Nov 192016

I was looking for a recipe of something my grandma made. She called it “Gebackenes Zeug” which unfortunately is not a proper name. it contained Quark and mashed potatoes, but that’s all I knew. But today I found something which is at least similar if not identical except for the shape: Sächsische Quarkkeulchen. Here the recipe:

Zutaten für die Quarkkeulchen
500g Pellkartoffeln
500g abgetropfter Magerquark
150g Mehl
40g Zucker
70g Rumrosinen
Mark von ½ Vanilleschote
1 Eigelb
Abrieb von ½ Zitrone
Butterschmalz zum Braten
Puderzucker zum Bestäuben

Zubereitung der sächsischen Quarkkeulchen
1.    Die Kartoffeln weichkochen, pellen und durch die Kartoffelpresse drücken. Mit den restlichen Zutaten zu einem Teig vermengen.
2.    Aus dem Teig gleichgroße Quarkkeulchen formen und in heißem Butterschmalz beidseitig goldgelb ausbraten. Kurz vorm Servieren alle Quarkkeulchen mit etwas Puderzucker bestreuen.

Taken from here. Being in Japan means: no Quark, so I used Philadelphia cream cheese. I also added ascorbic acid (AKA Vitamin C) to make it a bit sour. No rainsins as I had none. No egg as cream cheese has enough fat. No lemon since I had none. And I had to use normal butter instead of clarified butter. No powdered sugar either.

So I had to change it a lot and I only used 3 potatoes and about 150g cream cheese. Turned out to be tasty though and it’s definitely similar to “Gebackenes Zeug”.

Will try again. Will make pictures then.

Nov 192016
Orange Pi Zero - Neat

Got myself a (actually two) Orange Pi Zero: US$7, quad core ARM Cortex A7@1.2GHz, 256MB RAM, WLAN, FastEthernet, 1 USB, USB-to-go for power. All in a (about) 5×5 cm² package. Add in a 8GB microSD card, and it’s a small capable little board.

While the memory looks on the small side, itś plenty to run one program. Armbian uses about 40MB itself when running:

harald@opz1:~$ free 
              total        used        free      shared  buff/cache   available 
Mem:         247012       36720      142740        2168       67552      193175 
Swap:        131068           0      131068

leaving >200MB left. Given that I can have a (small, limited) web server runnig on an ESP8266 with about 40KB RAM, 256MB is plenty for a single-purpose server/controller.

Ethernet works (as expected). WLAN works via simple nmtui command.

Controlling the 2 LED’s is easy too:

root@opz1:/# cd /sys/class/leds/red_led 
root@opz1:/sys/class/leds/red_led# ls 
brightness  device  max_brightness  power  subsystem  trigger  uevent 
root@opz1:/sys/class/leds/red_led# echo 1 >brightness  

That turns on the red LED. Similar for the green LED.

To find out what GPIO’s exist, use this:

root@opz1:/sys/class/leds/red_led# cat /sys/kernel/debug/gpio                                              
GPIOs 0-383, platform/sunxi-pinctrl, sunxi-pinctrl: 
 gpio-10  (?                   ) out hi 
 gpio-17  (red_led             ) out hi 
 gpio-202 (xradio_irq          ) in  lo 
 gpio-354 (?                   ) out hi 
 gpio-362 (green_led           ) out hi

To export a GPIO, do

# echo 15 >/sys/class/gpio/export

and then in /sys/class/gpio/gpio15/ you can see the standard Linux kernel GPIO things like direction (in/out) and value (0/1)

See also the schematics which show what port of the H2+ connects to what thing: orange-pi-zero-schanetics-v1_11 (sp!)


Nov 062016

During today’s Dev Japan Meetup I finally had the time to do something I always wanted to do but never had time to implement: Create a fast link from an end-device (AKA browser or phone application) to my LED display. That display is a simple 10×10 WS2812 LEDs strip originally connected to an Arduino with a Bluetooth receiver, but replaced by a Wemos D1 mini flashed with Espruino since that has WiFi and more RAM.

Here the important (but incomplete) part of the Espruino program:

var host = "";
var WebSocket = require("ws");
var ws = new WebSocket(host,{
  path: '/',
  port: 8080, // default is 80
  protocol : "echo-protocol", // websocket protocol name (default is none)
  protocolVersion: 13, // websocket protocol version, default is 13
  origin: 'Espruino',
  keepAlive: 60

ws.on('open', function() {
  console.log("Connected to server");

ws.on('message', function(msg) {
  console.log("MSG: " + msg);
  if (msg == "R") {
    colorize(40, 10, 10);
  } else if (msg == "G") {
    colorize(10, 40, 10);
  } else if (msg == "B") {
    colorize(10, 10, 40);
  esp8266.neopixelWrite(NodeMCU.D4, leds);

The logic is as simple as it looks: connect to a WS server and wait for incoming messages. If it’s “R”, or “G”, or “B”, then colorize the LED array.

Here a section of the browser part:

var ws = new WebSocket("ws://");

ws.onopen = function(evt) {
  var conn_status = document.getElementById('conn_text');

ws.onmessage = function(evt) {
  var newMessage = document.createElement('p');
  newMessage.textContent = "Server: " +;

ws.onclose = function(evt) {
  alert ("Connection closed");

$(".color").click(function(evt) {

and the buttons look like

<button type="submit" class="color" val="R">Red</button>
<button type="submit" class="color" val="G">Green</button>
<button type="submit" class="color" val="B">Blue</button>

The one missing part is the websocket server in the middle which relays messages, which I took quite literally from here from the Espruino Websocket docs.

This is anything but clean code, and not yet a complete and instructive example application, but it’s the first step and a good proof-of-concept.

Next step is a web page to have a 10×10 grid of buttons which can be turned on/off by touching, and the corresponding commands are sent to the LED display.