Tester for driving the LED displays on a GamePlan pinball machine

The displays are LED "ttl" driven (has a 7417 in the original schematic, with a clamping diode on the output)

What needs to be driven:

For Display Data: Bit0 Bit1 Bit2 Bit3

For Digit Control: Digit 0 Digit 1 Digit 2 Digit 3 Digit 4 Digit 5 Digit 6

For which Display module (rising edge locks in data): Clk1 Clk2 Clk3 Clk4 Clk5

Overall Display Control: Enable (Acitve Low)

Overall: Since all same digits are tied together on enable (Digit0 on all boards are wired together), we need to:

Set Enable = Low For each digit: For each display: Load Data on Bit0-Bit3 Pulse Clck data line for display Pulse Digit line (low to high)

Alowed Digits (based on 74ls48 datasheet): 0-9 shows the respective digit 10 = [ (really a c, the lower part of the display) 11 = ] (backwards c, the lower part of the display) 12 = u (on the top of the display) 13 = c + _ (top display c with a _ at the bottom) 14 = t 15 = blank (nothing displayed)

Use of serial buffering: 74HC595: Pin 14 = serial data in Pin 11 = shcp clock data in (every serial bit in, latches into the register ) Pin 12 = stcp clock data out (latch on the outputs )

We are going to daisy chain the 595s, so we send 24 bits every time before stcp / latch out

74HC595 for digit control (first in chain - pin 4 on rasp pi to pin 14 on 595) 74HC595 for clock control (second in chain - pin 9 to pin 14) 74HC595 for data control (third in chain - pin 9 to pin 14)

3333 3333 2222 2222 1111 1111 SND- DATA CLOCK- -DIGITS-

SND = Sound board control (when ready)

From https://github.com/google/periph/blob/master/host/rpi/rpi.go

P1_13 gpio.PinIO = bcm283x.GPIO27 // Low, <<--Data In - pin 14 on lsb 595 P1_14 pin.Pin = pin.GROUND // P1_15 gpio.PinIO = bcm283x.GPIO22 // Low, <<--Clock Data - pin 11 on '595s P1_16 gpio.PinIO = bcm283x.GPIO23 // Low, <<--Latch Data - pin 12 on '595s