BLE sample kinda works. Pending calibration

code/nrf-connect/Kconfig

@@ -14,10 +14,18 @@ config PRST_NETWORK_BLE
 
 endchoice  # PRST_NETWORK
 
+config PRST_SLEEP_DURATION_SEC
+	int "Sleep duration in seconds"
+	default 1
+
 ###
 ### BLE configs
 ###
 
+config PRST_BLE_ADV_DURATION_SEC
+	int "Advertising duration in seconds"
+	default 1
+
 choice PRST_BLE_ENCODING
 	prompt "b-parasite BLE encoding"
 	depends on PRST_NETWORK_BLE

code/nrf-connect/boards/arm/bparasite_nrf52840/bparasite_nrf52840.dts

@@ -35,8 +35,8 @@
 
 	soil_pwm: soil_pwm {
 		compatible = "pwm-fixed";
-		pwms = <&pwm0 0 PWM_MSEC(100) PWM_POLARITY_NORMAL>;
-		pulse = <PWM_MSEC(50)>;
+		pwms = <&pwm0 0 PWM_USEC(2) PWM_POLARITY_NORMAL>;
+		pulse = <PWM_USEC(1)>;
 	};
 
 	ctrl {
@@ -95,10 +95,12 @@
 	#address-cells = <1>;
 	#size-cells = <0>;
 	status = "ok";
+
+	// Soil.
 	channel@0 {
 		reg = <0>;
 		zephyr,gain = "ADC_GAIN_1_6";
-		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,reference = "ADC_REF_VDD_1_4";
 		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
 		// P0.03.
 		zephyr,input-positive = <NRF_SAADC_AIN1>;
@@ -106,6 +108,7 @@
 
 	};
 
+	// Photo.
 	channel@1 {
 		reg = <1>;
 		zephyr,gain = "ADC_GAIN_1_6";
@@ -116,6 +119,7 @@
 		zephyr,resolution = <10>;
 	};
 
+	// Battery.
 	channel@2 {
 		reg = <2>;
 		zephyr,gain = "ADC_GAIN_1_6";

code/nrf-connect/src/main.c

@@ -41,16 +41,12 @@ int main(void) {
     RET_IF_ERR(prst_ble_adv_set_data(&sensors));
     RET_IF_ERR(prst_ble_adv_start());
 
-    k_sleep(K_SECONDS(2));
+    k_sleep(K_SECONDS(CONFIG_PRST_BLE_ADV_DURATION_SEC));
+    k_msleep(200);
+    k_busy_wait(200 * 1000);
 
     RET_IF_ERR(prst_ble_adv_stop());
 
-    k_sleep(K_SECONDS(2));
-
-    prst_led_flash(1);
-
-    // Example: go to deep sleep.
-    pm_state_force(0u, &(struct pm_state_info){PM_STATE_SOFT_OFF, 0, 0});
-    k_sleep(K_SECONDS(2));
+    k_sleep(K_SECONDS(CONFIG_PRST_SLEEP_DURATION_SEC));
   }
 }

code/nrf-connect/src/prst/adc.c

@@ -1,19 +1,23 @@
 #include "adc.h"
 
 #include <drivers/adc.h>
+#include <drivers/gpio.h>
 #include <drivers/pwm.h>
 #include <logging/log.h>
 #include <zephyr/zephyr.h>
 
 #include "macros.h"
 
-LOG_MODULE_REGISTER(adc, LOG_LEVEL_WRN);
+LOG_MODULE_REGISTER(adc, LOG_LEVEL_DBG);
 
 // PWM spec for square wave. Input to the soil sensing circuit.
 static const struct pwm_dt_spec soil_pwm_dt =
     PWM_DT_SPEC_GET(DT_NODELABEL(soil_pwm));
 static const uint32_t pulse = DT_PROP(DT_NODELABEL(soil_pwm), pulse);
 
+struct gpio_dt_spec fast_disch_dt =
+    GPIO_DT_SPEC_GET(DT_NODELABEL(fast_disch), gpios);
+
 // Shared buffer and adc_sequennce.
 static int16_t buf;
 static struct adc_sequence sequence = {
@@ -36,8 +40,8 @@ static inline float get_soil_moisture_percent(float battery_voltage,
   const double x = battery_voltage;
   const double dry = -12.9 * x * x + 111 * x + 228;
   const double wet = -5.71 * x * x + 60.2 * x + 126;
-  LOG_DBG("Batt: %.2f", x);
-  LOG_DBG("Dry: %.2f | wet: %.2f", dry, wet);
+  LOG_DBG("Raw %u | Batt: %.2f | Dry: %.2f | Wet: %.2f", raw_adc_output, x, dry,
+          wet);
   return (raw_adc_output - dry) / (wet - dry);
 }
 
@@ -64,6 +68,9 @@ int prst_adc_init() {
   for (int i = 0; i < sizeof(all_specs) / sizeof(all_specs[0]); i++) {
     RET_IF_ERR(adc_channel_setup_dt(all_specs[i]));
   }
+
+  RET_IF_ERR(!device_is_ready(fast_disch_dt.port));
+  return gpio_pin_configure_dt(&fast_disch_dt, GPIO_OUTPUT);
   return 0;
 }
 
@@ -73,6 +80,9 @@ int prst_adc_batt_read(prst_adc_read_t* out) {
 }
 
 int prst_adc_soil_read(float battery_voltage, prst_adc_soil_moisture_t* out) {
+  // Enable fast discharge circuit.
+  RET_IF_ERR(gpio_pin_set_dt(&fast_disch_dt, 1));
+
   // Start PWM.
   RET_IF_ERR(pwm_set_dt(&soil_pwm_dt, soil_pwm_dt.period, pulse));
 
@@ -83,6 +93,9 @@ int prst_adc_soil_read(float battery_voltage, prst_adc_soil_moisture_t* out) {
   // Stop PWM.
   RET_IF_ERR(pwm_set_dt(&soil_pwm_dt, 0, 0));
 
+  // Turn off fast discharge circuit.
+  RET_IF_ERR(gpio_pin_set_dt(&fast_disch_dt, 0));
+
   out->percentage = get_soil_moisture_percent(battery_voltage, buf);
   return 0;
 }