#rda5807m

This project focuses on a simple yet powerful FM stereo tuner module. The core component of the module is RDA5807M, a single-chip broadcast FM stereo tuner that has gained popularity among designers in recent years due to its high level of integration. This integration significantly reduces the need for external components, simplifying circuit design. The RDA5807M supports a wide FM band, covering frequencies from 50MHz to 115MHz, making it adaptable to global FM standards.

Additionally, its use of a low-IF digital architecture streamlines the design process by requiring fewer external parts. The inclusion of an AGC (automatic gain control) feature ensures consistent signal reception, even in environments with fluctuating signal strengths.

The chip's digital stereo decoding capabilities deliver high-quality audio output, providing a rich stereo sound experience. Moreover, the energy efficiency of the RDA5807M makes it suitable for portable, battery-powered devices. The I2C control interface allows for easy integration with microcontrollers, enabling straightforward digital control.

This module is designed as a ready-to-use FM receiver solution, emphasizing compactness and ease of integration. It incorporates the RDA5807M IC and the STM8S003F3P MCU, along with the necessary supporting passive components, standard headers for connections, and flexible antenna connectivity options. The module is engineered to connect with commonly available 0.56-inch, 4-digit common cathode LED seven-segment display modules without any soldering.

The compact footprint of the module makes it ideal for projects where space is at a premium. Importantly, its open-source design allows for complete customization and modification.

It provides standard stereo audio output with separate left and right channels. The antenna input options allow for various antenna types, ensuring optimal signal reception. During testing, we utilized a 30cm long wire as the antenna and successfully received all FM stations clearly.

The tuner module features push switches to perform automatic station scans in both directions. The firmware limits the tuning range of the module to between 87MHz and 108MHz. Additionally, it includes digital volume control with 15 levels and a memory manager for storing up to 10 FM radio stations. The current tuner frequency is displayed on the segment display module, and there are two LEDs to indicate stereo reception and memory manager status.

The output level of this receiver module is not sufficient to drive speakers directly. Therefore, to achieve audio output through speakers, this module needs to be paired with a stereo audio amplifier. During testing, we successfully used the commonly available PAM8403 3W class-D audio amplifier with this module.

Power is supplied via a screw terminal, typically requiring a DC power source between 5V and 9V. The dimensions of the module are 72.85mm × 32.0mm.

FM stereo tuner using RDA5807M ( RRD-102 V2.0 )

Sound : ***** (five stars) ….. Fine tuned !!!

This is an RDA5807M based FM stereo radio module. This module is designed to replace old, low-voltage, analog FM stereo radio receiver modules. Like many digital receivers, this module also got auto scanning, station memory, and digital volume control. This module can driver using 5V to 9V DC power source.

The frequency range of the receiver is 88MHz to 108MHz. The auto scanner of this module can tune the receiver with 25kHz increments in up and down directions. The memory manager available with the current firmware can hold up to 10 stations in MCU EEPROM. 

The dimensions of this module are 72.85mm × 32.0mm. With the seven-segment display, the depth of the assembled module is 37.5mm.

AF output power of this module is not sufficient to handle the pair of speakers. To drive speakers, this module needs to pair with a stereo AF power amplifier kit/module.

This tuner circuit is a quick prototype which I build to test the RDA5807M FM radio tuner IC. RDA5807M is a single-chip tuner IC with RDS and MPX decoder, and it equipped with I2C interface for control. The main reason to build this prototype is to understand the behavior of this chip.

At the time of this design, the website of the RDA microelectronics is not accessible from my location. Because of this reason, I download different versions of RDA5807M datasheets from the internet. While going-through those datasheets, I observed that it comes with limited information. Finally, I decided to build this receiver to verify some of those parameters and to review the RDS functionality of the chip.

I build this receiver around ATmega16A MCU. I choose this MCU because I got a few of ATmega16A MCUs in my inventory and also due to the higher number of  I/O pin count.

In this design, the volume is controlled using M62429 IC. For the output stage, I used AN7147N, 2×5.3W audio power amplifier IC.

Based on the specifications of the switching-regulator and power amplifier, this circuit can drive between 9V to 20V DC input. At prototyping stages, we power this circuit using a 12V - 2.5A power supply unit.

The main problem which I encounter with this project is its PCB design. At prototyping stages, I did a couple of PCB designs to avoid interference and distortions. It seems like RDA5807M and AN7147N are sensitive to noise and need a proper PCB layout. In this final design, I got excellent results, and it performs better than I expected.

At the testing stages, this receiver decodes RDS signals from all the FM station including weak stations. "RanOne FM" is the most attractive station name which I captured from this receiver. This station transmits its name in an animated style and its display on the receiver's LCD without any problems.

The firmware of this receiver is developed using two verification buffers to avoid RDS decode errors. This technique helps to filter garbage data received due to poor reception.

The current version of the firmware supports both manual and auto-tuning functionalities with 100kHz spacing and, it is set to operate within 87MHz to 108MHz range.