Non blocking miThermometer.getData()

[Art-ut-Kia]

Hi, very happy to have found this library. I'd like to integrate several Mijia temp sensors in a home monitoring system.

Is your feature request related to a problem? Please describe.
The example (ESP32_ATC_MiThermometer_Client.ino) works well. However the miThermometer.getData() is blocking.
It's not a good news to have the ESP32 blocked for 5 seconds and not reacting to the user inputs

Describe the solution you'd like
A callback mechanism, integrated in the ATC_MiThermometer class, that would manage the sensor callbacks

• semaphores to know whether new data is available or not

Describe alternatives you've considered
Make use of FreeRtos to launch getData in a seperate task. But I'm not sure it's compatible with NimBLEDevice.h/.cpp

Additional context
Ideally my system would include a touchscreen and implement a thermostat feature.
Blocking that for 5s is not acceptable

[matthias-bs]

This makes sense! It may take a while until I find some spare time to work on it, though!

In any case, I recommend to use https://github.com/matthias-bs/ATC_MiThermometer instead of this repository.

[matthias-bs]

Did you have a look at this?
https://github.com/theengs/decoder/blob/development/examples/ESP32/ScanAndDecode/ScanAndDecode.ino

It seems to be possible to set a "scan end callback".

[Art-ut-Kia]

Thanx for your answers.
Meanwhile, I gave a try to FreeRTOS. I plugged it in your example from "https://github.com/matthias-bs/ATC_MiThermometer".
After tarnsferring all the code from loop() function into a FreeRTOS task, it worked fine and let the loop() function free for doing any required itterative stuff.
Thanx again for your job.

[matthias-bs]

Oh, that's good news! Would you mind providing your code as an example?

You can either fork the repository and make a pull request or attach your code to this issue and I will try to integrate it.

[Art-ut-Kia]

// https://github.com/matthias-bs/ATC_MiThermometer
// Mijia lywsd03mmc thermometers are first to be loaded with a custom firmware as per:
// https://pvvx.github.io/ATC_MiThermometer/TelinkMiFlasher.html

#include <FreeRTOS/FreeRTOS.h>
#include "ATC_MiThermometer.h"

// List of known sensors' BLE addresses
std::vector<std::string> knownBLEAddresses = {"a4:c1:38:02:8B:E0", "a4:c1:38:64:8F:10", "a4:c1:38:F3:C1:B4"};
ATC_MiThermometer miTh(knownBLEAddresses);

void setup() {
  pinMode(LED_BUILTIN, OUTPUT); digitalWrite(LED_BUILTIN, LOW);
  Serial.begin(115200);
  miTh.begin(); // initialization of Mijia sensors acquisition
  xTaskCreate(miThTask     ,   "miThTask",      10000,  NULL,        1,   NULL); // stack size: tried 1000, not sufficient
  //          task function, name of task, stack size, param, priority, handle
}

void loop() {
  digitalWrite(LED_BUILTIN, LOW);
  vTaskDelay(500 / portTICK_PERIOD_MS);
  digitalWrite(LED_BUILTIN, HIGH);
  vTaskDelay(500 / portTICK_PERIOD_MS);
}

void miThTask(void *pvParameters) {
  while (1) {
    miTh.resetData(); // Set sensor data invalid
    unsigned count = miTh.getData(5); // get sensor data (run BLE scan for 5 seconds)
    Serial.println("BLE Devices found (total): " + String(count));
    for (int i=0; i < miTh.data.size(); i++) {  
      if (miTh.data[i].valid) {
        MiThData_S* pMTD = &miTh.data[i]; // Mijia thermometer data pointer
        Serial.printf("sensor #: %d ; ", i);
        Serial.printf("temperature: %.2f°C ; ", pMTD->temperature *0.01f );
        Serial.printf("humidity: %.2f%% ; ",    pMTD->humidity    *0.01f );
        Serial.printf("voltage: %.3fV ; ",      pMTD->batt_voltage*0.001f);
        Serial.printf("battery charge: %d%% ; ",pMTD->batt_level);
        Serial.printf("RF power: %ddBm\n",      pMTD->rssi);
      }
    }
    miTh.clearScanResults(); // clear results from BLEScan buffer to release memory
    Serial.println();
    vTaskDelay(1000 / portTICK_PERIOD_MS);
  }
}

[Art-ut-Kia]

I have a github account, but I'm not fluent at all with forks and pull requests.
So I let you integrate it.
To complete that and make the code usable, I will implement MutEx mechanisms to pass the sensors readings to other tasks (e.g. to the loop() function) rather than printing it on serial monitor.
I will also share the relevant code.

[matthias-bs]

Thank you very much in advance!

[Art-ut-Kia]

A little bit complicated, with a lot of data copies.
But it's the price to pay to render the sensors acquisition non blocking.
Still missing a semaphore mechanism to indicate that data were refreshed

// non-blocing Mijia lywsd03mmc thermometers acquisition
// based on this library:
// https://github.com/matthias-bs/ATC_MiThermometer
// Mijia lywsd03mmc thermometers are first to be loaded with a custom firmware as per:
// https://pvvx.github.io/ATC_MiThermometer/TelinkMiFlasher.html

#include "ATC_MiThermometer.h"

// List of known sensors' BLE addresses
std::vector<std::string> knownBLEAddresses = {"a4:c1:38:02:8B:E0", "a4:c1:38:64:8F:10", "a4:c1:38:F3:C1:B4"};
ATC_MiThermometer miTh(knownBLEAddresses);

MiThData_S miThData[3];
SemaphoreHandle_t mutex[3];

void setup() {
  Serial.begin(115200);
  for (int i=0; i<3; i++) mutex[i] = xSemaphoreCreateMutex();
  miTh.begin(); // initialization of Mijia sensors acquisition
  xTaskCreate(miThReadingTask,   "miThTask",      10000,  NULL,        1,   NULL); // stack size: tried 1000, not sufficient
  //            task function, name of task, stack size, param, priority, handle
}

void loop() {
  int count = 0;
  for (int i=0; i < 3; i++) {

    // gets a local copy of the ith sensor reading
    // mutex protection ensures reading struct integrity
    MiThData_S miThDat;
    if (xSemaphoreTake(mutex[i], (TickType_t)10)==pdTRUE) {
      miThDat = miThData[i];
      xSemaphoreGive(mutex[i]);
    } else miThDat.valid = false;

    // displays sensor # and sensor reading if valid
    if (miThDat.valid) {
      count++;
      Serial.printf("sensor #%d -> ", i);
      Serial.printf("temperature: %.2fC ; ",   miThDat.temperature *0.01f );
      Serial.printf("humidity: %.2f%% ; ",     miThDat.humidity    *0.01f );
      Serial.printf("voltage: %.3fV ; ",       miThDat.batt_voltage*0.001f);
      Serial.printf("battery charge: %d%% ; ", miThDat.batt_level);
      Serial.printf("RF power: %ddBm\n",       miThDat.rssi);
    }
  }
  if (count) Serial.println();
  vTaskDelay(6000 / portTICK_PERIOD_MS);
}

void miThReadingTask(void *pvParameters) {
  while (1) {
    miTh.resetData(); // Set sensor data invalid
    miTh.getData(5); // get sensor data (run BLE scan for 5 seconds)
    // makes a copy of each sensor reading under mutex protection
    for (int i=0; i < 3; i++) if (xSemaphoreTake(mutex[i], (TickType_t)10)==pdTRUE) {
      miThData[i] = miTh.data[i];
      xSemaphoreGive(mutex[i]);
    } else miThData[i].valid = false;
    miTh.clearScanResults(); // clear results from BLEScan buffer to release memory
    vTaskDelay(1000 / portTICK_PERIOD_MS);
  }
}

[matthias-bs]

Hi,

thank you very much! I added it to the examples directory.

The CI run (see https://github.com/matthias-bs/ATC_MiThermometer/actions) gives me a compile error due to FreeRTOS missing:

Building ATC_MiThermometer_Nonblocking.ino ... 
/home/runner/work/ATC_MiThermometer/ATC_MiThermometer/examples/ATC_MiThermometer_Nonblocking/ATC_MiThermometer_Nonblocking.ino:9:10: fatal error: FreeRTOS/FreeRTOS.h: No such file or directory
 #include <FreeRTOS/FreeRTOS.h>
          ^~~~~~~~~~~~~~~~~~~~~
compilation terminated. 

Where can I find it to include it in the build run?

Thanks in advance!

Matthias

[matthias-bs]

O.k., it works if I comment out this #include directive.
Seems to be part of the Arduino-ESP32 environment.

I also had to add the following for the generic esp32:esp32:esp32 target:

#ifndef LED_BUILTIN
#define LED_BUILTIN 13
#endif

Which target have you been using?

[matthias-bs]

Please let me know when you think you have a stable version; I will create a new release then.

[Art-ut-Kia]

The FreeRTOS library can be downloaded from Arduino IDE as can be seen in the following screenshot