LichtKrant

Project LichtKrant
350px
Some 3-colour 80x7 pixel moving LED sign
Status	Initializing
Contact	bertrik
Last Update	2019-12-15

Introduction

Found this lichtkrant on the revspace free stuff table.

It is 80 pixels wide, 7 pixels high. Each pixel has two sub-pixels (red and green), so it should be possible to display at least 3 colours (red, orange, green)

Goals:

• investigate if we can drive this with an ESP8266
• investigate whether we can apply some kind of PWM to increase colour depth
• document how it works
• write software for this, so other people can do the same for their display

Hardware

lichtkrantconnector

It consists of a processor board and a LED board.

Processor board

The processor board has a 8052, a flash chip, battery, 32768 Hz crystal, 40 MHz crystal, Altera Max chip. It appears the Altera chip drives two 245 chips which in turn drive the signal to the connector J1 to the LED board.

It takes 5V as input.

The PCB has a text on it: HXITC017_2.PCB

Connector pinout J1

*  J1: pin IC5.A8 -> IC2.A1 -> IC2.B1 -> via ...
                  -> IC1.B1 -> IC1.A1 -> U11.SRCLK
                  -> IC1.B6 -> IC1.A6 -> U1.SRCLK
*  J2: GND?
*  J3: pin IC6.A1 -> IC2.A2 -> IC2.B2 -> via ...
*                    IC1.B2 -> IC1.A2 -> U11.RCLK
*                    IC1.B5 -> IC1.A5 -> U1.RCLK
*  J4: GND?
*  J5: pin IC6.A2 -> IC1.B3 -> IC1.A3 -> U11.SER
*  J6: GND?
*  J7: pin IC6.A3 -> IC1.B4 -> IC1.A4 -> U1.SER
*  J8: GND?
*  J9: pin IC6.A4 -> IC2.A7 -> IC2.B7 -> via ...
                  -> IC4.1A -> IC4.1Y -> IC3.G2B
* J10: VCC?
* J11: pin IC6.A5 -> IC2.A3 (row) -> IC3.A
* J12: VCC?
* J13: pin IC6.A6 -> IC2.A4 (row) -> IC3.B
* J14: VCC?
* J15: pin IC6.A7 -> IC2.A5 (row) -> IC3.C
* J16: ???
* J17: pin IC6.A8 -> IC2.A6 -> IC2.B6 -> IC3.G2A
* J18: ???
* J19: ???
* J20: connected to the "ethernet" dipswitch

IC2.A7 <- IC4.1A <- via
          IC4.1A -> IC4.1Y -> IC3.G2B

• IC1 = 74HC245 (oct buf)
• IC2 = 74HC245 (oct buf)
• IC3 = 74HC138 (3-8 mux)
• IC4 = 74HC04 (hex inverter)
• IC5 = 74HC245 (oct buf) on CPU board
• IC6 = 74HC245 (oct buf) on CPU board
• U1 = lower chain of 595
• U11 = upper chain of 595

There are 8 rows (3 bits). Two chains of 10x595 (each) for the columns.

So it basically looks like a 9 bit bus.

• 3-bits row select
• ...
• ...

Levels on the bus are 5V (so can we drive it with an ESP?)

LED board

The LED board contains the actual pixels, organized in 16 modules of 5x7 LEDs. Each LED has a red sub-pixel and a green sub-pixel, so it can do colors: red, green, orang The LED modules have the text GYXM-G2357ASRG on them.

The PCB has a text on it: HXBI80070509.PCN, date 2007-12-28

The are already electronics on it, consisting mostly of 595 chips (serial shift registers).

There is an '138 chip (3-to-8 decoder) that drives a set of MOSFETS, 7 in total, so probably the row select.

The MOSFETs are SDM4953, dual P-channel MOSFETs.

Links

Possibly useful other info:

• https://medium.com/@tharindu_peiris/p10-led-display-panel-using-esp8266-wemos-d1-mini-nodemcu-1e463ad60722