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Step 3Drive the board
This is the tricky bit. You need to use something (probably a microcontroller) to drive the board in a way which generates an image. Attach power and data cables to the connector in the bottom right of the board. Seen from above, we number the six pins:
1 2 3
4 5 6
The corresponding signals are:
1. XVOLTS - drive voltage for LEDs. Connect to 4V current limited supply.
2. SERIAL_CLOCK - shift data from SERIAL_DATA on positive-going edge.
3. SERIAL_LATCH - latch 40 bits from shift register to LED control on positive-going edge.
4. GROUND - common ground.
5. 5VOLTS - supply voltage for control circuitry. Connect to 5V supply.
6. SERIAL_DATA - input data for shift register.
To scan the display, clock 10 4-bit numbers into the shift register. To clock in a bit:
- bring SERIAL_CLOCK low
- modify SERIAL_DATA
- bring SERIAL_CLOCK high
Once 40 bits have been clocked in, the SERIAL_LATCH signal can be brought high to transfer them to the LED control circuitry. Each 4 bit number selectively enables the red, green and blue LEDs in one row, and selectively disables all LEDs in one column. So if we clock in a string:
0011 0100 0111 ...
RGCB RGCB RGCB
This sets all the LEDs in row 0 to blue, all the LEDs in row 1 to green and all the LEDS in row 2 to cyan (green + blue). It disables all the LEDs in columns 0 and 2. By rapidly clocking in various combinations of values (typically with only 1 of the 10 column-disable bits low), we can scan the array to build up an image, and use pulse-width modulation to give a range of apparent intensities.
The attached firmware can be used with an Atmel ATmega644 to generate the required signals in response to serial input from a PC or Mac.
1 2 3
4 5 6
The corresponding signals are:
1. XVOLTS - drive voltage for LEDs. Connect to 4V current limited supply.
2. SERIAL_CLOCK - shift data from SERIAL_DATA on positive-going edge.
3. SERIAL_LATCH - latch 40 bits from shift register to LED control on positive-going edge.
4. GROUND - common ground.
5. 5VOLTS - supply voltage for control circuitry. Connect to 5V supply.
6. SERIAL_DATA - input data for shift register.
To scan the display, clock 10 4-bit numbers into the shift register. To clock in a bit:
- bring SERIAL_CLOCK low
- modify SERIAL_DATA
- bring SERIAL_CLOCK high
Once 40 bits have been clocked in, the SERIAL_LATCH signal can be brought high to transfer them to the LED control circuitry. Each 4 bit number selectively enables the red, green and blue LEDs in one row, and selectively disables all LEDs in one column. So if we clock in a string:
0011 0100 0111 ...
RGCB RGCB RGCB
This sets all the LEDs in row 0 to blue, all the LEDs in row 1 to green and all the LEDS in row 2 to cyan (green + blue). It disables all the LEDs in columns 0 and 2. By rapidly clocking in various combinations of values (typically with only 1 of the 10 column-disable bits low), we can scan the array to build up an image, and use pulse-width modulation to give a range of apparent intensities.
The attached firmware can be used with an Atmel ATmega644 to generate the required signals in response to serial input from a PC or Mac.
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