When [Mike] ran across a display on Deal Extreme with 8 seven-segment displays, 8 red/green LEDs, and 8 buttons, he knew it would find a good home in a future project. There was only one problem, though: except for an Arduino library, there was absolutely no documentation available for this display. Wanting to use this display with an FPGA board, [Mike] decided against bit-banging a protocol and ported the C++ code into a hardware implementation.
This Deal Extreme display, the TM1638, features enough seven-segment displays, LEDs and buttons to build something really cool, and surprisingly isn’t terribly hard to interface with a microcontroller. The TM1638 library communicates with the outside world via only three pins and a simple serial connection.
After figuring out what commands are sent to make the display turn LEDs on or off, [Mike] wrote a hardware implementation for his Digilent Nexys2 and Digilent Basys2. Now the display operates on an FPGA just like it does with an Arduino, and is a great tool for debugging HDL code for [Mike]‘s FPGA.
Subscribe for weekly videos
Nice work. It could be usefull.
yeah, especially since the undocumented displays are usually the lowest priced ones on the surplus sites.
There actually is documentation; one of the folks at the DealExtreme forums translated the Chinese datasheet into english.
The device uses a straightforward 3-wire SPI interface (strobe, clock, and a bidirectional serial pin).
I ended up bit-banging the protocol on my MSP430, but there is a library out there on the 43oh forums that uses the hardware SPI interface (and a couple external diodes) to make it work without bit-banging.
Nice find! That chip actually looks pretty useful… can drive 80 LEDs and 24 switches.
If I was still into Flight Sim it would be a cockpit builder’s dream chip :-)
Actually there is documentation, but in Chinese. You can download the datasheet of the TM1638 on the manufacturer’s website (titanmec.com). Timing diagrams are a universal language, and in case of doubt automatic translation usually works well with Chinese.
http://code.google.com/p/tm1638-library/
Not sure if this is helpful info but Ricardo has already done work on this with some C++ libraries.
–Aaron
I actually had plans to build the Arduino library using SPI too, but it was simple to try and test it and get it to work using the bit-banging than SPI.
Just never had time to pick it up, but it’s on my TODO list to pick it up and use the SPI on arduino too… someday :)
I it was your library code that I worked from, so a big public “thank you” is needed.
Thank you!
Now I must be able to do something grand with this display… I’m thinking of using a GPS module to get my car’s car speed, and then using a row of three of these to make a POV display that displays “I am going X km/hr” as I drive down the street. It can use the speed info to adjust the aspect ratio.
Won’t be doing it on and FPGA though :-)
Try this one, works very similarly https://dx.com/p/jy-mcu-16x-digital-tube-yellow-led-module-104311 It’s a bit fiddly to get the right numbers to the right segments, but it works well.
That’s a TM1640, not a TM1638. It’s similar, but not exactly the same. There’s support for that in the library too.