Add FM Demodulation

[drewby08]

Adding basic FM demodulation and playback using rtl_fm and aplay.
Commented out the SDL environment variables to get it working on my touchscreen.

How To Use:

• Press Config
• Set Center Frequency
• Go Back
• Press Demodulate
• Plug in 3.5mm headphone jack and listen

[ladyada]

thanks, what hardware was this tested on?

[drewby08]

Tested on following platform:

• Raspberry Pi 3
• OS: Jessie
• Kernel: 4.4.50-v7
• Touch Screen: http://www.lcdwiki.com/3.5inch_RPi_Display
• RTL-SDR: https://www.nooelec.com/store/sdr/nesdr-smart-sdr.html

[ladyada]

that uses a different display so maybe thats why you had to remove some SDL lines, please add those back

[drewby08]

Ok, added the SDL environment variables back ✅

[ladyada]

@makermelissa any interest in trying?

[alphafox02]

nice work! I have brand new never used pi 3 b’s, exact screen, and rtl dongle in adafruits post. I have a small class to teach and this will be perfect if I can get the fm demodulation working. Is all of this included in the fork? Should I stick with the older pi images and not attempt on buster?

[drewby08]

nice work! I have brand new never used pi 3 b’s, exact screen, and rtl dongle in adafruits post. I have a small class to teach and this will be perfect if I can get the fm demodulation working. Is all of this included in the fork? Should I stick with the older pi images and not attempt on buster?

Yep my fork should have everything you need. I haven't tested on Buster, so if you want to play it safe just go with the older Jessie release.

[alphafox02]

Gave this a try,

https://learn.adafruit.com/adafruit-pitft-3-dot-5-touch-screen-for-raspberry-pi/easy-install-2

Which had me install the stretch image. Everything works with the touch screen prior to starting freqshow, however both your fork and the original does not seem to recognize any touch on the screen except for maybe it goes full screen, so unfortunately unusable. I’ll revert to the older Jessie image for this pi 3 b and do the setup again.

[drewby08]

Gave this a try,

https://learn.adafruit.com/adafruit-pitft-3-dot-5-touch-screen-for-raspberry-pi/easy-install-2

Which had me install the stretch image. Everything works with the touch screen prior to starting freqshow, however both your fork and the original does not seem to recognize any touch on the screen except for maybe it goes full screen, so unfortunately unusable. I’ll revert to the older Jessie image for this pi 3 b and do the setup again.

The changes in red here on this diff are what I had to do to get touchscreen working on my setup: https://github.com/adafruit/FreqShow/pull/21/files/405eab39ec87bb7905a494b9427416464a9a75c2..05197486655519cce329120d525a24715114146c

[alphafox02]

I’ll make the changes and let you know. Not even sure if this would be possible, but would there be any way to add demodulation (if that’s what it’d take) to listen in on FRS?

[alphafox02]

Made the changes in red. Your fork comes up and everything can be interacted with and works except for one thing, no possible way to interact with the demodulation option with touch nor a mouse and clicks on it. I can touch and use a mouse on all other options. I’ll get around I trying Jessie, but it seems so close to working on stretch.

update: it works perfect. I had the hdmi plugged in with the screen being mirrored and realized I had no audio on the jack, also realized nothing really happens when you click demodulation except for the fact it’s just enabling it. I thought a new menu was supposed to pop up. After rebooting with no hdmi plugged in I could set the center freq and listen to the fm channel. So mark it down as it works with stretch using the exact build in the guide I posted above.