The TM1638 Board is a small board with a TM1638 IC, two groups of four 7-segment displays, 8 LEDs and 8 switches.
It is sometimes refered as TM1638 LED&KEY board (do not differ so much from the other boards, like the the QYF-TM1638 and JY-LKM1638)
It is a cheap (around 2$) board, and I have chose to use it because of its price, and its ability to chain several boards and control several LEDs, switches and 7-segment displays from the Raspberry Pi.
The idea (and maybe not the best idea) was to modify it so as to control extern LEDs, switches and bargraph (rather than the onboard ones). For the price, that was a good idea (these board are very cheap, but sometimes with a low finition: LEDs and displays are sometimes unaligned), but it gaves me a lot of work to unsolder the components. A better idea could be to directly buy a TM1638 IC and some 7-segment displays and make my own board (but I was affraid not to have time to make my own board).
The TM1638 is a LED driver controller with key-scan interface, with serial interface. It can drive up to 80 LEDs, and scan up to 24 push-buttons.
The datasheet badly explains how to exchange data with the TM1638, but you can find some tutorials online (this one, for example). Only 3 lines are necessary (plus Vcc and Gnd):
STB: Chip select (Enable)CLK: clock for the serial communicationDIO: Data Input Output
When STB is High, the data between the TM1638 board and the raspberry pi are exchanged using serial communication with CLK and DIO: in input mode (the TM board receive data), the data is read at the rising edge of the clock, and in output mode, the data is sent at the falling edge of the clock.Some library exists (for arduino or Raspberry Pi), in C or in Python. But I was not convinced by the existing python libraries for Raspberry Pi (by their design and API), so I wrote (yet another) one (just for fun) you can find here.
Finaly, I changed my mind and decided to drive the TM1638 from the micro-controller (not the Raspberry Pi), so I’ve ported my library to the AVR (files TM1368.c and TM1638.h)
I wanted to use it to control the different switches and LEDs (and bargraphes) of the different panels.
So, I had to unsolder some leds and switches and sold some screw block connectors.
At first, I wanted to use more than the 8 buttons existing on the board, by using the two unused input lines (named K2 and K3, on pin 2 and 3 of the TM1638), but unfortunately, this is not usable for switches, only for push-buttons (if you have more than 3 switches on in the same time, the result is not valid anymore).
The TM1637 IC is similar to the TM1637, except that it doesn’t have any input, and can only drive four 7-segment displays. That’s perfect for the small displays I need (show the attitude of the spaceship and the speed).
The protocol is a little bit different than the TM1638 since it doesn’t have an STB input (enable).
(to be completed with links and code)