“With the portable Li-Ion battery powered FM radio receiver you can listen to your favourite radio station. This device is equipped with cost-effective components, including a CH32V003J4M6 32-bit RISC-V microcontroller, a RDA5807MP FM radio tuner IC, an audio amplifier (TC8871 or XPT8871), a 128x32 pixel OLED display (SSD1306), and a Li-Ion battery charger (TP4054 or MCP73831). You can directly connect a protected 3.7V LiPo battery, a 3W / 4Ω speaker, and an FM antenna. The FM Radio Receiver is a port from the ATtiny412 version.
The CH32V003 Family of 32-bit RISC-V Microcontrollers
The CH32V003 series is a collection of industrial-grade general-purpose microcontrollers that utilize the QingKe RISC-V2A core design supporting the RV32EC instruction set. These microcontrollers are equipped with various features such as a 48MHz system main frequency, 16KB flash, 2KB SRAM, wide voltage support, a single-wire serial debug interface, low power consumption, and an ultra-small package. Additionally, the CH32V003 series includes a built-in set of components including a DMA controller, a 10-bit ADC, op-amp comparators, multiple timers, and standard communication interfaces such as USART, I2C, and SPI.
RDA5807MP FM Radio Tuner IC
The low-cost RDA5807MP is a single-chip broadcast FM stereo radio tuner with fully integrated synthesizer, IF selectivity, RDS/RBDS, and MPX decoder. The tuner uses the CMOS process, support multi-interface, and require the least external component. All these make it very suitable for portable devices. The RDA5807MP is controlled by the microcontroller via I²C.
TC8871 Audio Amplifier IC
The TC8871 is an FM-free, Class AB/Class D selectable power amplifier. When the working voltage is 5V, the maximum driving power is 5W (2Ω, BTL load, THD>10%). The application circuit of TC8871 is simple, only a few peripheral devices are needed, and the feedback resistor is integrated; the output does not need an external coupling capacitor or a power-up capacity and buffer network. The amplification can be selected via the value of the resistors R3 and R4 (Gain = 2 * 100kΩ / (10kΩ + R3), R4 respectively), which determines the maximum volume. Keep in mind that the resistors together with the coupling capacitors C3 and C4 form a high-pass filter whose cut-off frequency is determined using the following formula: f = 1 / (2 * π * R3 * C3), R4 and C4 respectively.
TP4054 Li-Ion Battery Charge IC
For battery charging the TP4054 is used. The TP4054 is a complete constant-current/constant-voltage linear charger for single cell lithium-ion batteries. Its small package and low external component count make the TP4054 ideally suited for portable applications. The constant current value is set with one external resistor (I = 1000V / R6). Charging is done via the built-in USB-C connector. The TP4054 can be replaced by a MCP73831.
ME6209A33 3.3V Linear Voltage Regulator
The ME6209 series are a group of positive voltage output, three–pin regulator, that provide a high current (max 250mA) even when the input/output voltage differential is small (80mV dropout voltage). Low power consumption (3µA quiescent current) and high accuracy (+/-2%) is achieved through CMOS technology. They allow input voltages as high as 18V.”