• Overview
• Installation
• Software
• Connections
• Model Types
  • Model One
  • Model Two
  • Model Three
• Tested
• Notes
  • Swapped data nibbles
  • Read buttons anomaly
  • Multiple displays
  • Multiple buttons pressed together

• Name: TM1638plus
• Description:

An Arduino library to display data on a 8-digit TM1638 seven segment module's. This library supports all 3 of the known models on market. see Model type section below

• Main Author: Gavin Lyons.

The library is included in the official Arduino library manger and the optimum way to install it is using the library manager which can be opened by the manage libraries option in Arduino IDE. Search "tm1638" in search bar of library manager to find it.

See link below for instruction for this and for the other methods too.

Installing Additional Arduino Libraries guide

The API (application programming interface) html documentation is at link. Hosted on github pages and generated by Doxygen software. Here the user will find lots of information on files, functions & data types.

Software API Url Link

Connections to MCU:

* GPIO = STB = Strobe
* GPIO  = CLK  = Clock
* GPIO = DIO = Data input / output
* GND
* VCC 

This library supports three variants of the TM1638, which for purposes of this documentation, will be named Model 1 ,Model 2 and Model 3. Pictured left to right.

TM1638 Module 8 Push buttons 8 LEDS (LED & KEY)

This variant consist of an 8-digit seven segment display with decimal points, 8 Leds and 8 Push buttons. Two 4 digit 3461AS-1 (.34 inch, 4 digit ,common Cathode, decimal point, RED) are used in this module giving a total of 8 digits. A TM1638 controller chip drives the unit. The unit is marked (LED & KEY).

The library support ASCII ,text ,Hex and allows for setting individual segments, and the decimal point of segment. User may have to "debounce" the button read method depending on application. debouncing left out to minimise library size. Example files show some methods to do this. User can Adjust brightness of module. Support 8 degree brightness adjustment. It is possible to manually set segments to create custom patterns without reference to the ASCII font.

TM1638 Module 16 Push buttons (16 KEY) (QYF).

They consist of an 8-digit seven segment display with decimal points, and 16 Push buttons.Two 4 digit 3461BS-1 (.34 inch, 4 digit ,common Anode, decimal point, RED)are used in this module giving a total of 8 digits. A TM1638 controller chip drives the unit. NB : If your display shows "56781234" for "12345678" see Notes section. Note 1.

User may want to "debounce" button's read method depending on application. See TM1638plus_ADC_TEST_Model2.ino for debounce button example. Two different functions to read buttons. Raw ASCII data can be printed without reference to font file.

There are different PCB's of these modules on market, This library was tested on no 3 below. I think this software will work for all of them and the differences in PCB are related to connectors, layout and component placement. This module is a variant of Model 1. The differences are the LEDs are bigger and bi-color both red and green, The seven segment display is larger and extra connectors are added for Daisy chaining. Two 4 digit KYX-5461AS-7.3 (.54 inch, 4 digit ,common cathode, decimal point, RED)are used in this module giving a total of 8 digits.

1. LKM1638 v1.1
2. LKM1638 v1.2
3. TM1638 V1.3

Model 3 LED Functions

The code is the same as model 1 and there is one unique model 3 example file. setLED and setLEDs functions behaviour is the only difference in code base between 1 and 3. SetLED: The difference is when you call the setLED function you pass the following to get LEDs to change colour. For more detailed information on functions see commented headers in header file(.h).

SetLEDs: When you pass call the setLEDs function you can pass a word pattern where upper byte is turns LEDs green on and lower byte turns LEDs red on . Model one ignores lower byte, Set to 0x00 always.

1. Model 3 setLEDs(word) = 0xGGRR
2. Model 1 setLEDs(word) = 0xRR00

• Tested on following MCU & Development platforms.
• Examples files are set up for Arduino UNO & NANO v3.
• File GPIO_OTHER_MCUs.txt in extra folder gives pins tested for other MCU.

1. Arduino UNO & NANO v3 .
2. ATtiny85 .
3. ESP32.
4. STM32 STM32F103C8T6 "the blue pill".
5. ESP8266.
6. Teensy 4.0. (may not work at highest frequency see note #2 in notes section)

Model 2 only. For Some users using this library the nibbles in information display byte where swapped around. This is because there are different versions of modules on market with different wiring. See issue #3 on github called Swapped display :: "12345678" becomes "56781234". If you test library and you see this issue, in order to fix this when you declare the Object, set the fourth parameter "swap_nibbles" to True, The default is false.

Read buttons anomaly on High frequency micro-controllers. This library uses a software SPI-like protocol and may not work fully on micro-controllers running at a very high frequency, without some adjustments to timing. It is a SPI-like interface with a single bidirectional data wire DIO. The TM1638 is basically a slow SPI device (< 500kHz) in DIO mode. The clock uses the equivalent of SPI mode 3 (normally high, clocks data on the rising edge). The problem is that the native Arduino shiftIn()/shiftOut() wire functions are simply too fast for this device (technically the clock signalling for the TM1638 is inverted but as it triggers on a rising edge still it is tolerant of that). To make this work with fast devices, the shift clocking is slowed with a small delay (on the order of a microsecond).

HighFreqshiftin function:

As of version 1.6 a new parameter (_HIGH_FREQ) has been introduced to constructor it is false by default. Set to true for high frequency MCU ~> 100Mhz. This should fix the issue of HF MCU not reading buttons correctly(ESP-Xs). The High_Freq parameter causes a custom shift-in function to be used. The delay in this function is fixed at 1 uS, it can be changed manually by adjusted the defines in common header file.

The Teensy results have been sent in by email, I don't have these MCU's them at time of writing.

Driving multiple displays. It is possible to drive multiple modules. Share the DIO and CLK lines and use a unique STB line for each device. see issue number 10 at github for example code.

Detecting multiple buttons pressed together.

Model 1 and Model 3 CAN detect multiple buttons pressed.

Model 2 has two different functions:

1. ReadKey16 returns a byte with decimal value 1-16 this function cannot detect multiple buttons pressed.

2. ReadKey16Two returns a 16 bit integer where each bit corresponds to the 16 switch's. However due to the wiring of the module, see SG-X lines on schematic, Pressing Certain combinations of buttons will cause the data on Seven Segments to change. So the simultaneous use of multiple key presses and the seven segments display is problematic. See issue 12 on github for more details.