polymachine/b-parasite-esp32
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Uses service data instead of manufacturer specific data for advertising sensor values

Browse source
This commit is contained in:
rbaron 2021-02-13 11:48:56 +01:00
parent 02e2f3d074
commit df97f89bd9
2 changed files with 37 additions and 14 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

42
code/parasite/src/main.cpp
View file

@ -13,17 +13,26 @@ constexpr int kSensAnalogPin = 4; // AIN2
constexpr int kDischargeEnablePin = 16;
constexpr double kPWMFrequency = 500000;
char manufacturer_data[] = {
0x01,
0x02,
0x03,
};
constexpr int kManufacturerDataLen = 3;
// We can have at most 31 bytes here.
uint8_t advertisement_data[] = {
9, // Length of name.
BLE_GAP_AD_TYPE_COMPLETE_LOCAL_NAME,
'P', 'a', 'r', 'a', 's', 'i', 't', 'e',
7, // Length of the service data.
BLE_GAP_AD_TYPE_SERVICE_DATA,
0x1a, 0x18, // Environment sensor service UUID.
0x00, 0x00, // Raw soil humidity.
0x00, 0x00, // Percentage soil humidity.
};
constexpr size_t kRawSoilMoistureOffset = 14;
constexpr size_t kPercentSoilMoistureOffset = kRawSoilMoistureOffset + 2;
constexpr size_t kTemperatureOfsset = kRawSoilMoistureOffset + 4;
ble_gap_addr_t kGAPAddr{
1,
BLE_GAP_ADDR_TYPE_RANDOM_STATIC,
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},
@ -36,13 +45,16 @@ void setupAdvertising() {
}
void updateAdvertisingData(int moisture_level) {
manufacturer_data[2] = moisture_level & 0xff;
manufacturer_data[1] = 0xff;
uint16_t packed_raw_moisture = moisture_level;
advertisement_data[kRawSoilMoistureOffset] = packed_raw_moisture >> 1;
advertisement_data[kRawSoilMoistureOffset + 1] = packed_raw_moisture & 0xff;
// manufacturer_data[1] = 0xff;
Bluefruit.Advertising.stop();
Bluefruit.Advertising.clearData();
Bluefruit.Advertising.addName();
Bluefruit.Advertising.addManufacturerData(manufacturer_data,
kManufacturerDataLen);
// Bluefruit.Advertising.addName();
// Bluefruit.Advertising.addManufacturerData(manufacturer_data,
// kManufacturerDataLen);
Bluefruit.Advertising.setData(advertisement_data, sizeof(advertisement_data));
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
@ -58,6 +70,12 @@ void setup() {
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() {

9
resources.md
View file

@ -151,6 +151,11 @@ I'm getting ~680 when in the air; ~65 while holding the sensor. The default reso
* [main_loop](https://github.com/atc1441/ATC_MiThermometer/blob/916cef7db24977ec187e68ab6e718b7b7a4988e6/ATC_Thermometer/app.c#L76)
* [advertisement_data](https://github.com/atc1441/ATC_MiThermometer/blob/master/ATC_Thermometer/ble.c#L39) definition
* [set_adv_data](https://github.com/atc1441/ATC_MiThermometer/blob/master/ATC_Thermometer/ble.c#L178) - where the temp, humidity and batt levels are encoded into the advertisement data
* They don't use manufacturer data. They use a custom UUID service (0x181a).
* Using the manufacturer data requires a SIG membership for getting the manufacturer ID (first two bytes in the manufacturer data)
* Using the service data also requires applying for a 16-bit (2 byte) ID from SIG ([link](https://www.bluetooth.com/specifications/assigned-numbers/))
* Aha! I think we can use the 0x181a service UUID (the same one the alternative xiaomi firmware uses). This service is reserved for "Environmental Sensors". Check out the offical assigned numbers list [here](https://btprodspecificationrefs.blob.core.windows.net/assigned-values/16-bit%20UUID%20Numbers%20Document.pdf).
* We can use the SERVICE_DATA (int 16) in the BLE advertisement packet to pack service data for the UUID 0x181a.
* How the xiaomi BLE temp sensor works in ESPHome: [link](https://github.com/esphome/esphome/blob/5c86f332b269fd3e4bffcbdf3359a021419effdd/esphome/components/xiaomi_lywsd03mmc/xiaomi_lywsd03mmc.cpp)
* [How advertisement works YouTube video](https://www.youtube.com/watch?v=CJcLabp42b4) by nordic
* In your case:
@ -176,8 +181,8 @@ I'm getting ~680 when in the air; ~65 while holding the sensor. The default reso
* Can we update the manufaturer advertising data dynamically?
* [Hint on devzone.nordicsemi.com](https://devzone.nordicsemi.com/f/nordic-q-a/11217/adc-values-in-advertising-data-dynamically-changing)
* What MAC address to use?
* Public
* Random
* Public - might have some security implications, since BLE can be used for tracking
* Random - safer, since its random, but it "breaks" our MAC-addr based Hub config
## Packing values into the advertising packet
### Soil humidity