Project: 4 applications for TM1637 seven segment display circuit connected to Bolt 18F2550 microcontroller

Author: Moises Melendez Reyes

Figure 1:  Display TM1637 is connected to the auxiliar port of Bolt 18F2550 board


Figure 2: additional devices assembled to test TM1637 applications


1. Overview:
The TM1637 device, 7-segment display with 4 digits is an inexpensive circuit, simple to incorporate to microcontrollers. The connection is performed using the protocol known as TWI (two wire interface) with 4 signals: Vcc, GND and 2 signal for the synchronous serial interface.

In this project the development of 4 applications for this display and 18F2550 Bolt system is described:
* Real time clock. The user must enter data using the keypad. The LCD display shows data, including seconds.
* Programmable timer, with input of minutes and seconds from the keypad. The relay is activated when the count reaches zero.
* Digital thermometer in Celsius, with reading from DS18B20 temperature sensor.
* Basic test program: decimal


2. Assembling the system:
Assemble all devices as shown in photos of Figures 2 and 3. The TM1637 four pin connector is directly compatible with the auxiliary port of Bolt 18F2550 system. The user can make the connection directly or through dupont type cables.

Optionally, it is possible to feed the Bolt card either through a USB cable from a PC computer, or through an AC/DC external adapter as shown in Figure 2.


Figure 3: pins of TM1637 are compatible with Bolt 18F2550 auxiliary port


3. Control Program:
The entire project done for Bolt 18F2550 system with the environment MPLAB IDE and C18 compiler is included in the following file. The .hex executable file is in the folder named 'release'. It also contains a manual system operation.


Once the executable file is loaded in the Bolt card, the following 4 applications are available and are selectable via dip switches SW1 and SW2 of Bolt system, depending on the following table. If the selection is changed, the reset button on the Bolt card must be pushed  to activate the new application.

Important notice: the dip switches SW3 and SW4 must be in the OFF position to prevent them from interfering with the operation of the display.


ON ON Displays time in 24 hour format. Input time from keypad.
ON OFF Displays temperature in degrees centigrades
OFF ON Basic test program. Displays decimal counter from 0000 to 9999
OFF OFF Timer application, with a range of 1 hour. Input data from keypad. Activates relay when count reaches 0