An industrious maker has built a pocket-sized FM radio, based on an ATtiny Microcontroller. Many people of a certain age will remember that AM/FM radio was one of the very few forms of audio playback available to them. That was before the MP3, the USB Drive, Streaming, or even the Internet allowed us to listen to music in a myriad of ways.
The pocket radio is about as small as it could be, with an ATtiny 402/412 as its core. There is also an integrated circuit FM tuner, an integrated audio amplifier with a small speaker, and a compact OLED display. The unit is backed up by a lithium-polymer battery charger and an analog user interface of three buttons. The buttons control the browsing of radio stations and controlling volume.
The entire build with speaker and control deck fits neatly in the palm of the hand or the back pocket of your khakis. It is a fully functional build with a great deal of mobility and ability for an FM receiver of this size.
Quick Specifications
- RDA5807MP FM Radio Tuner IC
- Controlled by an ATtiny 412 via I2C
- TC8871 Audio Amplifier IC
- MCP73831 Li-Ion Battery Charger IC
- ME6209 Voltage Regulator
Controlling the RDA5807
The FM tuner IC is an RDA5807MP and is controlled by I2C by the ATtiny. There are six writable 16-bit registers and six readable 16-bit registers. When writing to the RDA5807 the user can is either of two methods, a sequential write access method or an indexed method.
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- Sequential Method in accessed when the registers are always written starting from 0x02 address
- Indexed Method when the register address is transferred first and then the content.
Both methods are determined by differing I2C addresses. The transferring of the 16-bit registers needs the high-byte sent first. The RDA5807’s main control is by the setting or clearing of certain bits in respective registers. The data sheet has all the different details and meanings for the different registers. At GitHub, all the current register arrays are saved in the RDA_regs arrays
For further information see the GitHub ATtiny Pocket Radio Page
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For the past 8 years, I have been writing about embedded technologies, added to my technical, academic, and medical editorial experience, with companies like Elsevier and Cambridge University Press. I tell people to read what I write, not try to pronounce my last name. I am always available for comments and suggestions you can reach me at product-editor@circuitcellar.com and I promise I will take the time to reach back out to you. I live in the North East with my wonderful family.
