Launchpad based serial Morse code transmitter

This project shows how to build a small Morse transmitter using the MSP430G2231 microcontroller.

The device can transmit in two modes:

-Serial interface, gets characters from a COM port and converts them to Morse code

- Through the manual, use the keys to encode.

In serial mode, reads and transmits Morse code one character at a time from the COM port at a rate of 15 words per minute. To better understand how Morse code works, read this.

The output pin of the Morse key is connected to a pin of the microcontroller as an encoding pin, thereby obtaining a pure CW mode (CW mode refers to single carrier mode, that is, the output frequency is a single-frequency signal, and its corresponding modes include sweep frequency mode or modulation mode, etc.).

The device is powered by two AA batteries and remains in a continuous low-power mode when not transmitting. You should add a second power supply for the octal buffer using four AA batteries to boost the RF power.

Step 1: Bill of Materials and Tools

Here's what you'll need for this project:

Bill of Materials

- MSP430G2231 microcontroller from Texas Instruments

-1 74HC240 octal buffer (74HC240 is a powerful three-state buffer, which integrates 8 reverse buffers with Schmitt trigger input characteristics.)

- 1 crystal oscillator (operating frequency should be in 10/12m CW band (24/28Mhz))

- 2 220 ohm resistors

- 2 1K resistors

- 2 LED indicators (different colors would be best)

- 2 buttons (already included in Launchpad, you can choose a comfortable button for Morse code keys)

-2 AA batteries (you may want to use a separate 6V (4AA) power supply for the 74HC240)

-1m wire (9 AWG standard)

tool

-iron

-Solder

-Wire stripper

- Solderless breadboard or strip copper foil breadboard

-TI Launchpad

-mini-usb cable[page]

Step 2: Hardware and Circuit Diagram

As you can see from the schematic, a microcontroller is used to give the Morse code an on-off switch.

The oscillating output is fed into an octal buffer; the amplified signal is then transmitted via a long wire antenna.

LED1 will show the mode of operation (Serial or Manual) and LED2 will indicate whether the device is transmitting.

When the push button is pressed for the first time, the device will enter manual mode: the following presses will act as normal Morse coding keys to send Morse code

To return to serial mode, just press the RST button.

You can easily build a Morse transmitter using a breadboard and a Launchpad (although it might be a bit too messy).

As you can see from the photos, I have roughly done it on a Launchpad, but I will make a dedicated PCB in the future.

Step 3: Software

The program will send the code over and over again until the UART receives the data, then encode the received data into Morse code, load the combination of dots and dashes to the output pin, and finally return the data

The code is very clearly commented, so you shouldn't have any trouble understanding it.

The difficulty came when I needed to build a Morse code table, because there is no known algorithm that can directly translate the serial input into Morse code. In order to fit the 512 bytes of RAM on the G2231, I had to use some combination of dots and dashes.