Extracts BLE internals to a BLEAdvertising class

README.md

@@ -2,8 +2,9 @@
 A low power soil moisture sensor based on the nRF52840.
 
 # TODO
-* Implement BLE advertising with moisture, battery level
+* Implement battery level monitoring
 * Figure out how to calibrate the ADC when running from different voltages, as the battery discharges
+* Experiment with different TX power / battery tradeoff. Since we'll be deepsleeping most of the time, maybe we can get away with a lot of TX power.
 * Implement deep sleep
 * Measure current in deep sleep
 * Measure current in operation (ADC + BLE adversiting)
@@ -15,6 +16,7 @@ A low power soil moisture sensor based on the nRF52840.
 * Design new board using the nrf52 instead of esp32
 
 # Done
+* Implement BLE advertising with moisture
 * Implement ADC for the parasitic capacitor; check out air/water range (using protoboard)
 * Simple PWM square wave generator
 * Hook square wave generator to the protoboard sensor circuit

code/parasite/lib/parasite/parasite/ble.cpp

@@ -1 +1,46 @@
 #include "ble.h"
+
+#include <bluefruit.h>
+
+namespace parasite {
+namespace {}
+
+void BLEAdvertiser::SetData(BLEAdvertisementData data) {
+  data_ = std::move(data);
+  if (is_running_) {
+    Bluefruit.Advertising.stop();
+  }
+  Bluefruit.Advertising.clearData();
+  Bluefruit.Advertising.setData(data_.GetRawData(), data_.GetDataLen());
+  if (is_running_) {
+    Bluefruit.Advertising.start(0);
+  }
+}
+
+void BLEAdvertiser::Init() {
+  ble_gap_addr_t addr;
+  addr.addr_id_peer = 1;
+  addr.addr_type = BLE_GAP_ADDR_TYPE_PUBLIC;
+  std::copy(std::begin(mac_addr_), std::end(mac_addr_), std::begin(addr.addr));
+  Bluefruit.begin(1, 1);
+  Bluefruit.setName("Parasite");
+  Bluefruit.setAddr(&addr);
+  is_initialized_ = true;
+}
+
+void BLEAdvertiser::Start() {
+  if (!is_initialized_) {
+    Init();
+  }
+  Bluefruit.Advertising.setInterval(32, 244);  // in unit of 0.625 ms
+  Bluefruit.Advertising.setFastTimeout(30);    // number of seconds in fast mode
+  Bluefruit.Advertising.start(0);  // 0 = Don't stop advertising after n seconds
+  is_running_ = true;
+}
+
+void BLEAdvertiser::Stop() {
+  Bluefruit.Advertising.stop();
+  is_running_ = false;
+}
+
+}  // namespace parasite

code/parasite/lib/parasite/parasite/ble.h

@@ -1,13 +1,29 @@
 #ifndef _PARASITE_BLE_H_
 #define _PARASITE_BLE_H_
 
+#include <array>
 #include <string>
 
+#include "parasite/ble_advertisement_data.h"
+
 namespace parasite {
 
+using MACAddr = std::array<uint8_t, 6>;
+
 class BLEAdvertiser {
  public:
-  void Advertise(std::string name, double moisture) {}
+  explicit BLEAdvertiser(MACAddr mac_addr) : mac_addr_(std::move(mac_addr)) {}
+  void SetData(BLEAdvertisementData data);
+  void Start();
+  void Stop();
+  bool IsRunning() const { return is_running_; };
+
+ private:
+  bool is_initialized_;
+  bool is_running_;
+  void Init();
+  BLEAdvertisementData data_;
+  MACAddr mac_addr_;
 };
 
 }  // namespace parasite

code/parasite/lib/parasite/parasite/ble_advertisement_data.cpp

@@ -8,4 +8,4 @@ void BLEAdvertisementData::SetRawSoilMoisture(int raw_soil_moisture) {
   data_[kRawSoilMoistureOffset + 1] = packed_value & 0xff;
 }
 
-}
+}  // namespace parasite

code/parasite/src/main.cpp

@@ -1,7 +1,7 @@
 #include <Arduino.h>
-#include <bluefruit.h>
 
 #include <cstring>
+#include <vector>
 
 #include "parasite/ble.h"
 #include "parasite/ble_advertisement_data.h"
@@ -14,53 +14,44 @@ constexpr int kSensAnalogPin = 4;  // AIN2
 constexpr int kDischargeEnablePin = 16;
 constexpr double kPWMFrequency = 500000;
 
-ble_gap_addr_t kGAPAddr{
-    1,
-    BLE_GAP_ADDR_TYPE_PUBLIC,
-    // This is the "reverse" order in comparison that the colon-separated
-    // human-readable MAC addresses.
-    {0x01, 0x02, 0x03, 0x04, 0x05, 0x06},
-};
+const parasite::MACAddr kMACAddr = {0x01, 0x02, 0x03, 0x04, 0x05, 0x06};
+parasite::BLEAdvertiser advertiser(kMACAddr);
 
-void setupAdvertising() {
-  Bluefruit.begin(1, 1);
-  Bluefruit.setName("Parasite");
-  Bluefruit.setAddr(&kGAPAddr);
-}
-
-void updateAdvertisingData(int moisture_level) {
+void updateAdvertisingData(parasite::BLEAdvertiser *advertiser,
+                           int moisture_level) {
   parasite::BLEAdvertisementData data;
   data.SetRawSoilMoisture(moisture_level);
-  Bluefruit.Advertising.stop();
-  Bluefruit.Advertising.clearData();
-  Bluefruit.Advertising.setData(data.GetRawData(), data.GetDataLen());
-  Bluefruit.Advertising.setInterval(32, 244);  // in unit of 0.625 ms
-  Bluefruit.Advertising.setFastTimeout(30);    // number of seconds in fast mode
-  Bluefruit.Advertising.start(0);  // 0 = Don't stop advertising after n seconds
+
+  advertiser->SetData(data);
+
+  if (!advertiser->IsRunning()) {
+    advertiser->Start();
+  }
 }
 
 void setup() {
   Serial.begin(9600);
+
   pinMode(kLED1Pin, OUTPUT);
   pinMode(kDischargeEnablePin, OUTPUT);
+
+  // Activate the PWM signal.
   parasite::SetupSquareWave(kPWMFrequency, kPWMPin);
+
+  // Enable fast discharge cycle.
   digitalWrite(kDischargeEnablePin, HIGH);
 
+  // We setup the analog reference to be VDD. This allows us to cancel out
+  // the effect of the battery discharge across time, since the RC circuit
+  // also depends linearly on VDD.
+  // TODO(rbaron): empirically prove/disprove this.
   analogReference(AR_VDD4);
-
-  setupAdvertising();
-
-  Serial.println("Will advertise with MAC:");
-  for (const auto byte : kGAPAddr.addr) {
-    Serial.printf("0x%02x ", byte);
-  }
-  Serial.println();
 }
 
 void loop() {
   int sens_val = analogRead(kSensAnalogPin);
   Serial.printf("Val: %d\n", sens_val);
   digitalToggle(kLED1Pin);
-  updateAdvertisingData(sens_val);
+  updateAdvertisingData(&advertiser, sens_val);
   delay(500);
 }