRF52
// sanity checks for channel
assert(NRF_SAADC_INPUT_AIN0 == 1);
assert(NRF_SAADC_INPUT_AIN1 == 2);
assert(NRF_SAADC_INPUT_AIN2 == 3);
nrf_saadc_input_t ain = 1 + (pinInfo[pin].analog & JSH_MASK_ANALOG_CH);
nrf_saadc_channel_config_t config;
config.acq_time = NRF_SAADC_ACQTIME_3US;
config.gain = NRF_SAADC_GAIN1_4; // 1/4 of input volts
config.mode = NRF_SAADC_MODE_SINGLE_ENDED;
config.pin_p = ain;
config.pin_n = ain;
config.reference = NRF_SAADC_REFERENCE_VDD4; // VDD/4 as reference.
config.resistor_p = NRF_SAADC_RESISTOR_DISABLED;
config.resistor_n = NRF_SAADC_RESISTOR_DISABLED;
// make reading
nrf_saadc_enable();
nrf_saadc_resolution_set(NRF_SAADC_RESOLUTION_8BIT);
nrf_saadc_channel_init(0, &config);
return nrf_analog_read() << 8;
#else
const nrf_adc_config_t nrf_adc_config = {
NRF_ADC_CONFIG_RES_8BIT, // 8 bit for speed (hopefully!)
NRF_ADC_CONFIG_SCALING_INPUT_FULL_SCALE,
NRF_ADC_CONFIG_REF_VBG }; // internal reference
nrf_adc_configure( (nrf_adc_config_t *)&nrf_adc_config);
// sanity checks for nrf_adc_convert_single...
assert(ADC_CONFIG_PSEL_AnalogInput0 == 1);
assert(ADC_CONFIG_PSEL_AnalogInput1 == 2);
assert(ADC_CONFIG_PSEL_AnalogInput2 == 4);
// make reading
return nrf_adc_convert_single(1 << (pinInfo[pin].analog & JSH_MASK_ANALOG_CH)) << 8;
#endif
}
