It's been ages since I posted anything on electronics, even though I keep playing to learn more. I also frequent dx.com quite a bit and a fun little thing I picked up was a $2 radio-curcuit-board. It's a fully programmable FM radio that is 11 x 11 x 4 mm in size. As usual with electronics from China, the website barely says anything about the product. You just have to buy one and see if you can make it work.
The circuit came without any documentation, but Google is your best friend. The datasheet was all in Chinese, but thanks to Google Translate I figured out that this circuit was very similar to many other implementations of the TEA5767 radio chip. These chips all have the same pin-density as ZigBee modules, so I soldered on some ZigBee-headers to make connecting it easier. As you can see from the picture above, my cables were all over the place. Below is a cleaned up sketch of how to connect the TEA5767 radio module from dx.com (click to view full size). The audio amp obviously goes in between the speaker and the TEA5767 output.
The TEA5767 can be controlled using either Serial or I2C, so it's really flexible. It's not very powerful, so you'll need an audio amplifier to hear anything. I used an Adafruit MAX98306 amp breakout that I had from a former project. I won't get any style-points for this setup, but I'm glad I got it to work almost right away. This instructable made the code part really easy. Using a 10k pot to control the frequency also highlighted that more than 10-bit resolution would be nice (for better precision) or maybe one should rather use an encoder? Good learning fun anyway. Here's a vid of it working.
07 January 2013 at 5:45 pm