Encoding of b-parasite protocol v2 works I guess

code/nrf-connect/CMakeLists.txt

@@ -13,4 +13,5 @@ target_sources(app PRIVATE
 	src/prst/led.c
 	src/prst/button.c
 	src/prst/ble/ble.c
+	src/prst/ble/encoding.c
 )

code/nrf-connect/src/main.c

@@ -19,10 +19,7 @@ int main(void) {
 
   RET_IF_ERR(prst_led_flash(2));
 
-  RET_IF_ERR(prst_ble_adv_start());
-
   prst_sensors_t sensors;
-
   while (true) {
     RET_IF_ERR(prst_adc_batt_read(&sensors.batt));
     RET_IF_ERR(prst_adc_soil_read(sensors.batt.voltage, &sensors.soil));
@@ -38,6 +35,12 @@ int main(void) {
             (int)sensors.shtc3.temp_c);
     LOG_INF("Humi: %.0f %%", 100.0 * sensors.shtc3.rel_humi);
     LOG_INF("--------------------------------------------------");
-    k_msleep(500);
+
+    RET_IF_ERR(prst_ble_adv_set_data(&sensors));
+    RET_IF_ERR(prst_ble_adv_start());
+
+    k_msleep(5000);
+
+    RET_IF_ERR(prst_ble_adv_stop());
   }
 }

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

@@ -4,12 +4,16 @@
 #include <zephyr/bluetooth/bluetooth.h>
 #include <zephyr/settings/settings.h>
 
+#include "prst/ble/encoding.h"
 #include "prst/macros.h"
 
 LOG_MODULE_REGISTER(ble, LOG_LEVEL_DBG);
 
+static uint8_t service_data[PRST_BLE_ENCODING_SERVICE_DATA_LEN] = {0};
+
 static const struct bt_data ad[] = {
     BT_DATA_BYTES(BT_DATA_FLAGS, (BT_LE_AD_GENERAL | BT_LE_AD_NO_BREDR)),
+    BT_DATA(BT_DATA_SVC_DATA16, service_data, ARRAY_SIZE(service_data)),
     BT_DATA_BYTES(BT_DATA_NAME_COMPLETE, CONFIG_BT_DEVICE_NAME),
 };
 
@@ -17,16 +21,41 @@ static const struct bt_data sd[] = {
     BT_DATA_BYTES(BT_DATA_NAME_COMPLETE, CONFIG_BT_DEVICE_NAME),
 };
 
+// bt_addr_le_t.a holds the MAC address in big-endian.
+static int get_mac_addr(bt_addr_le_t *out) {
+  struct bt_le_oob oob;
+  RET_IF_ERR(bt_le_oob_get_local(BT_ID_DEFAULT, &oob));
+  LOG_HEXDUMP_DBG(oob.addr.a.val, ARRAY_SIZE(oob.addr.a.val),
+                  "Read address using bt_le_oob_get_local");
+  *out = oob.addr;
+
+  // This API doesn't seem to work here.
+  // static bt_addr_le_t addrs[CONFIG_BT_ID_MAX];
+  // static size_t count;
+  // bt_id_get(addrs, &count);
+  // LOG_DBG("[bt_id_get] Received %d addresses", count);
+
+  return 0;
+}
+
 int prst_ble_init() {
   RET_IF_ERR(bt_enable(/*bt_reader_cb_t=*/NULL));
   if (IS_ENABLED(CONFIG_SETTINGS)) {
     RET_IF_ERR_MSG(settings_load(), "Error in settings_load()");
   }
+
+  struct bt_le_oob oob;
+  RET_IF_ERR(bt_le_oob_get_local(BT_ID_DEFAULT, &oob));
+  LOG_INF("ADDR: ");
+  LOG_HEXDUMP_INF(oob.addr.a.val, 6, ":");
   return 0;
 }
 
 int prst_ble_adv_start() {
-  return bt_le_adv_start(BT_LE_ADV_CONN, ad, ARRAY_SIZE(ad), sd,
+  // If BT_LE_ADV_NCONN_IDENTITY, this function will advertise with a static MAC
+  // address programmed in the chip. If BT_LE_ADV_NCONN, this function returns
+  // advertises with a random MAC each time.
+  return bt_le_adv_start(BT_LE_ADV_NCONN_IDENTITY, ad, ARRAY_SIZE(ad), sd,
                          ARRAY_SIZE(sd));
 }
 
@@ -35,5 +64,9 @@ int prst_ble_adv_stop() {
 }
 
 int prst_ble_adv_set_data(const prst_sensors_t *sensors) {
-  return 0;
+  bt_addr_le_t addr;
+  RET_IF_ERR(get_mac_addr(&addr));
+  LOG_HEXDUMP_WRN(addr.a.val, ARRAY_SIZE(addr.a.val), "GOT ADDR: ");
+  return prst_ble_encode_service_data(sensors, &addr, service_data,
+                                      sizeof(service_data));
 }

code/nrf-connect/src/prst/ble/encoding.c

@@ -0,0 +1,54 @@
+#include "prst/ble/encoding.h"
+
+#include <logging/log.h>
+
+#include "prst/macros.h"
+
+LOG_MODULE_DECLARE(ble, LOG_LEVEL_DBG);
+
+int prst_ble_encode_service_data(const prst_sensors_t* sensors,
+                                 const bt_addr_le_t* bt_addr, uint8_t* out,
+                                 uint8_t out_len) {
+  RET_CHECK(out_len >= PRST_BLE_ENCODING_SERVICE_DATA_LEN,
+            "Buffer is not large enough");
+
+  // 0x181c - BTHome Service UUID.
+  out[0] = 0x1c;
+  out[1] = 0x18;
+
+  // Soil Moisture.
+  //
+  // Four bits for the protocol version.
+  out[2] |= (2 << 4) & 0xf0;
+
+  // Bit 0 of byte 0 specifies whether or not ambient light data exists in the
+  // payload.
+  out[2] |= 1;
+
+  // 4 bits for a small wrap-around counter for deduplicating messages on the
+  // receiver.
+  // out[3] = sensors->run_counter & 0x0f;
+
+  out[4] = sensors->batt.millivolts >> 8;
+  out[5] = sensors->batt.millivolts & 0xff;
+
+  int16_t temp_centicelsius = 100 * sensors->shtc3.temp_c;
+  out[6] = temp_centicelsius >> 8;
+  out[7] = temp_centicelsius & 0xff;
+
+  uint16_t humi = sensors->shtc3.rel_humi * UINT16_MAX;
+  out[8] = humi >> 8;
+  out[9] = humi & 0xff;
+
+  uint16_t soil_moisture = sensors->soil.percentage * UINT16_MAX;
+  out[10] = soil_moisture >> 8;
+  out[11] = soil_moisture & 0xff;
+
+  // MAC address in big-endian.
+  memcpy(out + 12, bt_addr->a.val, BT_ADDR_SIZE);
+
+  out[18] = sensors->photo.brightness >> 8;
+  out[19] = sensors->photo.brightness & 0xff;
+
+  return 0;
+}

code/nrf-connect/src/prst/ble/encoding.h

@@ -1,3 +1,14 @@
 #ifndef _PRST_BLE_ENCODING_H_
 #define _PRST_BLE_ENCODING_H_
+
+#include <zephyr/bluetooth/bluetooth.h>
+
+#include "prst/data.h"
+
+#define PRST_BLE_ENCODING_SERVICE_DATA_LEN 20
+
+int prst_ble_encode_service_data(const prst_sensors_t* sensors,
+                                 const bt_addr_le_t* bt_addr, uint8_t* out,
+                                 uint8_t out_len);
+
 #endif  // _PRST_BLE_ENCODING_H_

code/nrf-connect/src/prst/macros.h

@@ -16,4 +16,7 @@
 
 #define RET_IF_ERR(expr) RET_IF_ERR_MSG(expr, "")
 
+// Checks that expr evaluates to true, otherwise return 1.
+#define RET_CHECK(expr, msg) RET_IF_ERR_MSG(!(expr), msg)
+
 #endif  // _PRST_MACROS_H_