Measure voltage supplied to chip

ports/atmel-samd/common-hal/microcontroller/Processor.c

@@ -72,6 +72,8 @@
 #define INT1V_DIVIDER_1000 1000.0
 #define ADC_12BIT_FULL_SCALE_VALUE_FLOAT 4095.0
 
+// channel argument (ignored in calls below)
+#define IGNORED_CHANNEL 0
 
 // Decimal to fraction conversion. (adapted from ASF sample).
 STATIC float convert_dec_to_frac(uint8_t val) {
@@ -196,14 +198,12 @@ float common_hal_mcu_processor_get_temperature(void) {
 
     adc_sync_set_resolution(&adc, ADC_CTRLB_RESSEL_12BIT_Val);
     adc_sync_set_reference(&adc, ADC_REFCTRL_REFSEL_INT1V_Val);
-    // Channel passed in adc_sync_enable_channel is actually ignored (!).
-    adc_sync_enable_channel(&adc, ADC_INPUTCTRL_MUXPOS_TEMP_Val);
+    // Channel arg is ignored.
+    adc_sync_enable_channel(&adc, IGNORED_CHANNEL);
     adc_sync_set_inputs(&adc,
                         ADC_INPUTCTRL_MUXPOS_TEMP_Val,   // pos_input
                         ADC_INPUTCTRL_MUXNEG_GND_Val,    // neg_input
-                        ADC_INPUTCTRL_MUXPOS_TEMP_Val);  // channel channel (this arg is ignored (!))
-
-    adc_sync_set_resolution(&adc, ADC_CTRLB_RESSEL_12BIT_Val);
+                        IGNORED_CHANNEL);                // channel (ignored)
 
     hri_adc_write_CTRLB_PRESCALER_bf(adc.device.hw, ADC_CTRLB_PRESCALER_DIV32_Val);
     hri_adc_write_SAMPCTRL_SAMPLEN_bf(adc.device.hw, ADC_TEMP_SAMPLE_LENGTH);
@@ -222,62 +222,100 @@ float common_hal_mcu_processor_get_temperature(void) {
     // like voltage reference / ADC channel change"
     // Empirical observation shows the first reading is quite different than subsequent ones.
 
-    // The channel listed in adc_sync_read_channel is actually ignored(!).
-    // Must be set as above with adc_sync_set_inputs.
-    adc_sync_read_channel(&adc, ADC_INPUTCTRL_MUXPOS_TEMP_Val, ((uint8_t*) &value), 2);
-    adc_sync_read_channel(&adc, ADC_INPUTCTRL_MUXPOS_TEMP_Val, ((uint8_t*) &value), 2);
+    // Channel arg is ignored.
+    adc_sync_read_channel(&adc, IGNORED_CHANNEL, ((uint8_t*) &value), 2);
+    adc_sync_read_channel(&adc, IGNORED_CHANNEL, ((uint8_t*) &value), 2);
 
     adc_sync_deinit(&adc);
     return calculate_temperature(value);
 #endif // SAMD21
 
 #ifdef SAMD51
     adc_sync_set_resolution(&adc, ADC_CTRLB_RESSEL_12BIT_Val);
-    // Reference voltage choice is a guess. It's not specified in the datasheet that I can see.
+    // Using INTVCC0 as the reference voltage.
     // INTVCC1 seems to read a little high.
-    // INTREF doesn't work: ADC hangs BUSY.
+    // INTREF doesn't work: ADC hangs BUSY. It's supposed to work, but does not.
+    // The SAME54 example from Atmel START implicitly uses INTREF.
     adc_sync_set_reference(&adc, ADC_REFCTRL_REFSEL_INTVCC0_Val);
 
-    // If ONDEMAND=1, we don't need to use the VREF.TSSEL bit to choose PTAT and CTAT.
     hri_supc_set_VREF_ONDEMAND_bit(SUPC);
+    // Enable temperature sensor.
     hri_supc_set_VREF_TSEN_bit(SUPC);
+    hri_supc_set_VREF_VREFOE_bit(SUPC);
 
-    // Channel passed in adc_sync_enable_channel is actually ignored (!).
-    adc_sync_enable_channel(&adc, ADC_INPUTCTRL_MUXPOS_PTAT_Val);
+    // Channel arg is ignored.
+    adc_sync_enable_channel(&adc, IGNORED_CHANNEL);
     adc_sync_set_inputs(&adc,
                         ADC_INPUTCTRL_MUXPOS_PTAT_Val,   // pos_input
                         ADC_INPUTCTRL_MUXNEG_GND_Val,    // neg_input
-                        ADC_INPUTCTRL_MUXPOS_PTAT_Val);  // channel (this arg is ignored (!))
+                        IGNORED_CHANNEL);                // channel (ignored)
 
     // Read both temperature sensors.
     volatile uint16_t ptat;
     volatile uint16_t ctat;
 
-    // The channel listed in adc_sync_read_channel is actually ignored(!).
-    // Must be set as above with adc_sync_set_inputs.
-    // Read twice for stability (necessary?)
-    adc_sync_read_channel(&adc, ADC_INPUTCTRL_MUXPOS_PTAT_Val, ((uint8_t*) &ptat), 2);
-    adc_sync_read_channel(&adc, ADC_INPUTCTRL_MUXPOS_PTAT_Val, ((uint8_t*) &ptat), 2);
+    // Read twice for stability (necessary?).
+    adc_sync_read_channel(&adc, IGNORED_CHANNEL, ((uint8_t*) &ptat), 2);
+    adc_sync_read_channel(&adc, IGNORED_CHANNEL, ((uint8_t*) &ptat), 2);
 
     adc_sync_set_inputs(&adc,
                         ADC_INPUTCTRL_MUXPOS_CTAT_Val,   // pos_input
                         ADC_INPUTCTRL_MUXNEG_GND_Val,    // neg_input
-                        ADC_INPUTCTRL_MUXPOS_CTAT_Val);  // channel (this arg is ignored (!))
-
-    // Channel passed in adc_sync_enable_channel is actually ignored (!).
-    adc_sync_enable_channel(&adc, ADC_INPUTCTRL_MUXPOS_CTAT_Val);
-    // The channel listed in adc_sync_read_channel is actually ignored(!).
-    // Must be set as above with adc_sync_set_inputs.
-    // Read twice for stability (necessary?)
-    adc_sync_read_channel(&adc, ADC_INPUTCTRL_MUXPOS_CTAT_Val, ((uint8_t*) &ctat), 2);
-    adc_sync_read_channel(&adc, ADC_INPUTCTRL_MUXPOS_CTAT_Val, ((uint8_t*) &ctat), 2);
-    hri_supc_set_VREF_ONDEMAND_bit(SUPC);
+                        IGNORED_CHANNEL);                // channel (ignored)
+
+    adc_sync_read_channel(&adc, IGNORED_CHANNEL, ((uint8_t*) &ctat), 2);
+    adc_sync_read_channel(&adc, IGNORED_CHANNEL, ((uint8_t*) &ctat), 2);
+
+    // Turn off temp sensor.
+    hri_supc_clear_VREF_TSEN_bit(SUPC);
 
     adc_sync_deinit(&adc);
     return calculate_temperature(ptat, ctat);
 #endif // SAMD51
 }
 
+float common_hal_mcu_processor_get_voltage(void) {
+    struct adc_sync_descriptor adc;
+
+    static Adc* adc_insts[] = ADC_INSTS;
+    samd_peripherals_adc_setup(&adc, adc_insts[0]);
+
+#ifdef SAMD21
+    adc_sync_set_reference(&adc, ADC_REFCTRL_REFSEL_INT1V_Val);
+#endif
+
+#ifdef SAMD51
+    hri_supc_set_VREF_SEL_bf(SUPC, SUPC_VREF_SEL_1V0_Val);
+    // ONDEMAND must be clear, and VREFOE must be set, or else the ADC conversion will not complete.
+    // See https://community.atmel.com/forum/samd51-using-intref-adc-voltage-reference
+    hri_supc_clear_VREF_ONDEMAND_bit(SUPC);
+    hri_supc_set_VREF_VREFOE_bit(SUPC);
+    adc_sync_set_reference(&adc, ADC_REFCTRL_REFSEL_INTREF_Val);
+#endif
+
+    adc_sync_set_resolution(&adc, ADC_CTRLB_RESSEL_12BIT_Val);
+    // Channel arg is ignored.
+    adc_sync_set_inputs(&adc,
+                        ADC_INPUTCTRL_MUXPOS_SCALEDIOVCC_Val,     // IOVCC/4 (nominal 3.3V/4)
+                        ADC_INPUTCTRL_MUXNEG_GND_Val,             // neg_input
+                        IGNORED_CHANNEL);                         // channel (ignored).
+    adc_sync_enable_channel(&adc, IGNORED_CHANNEL);
+
+    volatile uint16_t reading;
+
+    // Channel arg is ignored.
+    // Read twice and discard first result, as recommended in section 14 of
+    // http://www.atmel.com/images/Atmel-42645-ADC-Configurations-with-Examples_ApplicationNote_AT11481.pdf
+    // "Discard the first conversion result whenever there is a change in ADC configuration
+    // like voltage reference / ADC channel change"
+    // Empirical observation shows the first reading is quite different than subsequent ones.
+    adc_sync_read_channel(&adc, IGNORED_CHANNEL, ((uint8_t*) &reading), 2);
+    adc_sync_read_channel(&adc, IGNORED_CHANNEL, ((uint8_t*) &reading), 2);
+
+    adc_sync_deinit(&adc);
+    // Multiply by 4 to compensate for SCALEDIOVCC division by 4.
+    return (reading / 4095.0f) * 4.0f;
+}
 
 uint32_t common_hal_mcu_processor_get_frequency(void) {
     // TODO(tannewt): Determine this dynamically.

ports/cxd56/common-hal/microcontroller/Processor.c

@@ -26,14 +26,20 @@
 
 #include <sys/boardctl.h>
 
+// For NAN: remove when not needed.
+#include <math.h>
 #include "py/mphal.h"
 
 uint32_t common_hal_mcu_processor_get_frequency(void) {
     return mp_hal_ticks_cpu();
 }
 
 float common_hal_mcu_processor_get_temperature(void) {
-    return 0;
+    return NAN;
+}
+
+float common_hal_mcu_processor_get_voltage(void) {
+    return NAN;
 }
 
 void common_hal_mcu_processor_get_uid(uint8_t raw_id[]) {

ports/nrf/common-hal/analogio/AnalogIn.c

@@ -29,11 +29,21 @@
 #include "py/runtime.h"
 #include "supervisor/shared/translate.h"
 
-#include "nrfx_saadc.h"
+#include "nrf_saadc.h"
 #include "nrf_gpio.h"
 
 #define CHANNEL_NO 0
 
+void analogin_init(void) {
+    // Calibrate the ADC once, on startup.
+    nrf_saadc_enable();
+    nrf_saadc_event_clear(NRF_SAADC_EVENT_CALIBRATEDONE);
+    nrf_saadc_task_trigger(NRF_SAADC_TASK_CALIBRATEOFFSET);
+    while (nrf_saadc_event_check(NRF_SAADC_EVENT_CALIBRATEDONE) == 0) { }
+    nrf_saadc_event_clear(NRF_SAADC_EVENT_CALIBRATEDONE);
+    nrf_saadc_disable();
+}
+
 void common_hal_analogio_analogin_construct(analogio_analogin_obj_t *self, const mcu_pin_obj_t *pin) {
     if (pin->adc_channel == 0)
         mp_raise_ValueError(translate("Pin does not have ADC capabilities"));

ports/nrf/common-hal/analogio/AnalogIn.h

@@ -36,4 +36,6 @@ typedef struct {
     const mcu_pin_obj_t * pin;
 } analogio_analogin_obj_t;
 
+void analogin_init(void);
+
 #endif // MICROPY_INCLUDED_NRF_COMMON_HAL_ANALOGIO_ANALOGIN_H

ports/nrf/common-hal/microcontroller/Processor.c

@@ -28,6 +28,7 @@
 #include "py/runtime.h"
 #include "supervisor/shared/translate.h"
 
+#include "nrfx_saadc.h"
 #ifdef BLUETOOTH_SD
 #include "nrf_sdm.h"
 #endif
@@ -47,27 +48,73 @@ float common_hal_mcu_processor_get_temperature(void) {
         if (err_code != NRF_SUCCESS) {
             mp_raise_OSError_msg(translate("Cannot get temperature"));
         }
-    }
+        return temp / 4.0f;
+    } // Fall through if SD not enabled.
 #endif
-
     NRF_TEMP->TASKS_START = 1;
-
-    while (NRF_TEMP->EVENTS_DATARDY == 0)
-        ;
-
+    while (NRF_TEMP->EVENTS_DATARDY == 0) { }
     NRF_TEMP->EVENTS_DATARDY = 0;
-
     temp = NRF_TEMP->TEMP;
-
     NRF_TEMP->TASKS_STOP = 1;
-
     return temp / 4.0f;
 }
 
+
+
 uint32_t common_hal_mcu_processor_get_frequency(void) {
     return 64000000ul;
 }
 
+float common_hal_mcu_processor_get_voltage(void) {
+    nrf_saadc_value_t value;
+
+    const nrf_saadc_channel_config_t config = {
+        .resistor_p = NRF_SAADC_RESISTOR_DISABLED,
+        .resistor_n = NRF_SAADC_RESISTOR_DISABLED,
+        .gain = NRF_SAADC_GAIN1_6,
+        .reference = NRF_SAADC_REFERENCE_INTERNAL,
+        .acq_time = NRF_SAADC_ACQTIME_10US,
+        .mode = NRF_SAADC_MODE_SINGLE_ENDED,
+        .burst = NRF_SAADC_BURST_DISABLED,
+        .pin_p = NRF_SAADC_INPUT_VDD,
+        .pin_n = NRF_SAADC_INPUT_VDD,
+    };
+
+    nrf_saadc_resolution_set(NRF_SAADC_RESOLUTION_14BIT);
+    nrf_saadc_oversample_set(NRF_SAADC_OVERSAMPLE_DISABLED);
+    nrf_saadc_enable();
+
+    for (uint32_t i = 0; i < NRF_SAADC_CHANNEL_COUNT; i++) {
+        nrf_saadc_channel_input_set(i, NRF_SAADC_INPUT_DISABLED, NRF_SAADC_INPUT_DISABLED);
+    }
+
+    nrf_saadc_channel_init(0, &config);
+    nrf_saadc_buffer_init(&value, 1);
+
+    nrf_saadc_task_trigger(NRF_SAADC_TASK_START);
+    while (nrf_saadc_event_check(NRF_SAADC_EVENT_STARTED) == 0) { }
+    nrf_saadc_event_clear(NRF_SAADC_EVENT_STARTED);
+
+    nrf_saadc_task_trigger(NRF_SAADC_TASK_SAMPLE);
+    while (nrf_saadc_event_check(NRF_SAADC_EVENT_END) == 0) { }
+    nrf_saadc_event_clear(NRF_SAADC_EVENT_END);
+
+    nrf_saadc_task_trigger(NRF_SAADC_TASK_STOP);
+    while (nrf_saadc_event_check(NRF_SAADC_EVENT_STOPPED) == 0) { }
+    nrf_saadc_event_clear(NRF_SAADC_EVENT_STOPPED);
+
+    nrf_saadc_disable();
+
+    if (value < 0) {
+        value = 0;
+    }
+
+// The ADC reading we expect if VDD is 3.3V.
+#define NOMINAL_VALUE_3_3 (((3.3f/6)/0.6f)*16383)
+    return (value/NOMINAL_VALUE_3_3) * 3.3f;
+}
+
+
 void common_hal_mcu_processor_get_uid(uint8_t raw_id[]) {
     for (int i=0; i<2; i++) {
         ((uint32_t*) raw_id)[i] = NRF_FICR->DEVICEID[i];

ports/nrf/supervisor/port.c

@@ -39,6 +39,7 @@
 #include "shared-module/gamepad/__init__.h"
 #include "common-hal/microcontroller/Pin.h"
 #include "common-hal/_bleio/__init__.h"
+#include "common-hal/analogio/AnalogIn.h"
 #include "common-hal/busio/I2C.h"
 #include "common-hal/busio/SPI.h"
 #include "common-hal/busio/UART.h"
@@ -83,6 +84,10 @@ safe_mode_t port_init(void) {
     // Configure millisecond timer initialization.
     tick_init();
 
+#if CIRCUITPY_ANALOGIO
+    analogin_init();
+#endif
+
     #if CIRCUITPY_RTC
     rtc_init();
     #endif
@@ -102,11 +107,11 @@ void reset_port(void) {
     spi_reset();
     uart_reset();
 
-#ifdef CIRCUITPY_AUDIOBUSIO
+#if CIRCUITPY_AUDIOBUSIO
     i2s_reset();
 #endif
 
-#ifdef CIRCUITPY_AUDIOPWMIO
+#if CIRCUITPY_AUDIOPWMIO
     audiopwmout_reset();
 #endif
 

ports/stm32f4/common-hal/microcontroller/Processor.c

@@ -25,6 +25,7 @@
  * THE SOFTWARE.
  */
 
+#include <math.h>
 #include "common-hal/microcontroller/Processor.h"
 #include "py/runtime.h"
 #include "supervisor/shared/translate.h"
@@ -34,7 +35,11 @@
 #define STM32_UUID ((uint32_t *)0x1FFF7A10)
 
 float common_hal_mcu_processor_get_temperature(void) {
-    return 0;
+    return NAN;
+}
+
+float common_hal_mcu_processor_get_voltage(void) {
+    return NAN;
 }
 
 uint32_t common_hal_mcu_processor_get_frequency(void) {

shared-bindings/microcontroller/Processor.c

@@ -113,10 +113,32 @@ const mp_obj_property_t mcu_processor_uid_obj = {
     },
 };
 
+//|     .. attribute:: voltage
+//|
+//|       The input voltage to the microcontroller, as a float. (read-only)
+//|
+//|       Is `None` if the voltage is not available.
+//|
+STATIC mp_obj_t mcu_processor_get_voltage(mp_obj_t self) {
+    float voltage = common_hal_mcu_processor_get_voltage();
+    return isnan(voltage) ? mp_const_none : mp_obj_new_float(voltage);
+}
+
+MP_DEFINE_CONST_FUN_OBJ_1(mcu_processor_get_voltage_obj, mcu_processor_get_voltage);
+
+const mp_obj_property_t mcu_processor_voltage_obj = {
+    .base.type = &mp_type_property,
+    .proxy = {(mp_obj_t)&mcu_processor_get_voltage_obj,  // getter
+              (mp_obj_t)&mp_const_none_obj,            // no setter
+              (mp_obj_t)&mp_const_none_obj,            // no deleter
+    },
+};
+
 STATIC const mp_rom_map_elem_t mcu_processor_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_frequency), MP_ROM_PTR(&mcu_processor_frequency_obj) },
     { MP_ROM_QSTR(MP_QSTR_temperature), MP_ROM_PTR(&mcu_processor_temperature_obj) },
     { MP_ROM_QSTR(MP_QSTR_uid), MP_ROM_PTR(&mcu_processor_uid_obj) },
+    { MP_ROM_QSTR(MP_QSTR_voltage), MP_ROM_PTR(&mcu_processor_voltage_obj) },
 };
 
 STATIC MP_DEFINE_CONST_DICT(mcu_processor_locals_dict, mcu_processor_locals_dict_table);

shared-bindings/microcontroller/Processor.h

@@ -36,5 +36,6 @@ const mp_obj_type_t mcu_processor_type;
 uint32_t common_hal_mcu_processor_get_frequency(void);
 float common_hal_mcu_processor_get_temperature(void);
 void common_hal_mcu_processor_get_uid(uint8_t raw_id[]);
+float common_hal_mcu_processor_get_voltage(void);
 
 #endif  // MICROPY_INCLUDED_SHARED_BINDINGS_MICROCONTROLLER_PROCESSOR_H