Morse code to ASCII converter using vhdl

Question

I want to implement a Morse code to ASCII converter in vhdl and then to transmit that ASCII character to PC terminal through UART. I have completed the UART part.

But i don't know how to implement the converter part. The problem is with varying symbol rate of input Morse code. I want to detect dot, dash, character space and word space.

Please help me for the following implementation:

1. detection of Morse code symbols with variable symbol rate
2. binary search tree to traverse the Morse code tree to find the corresponding ASCII character.

Answer 1

It seems as if you're planning to do the converter in two stages, which sounds like a decent idea - first stage for decoding dots, dashes and pauses, second stage for assembling these into characters.

For the first stage, you'll need to define some minimum and maximum timings for your input - that is, what is the shortest and longest a dot / dash / etc can last (I'd take it there are some standards for this?).

With these timings it should be possible to use a counter and an edge detector to decode your input morse signal.

For the second stage, you can create a finite state machine or maybe even just a look-up-table to decode the incoming dots and dashes of a single character, and send this along to your UART.

Answer 2

You need to create a module which sample your input and from the pattern you record, use some fixed pattern to out the corresponding letter. You need to study the width of your received signal to estimate how much your sample rate should be. You can try to read and understand the following shared code on github. https://github.com/altugkarakurt/Morse-Code-Converter which will do the reverse process of generating morse code. This can be used as a test generator for your Morse Reader. The code ASCII extract from Morse detector can be feed into a FIFO, which is a standard circuit and connected to your UART. The Morse detector write the ASCII into the FIFO if the FIFO is not full, while the UART read the ASCII from the FIFO and transmit it to the UART. The FIFO acts as a buffer. If you need some standard UART code look at the Xilinx website which has one UART part of the Microblaze design, it is very simple to interface it.