In the age of 'music streaming', terrestrial radio listening seems antiquated. In the absence of WLAN or mobile communications, however, it can be an alternative to stay connected to the world, at least while consuming. FM (UKW) transmission was first trial took place in Germany almost 100 years ago (1925). And actually FM was supposed to be discontinued in 2012, but this only became reality in the cable network. To the delight of motorists with conventional analogue radios. The current digital successor DAB+ (the previous, incompatible and not very successful DAB was discontinued) is at least visible on the market and there are a number of inexpensive DAB+ receivers under €30. I decided to try out a TechniSat TECHNIRADIO RDR:

The radio has all the important functions for digital reception in a handy housing. But what if you had a small, programmable FM/DAB+ module that you could use in your own projects? A new project is born…

By the way, I had my first DIY attempt with DAB+ in 2014 with a module (T2-L4A-8650C) from the Taiwanese company KeyStone Semiconductor. Here is the related thread in microcontroller.net (German).

In the hobby area, however, the selection is still very limited. In the pandemic year 2020 I could only find two modules:

• DAB/DAB+/FM Radio Shield for Arduino for ca. £60,-
• uGreen DAB Board for ca. 45,-€

What all of these receivers have in common is that they are based on an IC SI4684-A10 from the US company Skyworks Solutions Inc. (formerly Silicon Labs.) which is available for approx. 15,- € from few US distributors (e.g. https://www.mouser.de/ProductDetail/Skyworks-Solutions-Inc/SI4684-A10-GM?qs=p9T7GgSe1IFl%2FK1mJ61MOg%3D%3D&gclid=EAIaIQobChMI1__CnMqw-gIVRIKGCh0yTgV1EAAYASAAEgJJq_D_BwE ). The SI4684 is a single-chip FM/DAB/DAB+ radio receiver (Datasheet ).

In order to use the IC for your own projects, you would need the evaluation board, which also includes the necessary firmware CD. However, the price of over €500 leaves the maker a bit perplexed and therefore restless. Unfortunately, the firmware alone is not (anymore) available online. A good source of information is the Rundfunkforum (German).

A look at the receiver H/W revealed that the firmware resides in an external serial FLASH memory (typ. 25L16). Depending on whether it is in FM or DAB+ operation, a different part of it is loaded into the SI4684.

So there is a solution at hand. Simply read out the FLASH and copy it for your own use. The right tool can be obtained in the Far East for less than €10.