ScarlettScroller

This page is about a lichtkrant, bought by flok.

Hardware

It has of 16 blocks of 5x8 LEDs, for a total of 80x8 LEDs. It is unknown if it's monochrome (just red) or two-color (red + green).

The electronics consist of two parts: a controller board and a LED board.

The LED board has the following ICs:

• SN74HC138: 3-to-8 line decoder/multiplexer
• SN74HC04: 6 inverters
• 10x SN74HC164: 8-bit parallel-out serial shift registers
• 4x APM4953: dual P-Channel Enhancement Mode Mosfet

The boards are connected through a 10 pin connector. There is also a 5V connector.

Only inverter 1 and 6 of the hex inverter is actually doing something.

Theory of operation

There are 80 pixels horizontally and 10 serial-parallel chips with 8 outputs each, so one row of pixels can be kept in the shift registers.

The 3-to-8 decoder selects one particular row to light, through pins A/B/C. The MOSFETs are used as drivers.

The SCLK signal goes to the CLK input of all serial-parallel SNHC164 chips.

The LED board is prepared to be used with R+G LED modules, however this particular board does not have the shift register populated for the dual-color.

Connector

Pinout:

• pin 1: SCLK
• pin 2: SCLK (shorted to pin 1)
• pin 3: G = 'green' data bit shifted into row, goes through inverter 6
• pin 4: R = 'red' data bit, goes through inverter 1
• pin 5: A = column select
• pin 6: B = column select
• pin 7: C = column select
• pin 8: D = not clear what this is, perhaps this is just another bit for the line selector, not actually used for this particular board
• pin 9: GND
• pin 10: GND