# Sixth Lichuang Electric Competition #DIY Radio Amplifier

* 1. Introduction to project functions

The DIY radio based on PAM8403, RDA5807, and STM32F030F4 chips can drive 3W speakers and supports two-channel volume output. The radio supports frequencies from 87Mhz to 108Mhz.

*2. Project attributes

for listening to radio

* 3. Open source agreement

GPL3.0 open source agreement

*4. Hardware part

1.FM frequency modulation chip:

The domestic chip RDA5807 was used, and the verification was successful based on the schematic diagram drawn based on the application circuit in the data sheet. The RDA5807 chip communicates with the MCU using the IIC protocol. There are ten registers inside the chip.

Note: L1 and L2 are 100Mhz magnetic beads

2. Power amplifier chip:

The power amplifier chip uses PAM8403. Considering that the volume of the radio cannot be too high, a 4 ohm 3W speaker is chosen. With PAM8403, the full output can be achieved.
3. Display part:

The digital tube driver chip TM1620 drives the 0.56-inch common cathode digital tube. The MCU on the board is STM32F030F4, which controls the digital tube driver chip TM1620 and the FM frequency modulation chip RDA5807. 4. Antenna part:

Two interfaces are drawn on the antenna part. The upper interface is an IPEX interface, and the lower interface is a 3.5M interface, which can be used to plug in antennas or headphones with a wire length greater than 20CM. The longer the length of the antenna, the better the FM modulation effect. You can also weld a copper wire longer than 20cm on the left side of R5 to serve as an antenna.

5. Software description

1. After power on, the default is 87.0Mhz and the volume is 4. The volume can be adjusted up to 16 levels.

2. Press button 1 to decrease 0.1Mhz, and button 2 to increase 0.1Mhz. If you press and hold the button for more than 1 second, it will increase and decrease rapidly.

3. Quickly double-click button 1, and the digital tube will enter the volume setting interface. Press button 1 to decrease the level by 1, and press button 2 to increase the level by 1. Quickly double-click button 1 again to return to the FM setting interface.

6. Demonstration video