erriez/errieztm1638

TM1638 LED driver with key-scan library for Arduino

Optimized TM1638 library for Arduino

This is a 3-pin serial TM1638 chip library for Arduino, optimized for size and speed. It supports a combined LED driver controller and key-scan interface to detect multiple key presses at the same time.

Displaying numbers, characters and reading keys depends on the hardware wiring and is not part of this library. A fully operational example for a board with 8 7-segment displays, 8 dual color LED's and 8 buttons which uses this library is available here: JY-LKM1638.

Hardware

Connect power and 3 data pins to an Arduino board DIGITAL pins:

• VDD (Power 3.3V - 5V)
• GND (Ground)
• DIO (Bi-directional data input/output)
• STB (Chip select)
• CLK (Clock)

The following TM1638 pins should be connected to LED's and buttons in a matrix:

• K1~K3 (Key-scan data input to read multiple key presses at the same time)
• SEG/GRID (Output for LED matrix)

Pins

Pin	TM1638	Arduino UNO / Nano / Micro / Pro Micro / Leonardo / Mega2560	WeMos D1 & R2 / Node MCU	WeMos LOLIN32
1	VCC	5V (or 3.3V)	3V3	3V3
2	GND	GND	GND	GND
3	CLK	2 (DIGITAL pin)	D2	0
4	DIO	3 (DIGITAL pin)	D3	4
5	STB0	4 (DIGITAL pin)	D4	5

• Check maximum regulator / diode current to prevent a burnout when using lots of LED's. Some boards can provide only 100mA, others 800mA max.

Example

Arduino IDE | Examples | Erriez TM1638 button and LED driver:

• ErriezTM1638

Documentation

• Doxygen online HTML
• Doxygen PDF
• TM1638 Datasheet

Usage

Initialization

// Include TM1638 library
#include <ErriezTM1638.h>

// Connect display pins to the Arduino DIGITAL pins
#define TM1638_CLK_PIN   2
#define TM1638_DIO_PIN   3
#define TM1638_STB_PIN   4

// Create tm1638 object
TM1638 tm1638(TM1638_CLK_PIN, TM1638_DIO_PIN, TM1638_STB_PIN);

void setup()
{
    // Initialize TM1638
    tm1638.begin();
}

Display on/off

// Turn display off
tm1638.displayOff();
  
// Turn display on
tm1638.displayOn();

Turn all LED's off

// Turn all LED's off
tm1638.clear();

Get keys

// Get 32-bit key-scan
uint32_t keys = tm1638.getKeys();

Write Byte to display register

// Write segment LED's to the first display registers 0x00..0x0F with value 0x00..0xff to
// display numbers and characters. Just an example which depends on the hardware:
tm1638.writeData(0x01, 0x01);

Write buffer to display registers

// Creat buffer with LED's
uint8_t buf[] = { 0b10000110, 0b00111111, 0b00111111, 0b00111111, 0b00111111, 0b00111111};

// Write buffer to TM1638
tm1638.writeData(0x00, buf, sizeof(buf));

Small footprint

Measured with Arduino IDE v1.8.5 without any other peripherals, calling all library functions once:

Board	MCU flash size	MCU RAM size	TM1638 library flash	TM1638 library RAM
Arduino UNO	32kB	2048kB	1840 Bytes	40 Bytes

Optimized timing

The library uses optimized pin control for AVR targets. Other targets uses the default digitalRead() and digitalWrite() pin control functions.

Output Benchmark example:

Board	CLK	Read keys	Write Byte	Write 16 Bytes buffer	Clear display
Pro Mini 8MHz	65kHz	736us	312us	2448us	2224us
UNO 16MHz	125kHz	340us	152us	1192us	1176us
WeMos D1 & R2 80MHz	200kHz	284us	116us	683us	682us
WeMos D1 & R2 160MHz	300kHz	223us	66us	474us	469us

Arduino UNO 16MHz

WeMos D1 & R2 80MHz

WeMos D1 & R2 160MHz

Library dependencies

• The ErriezTM1638Benchmark example uses Erriez Timestamp library.

Library installation

Please refer to the Wiki page.

Other Arduino Libraries and Sketches from Erriez

• Erriez Libraries and Sketches