More ESP8266 projects, radio and epaper

Saturday, 6 January 2018

I finally got the radio-project I've been talking about for the past while working. To recap:

  • I started with an RDA5807M module, but that was too small, and too badly-performing.
  • I moved on to using an Si4703-based integrated "evaluation" board. That was fine for headphones, but little else.
  • I finally got a TEA5767-based integrated "evaluatioN" board, which works just fine.
    • Although it is missing RDS (the system that lets you pull the name of the station off the transmission).
    • It also has no (digital) volume-control, so you have to adjust the volume physically, like a savage.

The project works well, despite the limitations, so I have a small set of speakers and the radio wired up. I can control the station via my web-browser and have an alarm to make it turn on/off at different times of day - cheating at that by using the software-MUTE facility.

All in all I can say that when it comes to IoT the "S stands for Simplicity" given that I had to buy three different boards to get the damn thing working the way I wanted. That said total cost is in the region of €5, probably about the same price I could pay for a "normal" hand-held radio. Oops.

The writeup is here:

The second project I've been working on recently was controlling a piece of ePaper via an ESP8266 device. This started largely by accident as I discovered you can buy a piece of ePaper (400x300 pixels) for €25 which is just cheap enough that it's worth experimenting with.

I had the intention that I'd display the day's calendar upon it, weather forecast, etc. My initial vision was a dashboard-like view with borders, images, and text. I figured rather than messing around with some fancy code-based grid-layout I should instead just generate a single JPG/PNG on a remote host, then program the board to download and display it.

Unfortunately the ESP8266 device I'm using has so little RAM that decoding and displaying a JPG/PNG from a remote URL is hard. Too hard. In the end I had to drop the use of SSL, and simplify the problem to get a working solution.

I wrote a perl script (what else?) to take an arbitrary JPG/PNG/image of the correct dimensions and process it row-by-row. It would keep track of the number of contiguous white/black pixels and output a series of "draw Lines" statements.

The ESP8266 downloads this simple data-file, and draws each line one at a time, ultimately displaying the image whilst keeping some memory free.

I documented the hell out of my setup here:

And here is a sample image being displayed:



Comments On This Entry

[gravitar] Tim Kramer

Submitted at 00:52:07 on 9 january 2018

I've had all three of the FM receiver boards working while connected to RPi. I can provide my janky C code if you want it. Shouldn't be that difficult to port to the ESP8266 (each relies on a bit of binary math). The e-paper project looks interesting.

[author] Steve Kemp

Submitted at 05:54:01 on 9 january 2018

Thanks, but I think I'm good for code. My problems with the module were more to do with physical things.

(e.g. The first board being too damn small to solder easily, but then requiring an amplifier for even headphone output - obviously that is a problem that can easily be corrected, by adding it.)


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