Transmit your custom audio across FM band with PiFmAdv
It works by using GPIO4(pin 7) which is the oscillator pin, which is used to send an RF signal.
sudo ./pi_fm_adv --freq 87.5 --audio sound.wav
Then use a radio and tune to 87.5Mhz FM and you should hear the wav file. I was chuffed when I got this to work.
Use an ADC to access analog devices with raspberry pi
Bought a MCP3008. The great thing about this ADC is that there is direct linux support for it. Enable SPI(dtparam=spi=on in /boot/config.txt or via raspi-config), make a change to /boot/config.txt (dtoverlay=mcp3008:spi0-0-present ) to load drivers at boot, then access the raw values by simply accessing a virtual file on the filesystem (cat /sys/bus/iio/devices/iio:device0/in_voltage0_raw ). Nifty.
Backup and restore unknown Arduino program with Raspberry Pi