- LIN - this is the line level LEFT input. Its connected to the headphone jack as well but in case you want to wire directly without a chunky cable, pipe line level (~0.7 Vpp) audio into here. There's an AC blocking capacitor on board so it can be DC biased
- RIN - same as LIN but the RIGHT input.
- Vin - this is the power input pin. You can power the chip from 3-5VDC. Ideally you should use the same voltage you use for logic levels. For an Arduino, that's usually 5V
- GND - this is power and logic ground, connect to your microcontroller's ground pin
3Vo - this is the output from the onboard regulator, 3.3V nominal. You can use this if you need up to 100mA of 3V regulated voltage
The FM transmitter chip requires a microcontroller for setting it up unlike pure-analog solutions that have a tuning potentiometer. The trade off is some code is needed, but the output is digitally tuned so its much more precise.
Our codebase uses I2C to communicate. The chip supports SPI as well but it was annoying enough to support just I2C so we don't have code examples for SPI!
All the interface input pins are 5V friendly, and can be used with 3-5V logic
- RST - This is the Reset pin. You must have this pin toggle before starting to communicate with the chip. When at logic 0, the chip is in reset.
- CS - This is the Chip select pin, used in SPI mode. It also determines the I2C address. When pulled high (it is by default) the I2C address is 0x63. If this pin is shorted to ground, the I2C address is 0x11
- SCL - this is the I2C clock pin, connect to SCL on your microcontroller.
- SDA - this is the I2C data pin, connect to SDA on your microcontroller.
There's also two "GPIO" pins, you can use these to blink LEDs. The initial state of these pin sets up the chip for Analog Mode so don't short them to ground or VCC during reset. They are 3V output only!
- GP1 - this is GPIO #1
- GP2 - this is GPIO #2