Recording Rapid Serial Port in Arduino from Processing

Question

I need help to speed up writing to the serial number. I found some similar questions for this, but nothing about the processing language or Java, so I hope someone can help me with this question that I have.

change

As John points out below, it seems that the serial number is simply not fast enough to send as much data as fast as I want. Does anyone know of the other arduino interfaces available?

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I use arduino to control a grid of 400 RGB LEDs that I connected. To send commands to arduino, I wrote a small program in Processing, which manages a large array that represents LEDs. Then I try to update the grid by sending 800 bytes of data to the arduino every 20 ms at 115200 bauds in serial. Processing code that is called every 20 ms:

noStroke(); int dataPos = 0; // position in LED data array byte[] dataLedGrid = new byte[400*2]; // array for bytes to send for(int j=0; j<LEDS_TALL; j++) { for(int i=0; i<LEDS_WIDE; i++) { int pos = j*20+i; int r = ledGrid[LEDS_WIDE-i-1][LEDS_TALL-j-1][0], g = ledGrid[LEDS_WIDE-i-1][LEDS_TALL-j-1][1] ,b = ledGrid[LEDS_WIDE-i-1][LEDS_TALL-j-1][2]; int colorData = ((g & 0x1F) << 10) | ((b & 0x1F) << 5) | (r & 0x1F); dataLedGrid[dataPos] = byte(colorData & 0x00FF); dataLedGrid[dataPos+1] = byte(colorData & 0xFF00); dataPos+=2; // draw LED squares on gui fill(ledGrid[i][j][0], ledGrid[i][j][1], ledGrid[i][j][2]); rect(SIDE_PANEL_WIDTH+(LED_SQUARE_SIDE+LED_SQUARE_SPACING)*i+HORIZONTAL_MARGIN, (LED_SQUARE_SIDE+LED_SQUARE_SPACING)*j+VERTICAL_MARGIN, LED_SQUARE_SIDE, LED_SQUARE_SIDE); } } myPort.write(dataLedGrid); // write to serial 

On arduino, I have a 1D array (Display) that represents the grid on the arduino side. Loop code:

 void loop() { unsigned int pos, c1, c2; if (Serial.available() > 0) { for(byte j=0; j<20; ++j) { for(byte i=0; i<20; ++i) { c1 = Serial.read(); c2 = Serial.read(); pos = i+20*j; if(j % 2 != 0) // it a square of leds created by a zigzaging line pos = 20*(j+1)-i-1; // so I have to reverse every other line Display[pos] = (unsigned int)(c1<<8 | c2); } } show(); } } 

Now the code itself works fine, but when serial writing slows everything down. When I run the processing code without sequential writing, everything works fine at a given speed. However, when I add serial input, everything becomes a little volatile. The processor does not maximize or nothing, so I assume this is the serial.write method that I call. What can I do to speed up this code or remove the backlog from serial input?

Thank you for your help!

Answer 1

Do the math.

115200 baud, at 8-N-1, 11.520 bytes per second or 86.8 μs / byte.

After 20 ms, you can send 230.4 bytes. Sending 800 bytes will take about 70 ms.

Attempting to send 800 bytes at 115200 bauds every 20 ms will not work.

Answer 2

Try adding Serial.setTimeout(0) to setup() your arduino sketch