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analog: nrf52: Add acquisition time configuration function #526

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analog: nrf52: Add acquisition time configuration function #526

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36 changes: 36 additions & 0 deletions cores/nRF5/wiring_analog.h
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Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,42 @@ typedef enum _eAnalogReference
} eAnalogReference ;
#endif

#if defined(NRF52_SERIES)
/*
* \brief Acquisition time enumeration. To be used with \ref analogAcquisitionTime
*/
typedef enum _eAcquisitionTime
{
AT_DEFAULT,
AT_3us,
AT_5us,
AT_10us,
AT_15us,
AT_20us,
AT_40us
} eAcquisitionTime ;

/*
* \brief Set the acquisition time of the ADC.
* Default value: 3us.
* Acquision time should match the maximum source resistance of the signal.
* See the '37.9 Acquisition time' chapter of the datasheet for more details.
*
* <table>
* <caption>Acquisition Time</caption>
* <tr><th>Acquisition Time<th>Maximum source resistance
* <tr><td>3us <td>10kOhm
* <tr><td>5us <td>40kOhm
* <tr><td>10us <td>100kOhm
* <tr><td>15us <td>200kOhm
* <tr><td>20us <td>400kOhm
* <tr><td>40us <td>800kOhm
* </table>
*
* \param ulMmode
*/
extern void analogAcquisitionTime( eAcquisitionTime ulMode );
#endif

/*
* \brief Configures the reference voltage used for analog input (i.e. the value used as the top of the input range).
Expand Down
34 changes: 33 additions & 1 deletion cores/nRF5/wiring_analog_nRF52.c
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@ extern "C" {

static uint32_t saadcReference = SAADC_CH_CONFIG_REFSEL_Internal;
static uint32_t saadcGain = SAADC_CH_CONFIG_GAIN_Gain1_5;
static uint32_t saadcAcqTime = SAADC_CH_CONFIG_TACQ_3us;

static NRF_PWM_Type* pwms[PWM_COUNT] = {
NRF_PWM0,
Expand Down Expand Up @@ -101,6 +102,37 @@ void analogReference( eAnalogReference ulMode )
}
}

void analogAcquisitionTime( eAcquisitionTime ulMode )
{
switch ( ulMode ) {
case AT_DEFAULT:
case AT_3us:
saadcAcqTime = SAADC_CH_CONFIG_TACQ_3us;
break;

case AT_5us:
saadcAcqTime = SAADC_CH_CONFIG_TACQ_5us;
break;

case AT_10us:
saadcAcqTime = SAADC_CH_CONFIG_TACQ_10us;
break;

case AT_15us:
saadcAcqTime = SAADC_CH_CONFIG_TACQ_15us;
break;

case AT_20us:
saadcAcqTime = SAADC_CH_CONFIG_TACQ_20us;
break;

case AT_40us:
default:
saadcAcqTime = SAADC_CH_CONFIG_TACQ_40us;
break;
}
}

uint32_t analogRead( uint32_t ulPin )
{
uint32_t pin = SAADC_CH_PSELP_PSELP_NC;
Expand Down Expand Up @@ -176,7 +208,7 @@ uint32_t analogRead( uint32_t ulPin )
| ((SAADC_CH_CONFIG_RESP_Bypass << SAADC_CH_CONFIG_RESN_Pos) & SAADC_CH_CONFIG_RESN_Msk)
| ((saadcGain << SAADC_CH_CONFIG_GAIN_Pos) & SAADC_CH_CONFIG_GAIN_Msk)
| ((saadcReference << SAADC_CH_CONFIG_REFSEL_Pos) & SAADC_CH_CONFIG_REFSEL_Msk)
| ((SAADC_CH_CONFIG_TACQ_3us << SAADC_CH_CONFIG_TACQ_Pos) & SAADC_CH_CONFIG_TACQ_Msk)
| ((saadcAcqTime << SAADC_CH_CONFIG_TACQ_Pos) & SAADC_CH_CONFIG_TACQ_Msk)
| ((SAADC_CH_CONFIG_MODE_SE << SAADC_CH_CONFIG_MODE_Pos) & SAADC_CH_CONFIG_MODE_Msk);
NRF_SAADC->CH[0].PSELN = pin;
NRF_SAADC->CH[0].PSELP = pin;
Expand Down