Harald's Random Stuff

Bluetooth and its LE variant are new areas for me and, but the learning curve is not too steep thanks to Puck.js. Making  it do what I want is not easy though since I don’t know what it can do.

The most important documents are:

• https://www.bluetooth.com/specifications/gatt/services for the GATT services which are known
• https://www.bluetooth.com/specifications/gatt/characteristics for the Characteristics of those
• The Espruino Puck.js forum in case you have questions
• The Espruino source code and
• The reference information for Espruino hardware and software (see the Bluetooth and NRF functions and their examples)

Here an example:

// Have a service to show temperature and battery level
// This is only visible when you are connecting to the Puck

var currentTemperature=E.getTemperature().toFixed(2)*100;

console.log("Temp: "+currentTemperature);

NRF.setServices({
 0x1809 : { // Health Thermometer
  0x2A6E: { // Temperature
   readable: true,
   notify: true,
   value : [ currentTemperature % 256, currentTemperature / 256 ]
  }
 },
 0x180f : { // Battery Level
  0x2a19 : { // Percentage
   readable : true,
   notify: true,
   value: [ Puck.getBatteryPercentage() ],
  }
 }
});

// Updating the temperature

setInterval(function() {
 currentTemperature += 1; // For debugging: increase temp by 0.01 degree per update
 NRF.updateServices({
  0x1809 : {
   0x2A6E : {
    value : [ currentTemperature % 256, currentTemperature / 256 ],
    notify: true
   }
  }
 });
}, 2000);

Small Sunday afternoon project: Make the ESP8266 with Espruino work with the OLED display I have. NodeMCU has no issues. Time to try Espruino+JavaScript instead of NodeMCU+Lua.

Ingredients:

• Firmware image from https://github.com/MaBecker/esp8266/tree/master/firmware/espruino_1v91.2150_esp8266 as this one does have the Graphics library installed (see the Espruino forum here) where the default one does not.
• Flash via

~/.local/bin/esptool.py --port /dev/ttyUSB0 --baud 115200 write_flash 
--flash_freq 80m --flash_mode qio --flash_size 32m \
 0x0000 "boot_v1.6.bin" \
0x1000 espruino_esp8266_user1.bin \
0x3FC000 esp_init_data_default.bin \
0x37E000 blank.bin

• and then this little program will use it (if you have configured everything correctly and I2C works as it should):

I2C1.setup({sda: NodeMCU.D2, scl: NodeMCU.D1});

function start(){
 // write some text
 g.drawString("Hello World!",2,2);
 // write to the screen
 g.flip(); 
}

var g = require("SSD1306").connect(I2C1, start, {height:64});

Took me some tries to get it working and very helpful was the ability to scan the I2C bus:

function isDeviceOnBus(i2c,id) {
  try {
    return i2c.readFrom(id,1);
  }
  catch(err) {
    return -1;
  }
}

function detect(i2c,first, last) {
  first = first | 0;
  last = last | 0x77;
  var idsOnBus = Array();
  for (var id = first; id <= last; id++) {
    if ( isDeviceOnBus(i2c,id) != -1) {
      idsOnBus.push("0x"+id.toString(16));
    }
  }
  return idsOnBus;
}

I2C1.setup({sda: NodeMCU.D2, scl: NodeMCU.D1});
console.log('I2C detect as array:',detect(I2C1));

Note that I could not make the Wemos OLED work as its size (64×48) seems not supported. The 128×64 display I have worked out of the box. 128×32 is supposed to work too (see here).