OLED + Electric Imp = <3

After reading this post http://www.smovs.dk/blog/2014/03/03/electric-imp-driving-a-small-oled-display/ I decided to try those displays myself too, and oh my do I like them!

eBay: http://www.ebay.co.uk/itm/1-3-Serial-UART-I2C-SPI-128×64-OLED-LED-LCD-Display-Module-Blue-for-Arduino-/371010833249

To control the display you only need 3 wires. Power, GND and TX, so on the Imp it only takes up one pin.

My first try to just make it show something, was pretty much the same as on the blog post mentioned before. All it does is to tell the ssid it is connected to, and the signal strength.

2014-04-09 21.35.05-1

While making the bar graph I also learnt more about how to make white and black textures, so it is possible to first draw something, then put black over it to turn parts of it off again. In the bar I use this, because the bar is actually two rectangles, one white and one black, just behind it to make sure the bar can both go up and down again.

To make the display show this, I used this code

display <- hardware.uart12;
display.configure(9600, 8, PARITY_NONE, 1, NO_RX);

display.write("CL"); display.write(0x01); //Clear display

display.write("SF"); display.write(0); display.write(0x01); //Set font 6,10,18,51,120,123,0

display.write("CS0"); display.write(0x01); //Cursor off

display.write("SC1"); display.write(0x01); //Set graphics to white

display.write("TP"); display.write(0); display.write(0); display.write(0x01); //Move to collum 0 row 0
display.write("TT" + "SSID: " + imp.getssid()); display.write(0x00); // Write text

display.write("TP"); display.write(2); display.write(1); //Move to collum 2 row 1
display.write("TT" + "dB: "); display.write(0x00); // Write text

function progressBar(barX, barY, barHeight, barWidth, border, percentage)
  barSplit <- ((((barWidth-2)-(border*2))/100.0)*percentage).tointeger();

  display.write("SC1"); display.write(0x01);
  display.write("DR"); display.write(barX); display.write(barY); display.write(barX + barWidth); display.write(barY + barHeight); display.write(0x01);

  if (barSplit > 0)
    display.write("FR"); display.write(barX+border+1); display.write(barY+border+1); display.write(barX+1+border+barSplit); display.write(barY+1+border + barHeight-2-(border*2)); display.write(0x01);
  if (percentage < 100)
    display.write("SC0"); display.write(0x01);
    display.write("FR"); display.write((barX+border+1)+(barSplit+1)); display.write(barY+1+border); display.write((barX+barWidth)-1); display.write(barY+barHeight-(border*2)); display.write(0x01);

function updateDisplay()
  local wifiDB = imp.rssi() + 87;
  wifiDB = (87.0/100.0) * wifiDB;

  progressBar(49, 14, 8, 77, 1, wifiDB)

  imp.wakeup(0.1, updateDisplay);

This will then update the bar chart every 0.1 second.


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