Browser controllable RGB LED

When you have a microcontroller which can connect to the network and it has a RGB LED, the logical step is to make this LED controllable via a web browser.

The list of issues faced is numerous:

• NodeMCU does not handle websockets natively
• Thus a bridge between normal TCP sockets used by NodeMCU and WebSockets used by the web browser is needed: ws-tcp-bridge does that
• ws-tcp-bridge defaults to binary blobs which the browser cannot handle. Switching the websocket’s binaryType to arraybuffer fixes this
• Sending data too fast to a just created websocket which has its binaryType not yet changed to arraybuffer breaks ws-tcp-bridge with a fatal error:
  TypeError: “list” argument must be an Array of Buffers
• NodeMCU uses Lua, the browser JavaScript. The langages are quite similar! See below for an example.

Code is at https://github.com/haraldkubota/rgbled-websocket

Interesting is the comparison of Lua and JavaScript variable names are the same):

for (c of s.split('')) {

  if (c>='0' && c<='9') {
    if (state==1)
      value=10*value+c.charCodeAt()-48;

    } else {
      if (state==1) {
        setOneColor(color, value);
        state=0;
      }
      if (c=='R' || c=='G' || c=='B') {
        color=c;
        value=0;
        state=1;
      }
   }
}

for n=1,s:len(),1 do
   c=s:sub(n, n)
   if c>='0' and c<='9' then
     if state==1 then
       value=value*10+c:byte(1)-48
     end
   else
     if state==1 then
       setOneColor(color, value)
       state=0
     end
     if c=='R' or c=='G' or c=='B' then
       color=c
       value=0
       state=1
     end
   end
 end