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TM1637, TM1638 and MAX7219 Seven-Segment Display

!!! info This feature is included only in the tasmota*-display.bin" precompiled binary

To use this feature (i.e., if you're not using tasmota*-display.bin precompiled binary), you must compile your build after adding the following to user_config_override.h:

#ifndef USE_DISPLAY
#define USE_DISPLAY
#endif

#ifndef USE_DISPLAY_TM1637
#define USE_DISPLAY_TM1637
#endif

In case you want MAX7219 also add:

#ifndef USE_DISPLAY_MAX7219
#define USE_DISPLAY_MAX7219
#endif

To get the config options for GPIO-Pins displayed

TM1637 TM1638 MAX7219
TM1637          TM1638        MAX7219

The TM1637, TM1638 and MAX7219 display modules are small (~ 10mm high digits) 7-segment, LED-based display units with 4/6 digits (TM1637), 8 digits and 8 digits (TM1638 and MAX7219) respectively. They use a two-wire (TM1637) or three-wire (TM1638 and MAX7219) I2C-like (but not exactly) protocol for communication with MCUs like the ESP8266 / ESP32 / Arduino etc.,

These modules are a great way to add a simple numeric display to any MCU project.

Features

The Tasmota support for these modules can --

  • display Numbers and Floats with control over position and leading zeros.
  • display basic Text, for example, sending the text 22.5^ will display:
    22.5d
  • display Raw segments.
  • display Level, like a bar graph
  • display Scrolling text
  • display a Clock in 12 hr and 24 hr format
  • set Brightness (8 levels) and Clear the display.

!!! info This driver does not support the buttons and LEDs on the TM1638

Configuration

Wiring

The TM1637 module needs to be connected to two GPIO pins and a 3.3V-5V power supply.

TM1637 ESP8266 based module
CLK GPIOx
DIO GPIOy
VCC 3.3V (e.g., ESP-01) or 5V (e.g., Wemos D1 Mini)
GND GND

The TM1638 module needs to be connected to three GPIO pins and a 5V power supply.

TM1638 ESP8266 based module
CLK GPIOx
DIO GPIOy
STB GPIOz
VCC 5V
GND GND

The MAX7219 module needs to be connected to three GPIO pins and a 5V power supply.

MAX7219 ESP8266 based module
CLK GPIOx
DIN GPIOy
CS GPIOz
VCC 5V
GND GND

Tasmota Settings

In Tasmota's Configuration -> Configure Module page, assign:

For TM1637

  1. GPIOx to TM1637 CLK
  2. GPIOy to TM1637 DIO

For TM1638

  1. GPIOx to TM1638 CLK
  2. GPIOy to TM1638 DIO
  3. GPIOz to TM1638 STB

For MAX7219

  1. GPIOx to MAX7219 CLK
  2. GPIOy to MAX7219 DIN
  3. GPIOz to MAX7219 CS

For example, if x=0 and y=2, z=4 then the module configuration would look like the following:

TM1637
TM1637

TM1638
TM1638

MAX7219
MAX7219

Initial Setup

The power toggle button in webUI turns the display on or off.

DisplayModel

Once the GPIO configuration is saved and the ESP8266 / ESP32 module restarts, set the Display Model to 15 using the command:

DisplayModel 15

DisplayWidth

If you have a TM1637 with 6 digits, set the number of digits using the command:

DisplayWidth 6

DisplayType

The 6-digit TM1637 has 2 known variants with different hardware wiring for the digit ordering.
You can switch between these two variants with the following commands:

DisplayType 0 - Use this for the Type 0 variant, with wiring similar to the TM1637 4-digit modules
DisplayType 1 - Use this for the Type 1 variant, with a different wiring that causes the text 123456 to appear as 321654

After the ESP8266/ESP32 module restarts again, the display module is ready to accept commands.

DisplayModes

DisplayModes 0..3 are supported. The firmware default is DisplayMode 1.

To use the Seven-Segment specific Display- commands described below, set the DisplayMode to 0 with:

DisplayMode 0

DisplayDimmer

The brightness of the display can be set using the DisplayDimmer command.

DisplayDimmer 0..100 maps the brightness value to 8 steps from 0..7

For a minimum brightness, make sure this value is at least about 13

7-Segment specific Commands

The Display- commands listed below can be used from the Tasmota web-console, MQTT, and from Tasmota Rules

Commands and Usage

Console/MQTT Commands Description values
DisplayClear Clears the display
DisplayNumber Clears and then displays number without decimal. command e.g., "DisplayNumber 1234".
Control leading zeros, length and position.
leading zeros can be 1 or 0 (default),
length can be 1 to NUM_DIGITS (4 or 6),
position can be 0 (left-most) to NUM_DIGITS (right-most).
Command example: DisplayNumber 12, 1, 1, 3 This will display:
012		 num [, position[, leading_zeros[, length]]]
DisplayNumberNC Display integer number as above, but without clearing first. e.g., "DisplayNumberNC 1234". Usage is same as above. same as above
DisplayFloat Clears and then displays float (with decimal point) command e.g., "DisplayFloat 12.34".
Control precision, length and position.
precision can be 0 to NUM_DIGITS (default),
length can be 1 to NUM_DIGITS (4 or 6),
position can be 0 (left-most) to NUM_DIGITS (right-most).
Command example: DisplayFloat 2.48, 1, 1, 2 This will display:
2.5		 num[, position[, precision[, length]]]
DisplayFloatNC Displays float (with decimal point) as above, but without clearing first. command e.g., "DisplayFloatNC 12.34" same as above
DisplayRaw Takes upto NUM_DIGITS comma-separated integers (0-255) and displays raw segments.
Each number represents a 7-segment digit. Each 8-bit number represents individual segments of a digit.
Segment a=1, b=2, c=4, d=8, e=16, f=32, g=64 and h (decimal point)=128.
To turn on all segments, the number would be 1+2+4+8+16+32+64+128 = 255
For example, the command DisplayRaw 0, 2, 255, 255 would display:
8.8.		 position, length, num1 [, num2[, num3[, num4[, ...upto NUM_DIGITS numbers]]...]
DisplayText Clears and then displays basic text. Command e.g., DisplayText a.b12
Control length and position of the displayed text.
length can be 1 to NUM_DIGITS ,
position can be 0 (left-most) to NUM_DIGITS-1 (right-most)

A caret(^) symbol in the text input is dispayed as the degrees(°) symbol. This is useful for displaying Temperature (or angle)!
For example, the command DisplayText 22.5^ will display:
22.5d		 text[, position[, length]]
DisplayTextNC Displays text without first clearing the display. Usage is same as above. same as above
DisplayScrollText Displays scrolling text, upto 50 characters.
If num_iterations is not specified, it scrolls indefinitely, until another Display- command is issued. Optionally, specifying num_iterations causes the scrolling to stop after the specified number of iterations.
Command examples:
DisplayScrollText tasmota is awesome -- causes indefinite scrolling
DisplayScrollText tasmota is awesome, 5 -- causes scrolling to stop after 5 iterations		 text [, num_iterations]
DisplayScrollDelay Sets the speed of text scroll. Smaller delay = faster scrolling. 0 to 15
DisplayLevel Display a horizontal bar graph. Command e.g., DisplayLevel 50 will display:

 0 to 100
DisplayClock Displays a clock.
DisplayClock 1 displays a clock in 12-hour format.
DisplayClock 2 displays a clock in 24-hour format.
DisplayClock 0 turns off the clock and clears the display		 1 or 2 or 0

Usage in Rules

All the above commands can be used in Tasmota Rules, as usual.

For example, a simple digital thermometer can be implemented by connecting a DHT22 Temperature-Humidity Sensor and a TM1637 to a Wemos D1 Mini, and writing a Rule like the following:

Rule1
ON Tele-AM2301#Temperature DO DisplayText %value%^ ENDON

Another example, using a MAX7219 and a SHT3X temp/humidity sensor, with value comparison so dispaytext only fires when the value changes. The first four digits display the temperature and the second four digits dispay the humidity. The DisplayTextNC command is used to leave unused digits illuminated, so both numbers can be independently updated.

Rule1
on sht3x#Temperature!=%var1% do backlog displaytextnc %value%^;var1 %value% endon on sht3x#Humidity!=%var2% do backlog displaytextnc %value%h,4;var2 %value% endon on system#init do power 1 endon

TM1637 Images

TM1637
The TM1637 4-digit module (front and back)




TM1637-Wemos
TM1637 4-digit module with Wemos D1 Mini