LED Matrix

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We have 8 LT1441M display modules that have been donated by Michael Erskine. 'RepRap' Matt started working on getting Arduino talking to the displays.

Datasheet

Git Hub Repo

Talking to the Displays

The displays uses shift registers in order to control the LEDs. There are 256 LEDs per panel, that's 2048 in total. Data is shifted out over the GSI and RSI pins in time with the CLOCK. After clocking out all 2048 pixels, LATCH the data.

Below is an modifed version of the Arduino shiftOut that out puts data on both GSI and RSI pins for the same clock cycle.


void shiftOutDual(int dataPin, int dataPin1, int clockPin, int bitOrder, int val, int val1){

	int i;

	for (i = 0; i < 8; i++)  {
		if (bitOrder == LSBFIRST) {
			digitalWrite(dataPin, !!(val & (1 << i)));
			digitalWrite(dataPin1, !!(val1 & (1 << i)));
		}else{
			digitalWrite(dataPin, !!(val & (1 << (7 - i))));
			digitalWrite(dataPin1, !!(val1 & (1 << (7 - i))));
                }

		digitalWrite(clockPin, HIGH);
		digitalWrite(clockPin, LOW);

	}

}

Connectors

Power: JST VH connector: http://www.jst.co.uk/productSeries.php?pid=133

Led-matrix-con2.jpg
Pin No. Name Function
1 V1 Power supply for LED (red)
2 GND1 Ground for IC
3 VDD Power supply for IC
4 GND2 Ground for LED
5 V2 Power supply for LED (yellow-green)

Data: JST XH connector: http://www.jst.co.uk/productSeries.php?pid=136

Led-matrix-con1.jpg
Pin No. Name Function
1 GSI Serial data yellow-green
2 /GAEO Output enable for yellow-green
3 LATCH Latch contents of shift register
4 GND1 Ground of IC
5 CLOCK Clock Signal for data (read on L->H)
6 /RAEO Output enable for red
7 RSI Serial data red