We can say one thing for [bitluni]: the BOMs for his projects, like this ESP32 AM radio transmitter, are always on the low side. That’s because he leverages software to do jobs traditionally accomplished with hardware, always with instructive results.
In this case, the job at hand is creating an RF oscillator in the broadcast AM band and modulating some audio onto it. From his previous experience using an ESP32 to watch video on an oscilloscope, [bitluni] knew that the microcontroller’s DACs were up to the task of producing an 800-kHz signal, and he managed to produce a more-or-less sine wave carrier with some clever code. His sketch takes data from a header file, modulates it onto the carrier, and sends it out over the ether using a short stub of wire for an antenna. The range is severely limited, but for what it is, it gets the job done and shows the basics. And as a bonus, [bitluni] included a bit of JavaScript that turns an audio file into a header file that’s ready to go out over the airwaves for all your trolling needs.
If you’re looking for a little more range for your low power transmitter and you’re a licensed amateur operator, you might want to explore the world of QRP radio.
This is great!
I suspect FM would be doable, don’t need a DAC just single GPIO and you don’t have to generate usual FM band ~90MHz directly you can use a frequency with a harmonic in the FM band
Sort of. It is totally doable, since the I2C engine in the ESP32 is similar to the ESP8266. You do have to rely in the reflection around nyquist so the quality isn’t that high, but it does work. One major boon of the ESP32 is the fact it has the second I2C engine so you could actually do sound AND video signals simultaneously.
+1
doable, and we have the second I2S in ESP32.
did you try to push different data on each channel of I2S and measuring the receive?
I wonder if you can just modulate the APLL to generate an I2S clock with say a 3rd or 5th harmonic in the FM band
If you like this, also check out PiFmRds.
Combine with internet radio ESP project and a neat why to repurpose old AM valve sets without ripping them apart and spoiling the oldness.
Anyone succeeded transmitting FM?
Take something like this old maplin scart to vhf converter. [ I like this one, it has dip switches for the channel select ] Very cheap online. Plug it into a tv signal booster and you can transmit old analogue tv. [ someone should be using it. ] granted it won’t go far but you can send your dvds to your old portable in the shed.
https://thumbs1.ebaystatic.com/d/l225/m/myRPWM1MPmNTGsO7vs35bZg.jpg
This is amazing. Are there any projects for simply outputting audio to header pins for a speaker? I see a few resources for plating audio from an ESP, but everything requires an external DAC.
I’ve just stumble upon project (and did a little contribution) which makes ESP32 Bluetooth speaker using A2DP profile, part of it is stereo output to internal DACs.
https://github.com/pschatzmann/ESP32-A2DP/
ESP32 is WAY more powerful than that.. check this out: http://www.fabglib.org/index.html
I am repairing old tube radio’s ans I love this esp32 appliation! I’ll try to extend it with a streaming radio input so that these old AM radio’s get a new purposein their life:=)
Ever figure out how to get streaming audio? Thinking of a project where that would cut out a lot of the headache if it worked out of the box.