Building a 70cm FM radio using the DRA818 chip & an arduino

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Building a 70cm FM radio using the DRA818 chip & an arduino

Postby M0UKF on Thu Nov 15, 2018 7:14 pm

Hey;

Decided to order myself a 1w UHF module to try building myself a small FM radio - does anyone have any experience with this chip - http://www.dorji.com/docs/data/DRA818U.pdf
Last edited by M0UKF on Sun Nov 25, 2018 12:00 pm, edited 3 times in total.
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Re: DRA818

Postby M0UKF on Sat Nov 17, 2018 9:43 pm

New Arduino kit arrived. First time playing with one so just working some bits out.

For now i don't have the radio components so its just learning how to code in Sketch.

Happy with progress so far - 2 LED's - 1 Power, 1 for Tx

An LCD Display. Volume and Frequency controlled by the X and Y direction of an analogue control stick.

More a proof of concept for now.

20181117_213445.jpg


20181117_213433.jpg


Also just noticed i have the wrong pretend frequency showing, the final device will be on 70cms
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Re: DRA818

Postby 2E0VZK on Sat Nov 17, 2018 10:07 pm

That looks like a fun project, keep us up to date with how you get on.
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Re: DRA818

Postby M0UKF on Sun Nov 18, 2018 6:20 pm

Shall do.

For now here's a brief video of the proof of concept - ie basic frequency control and menu system https://youtu.be/zECNHdbzwgs
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Re: DRA818

Postby M0UKF on Sat Nov 24, 2018 7:48 pm

So minor update.

I've not got all elements bar the Transceiver setup and talking to each other through the Arduino.

The project looks like a rats nest of cables but a mini demo is here:

https://www.youtube.com/watch?v=zzZ2lrbPajo

The code behind the radio so far is on github

https://github.com/m0ukf/70cmArduino/blob/master/M0UKF.ino

I'm not certain i'll maintain it as i go, but i'll certainly upload the final version when the chip arrives. Be warned, the code is beyond a mess. With ideas that are all over the place! It works but it needs a lot of love!
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Re: DRA818

Postby 2E0VZK on Sun Nov 25, 2018 10:01 am

Looking good!
Like you say the code and the wiring is still in the unpolished stage but there's nothing wrong with that. No point it getting it perfect until its closer to working.
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Re: DRA818

Postby M0UKF on Sun Nov 25, 2018 11:58 am

Yeah my biggest headache has been building the code, especially as it's the first time i've touched an arduino - the most interesting part has been working out how to manage the "state" of the radio.

That is, how it knows whether you are in a menu system screen, VFO or even trying to Tx at any given time.

I've ended up with 2 variables one that goes high when PTT is pressed and overrides everything and transmits, and a second state mode variable, currently labelled screenmode so each loop the radio knows what it should be doing.

The idea is that each state mode triggers different code. So 0 is the Welcome screen, 1 is the VFO, 2 is the Menu, 3 is a keypad test screen. When you first turn it on you can scroll between 0, 1, 2 & 3 but no more.

If you are in, for example, mode 2 [Menu] and press Enter on the CTCSS Settings option, the mode gets changed to screenmode 4, the CTCSS settings screen. When you exit screen 4 it always puts you back to screen 1 - allowing you to renavigate the menu.

The only thing i haven't started on is the Serial comms side of things for controlling the 70cm transceiver chip that i ordered in from china. I can do a lot of this before it lands using the PC screen monitor to check the right commands are being issued.

Once the chip lands and i can do that final testing i can work on a proper build, including revisiting the earliest bits of code that made sense at the time but probably need reducing down / reworking to flow more effectively.

It's definitely an interesting challenge of logic.
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Re: Building a 70cm FM radio using the DRA818 chip & an ardu

Postby 2E0VZK on Sun Nov 25, 2018 2:31 pm

Yeah that stuff can be really challenging and flow charts can only go so far in helping you out.
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Re: Building a 70cm FM radio using the DRA818 chip & an ardu

Postby M0UKF on Fri Dec 07, 2018 8:57 pm

Chip arrived!

Initial tests are a success

https://youtu.be/59ZJyUKrnG8
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Re: Building a 70cm FM radio using the DRA818 chip & an ardu

Postby 2E0VZK on Sat Dec 08, 2018 9:37 am

Good stuff :)
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