My Raspberry Pi based Internet Radio/Weather Station is going to get a new feature soon - an FM transmitter. You can buy a discontinued Sony Ericsson MMR-70 FM Transmitter for less than 2 EUR now and it can be connected to Raspberry Pi quite easily. Tobias Mädel has done excellent work putting together a small FMBerry daemon which can control MMR-70 connected to RPi's I2C bus. In this case Raspberri Pi is connected directly to I2C pins on Alps TSMZ1-603A FM transmitter (built on NS741 low power FM transmitter chip). Onboard Atmega 32-M is not used and forced to a sleep state to avoid any control conflicts.
MMR-70 has an LED, but it's connected to Mega32 pin 16, so a bit of high precision soldering is required :) To control the LED we need to solder wire directly to the LED or close to Mega32 pin 16:
MMR-70 has an LED, but it's connected to Mega32 pin 16, so a bit of high precision soldering is required :) To control the LED we need to solder wire directly to the LED or close to Mega32 pin 16: