Note: This step is only necessary, if you use a Raspberry Pi 3.

The biggest change of Raspberry Pi 3 was the integrated WLAN and Bluetooth. But the Bluetooth module uses the serial (UART) interface of the Pi. So after activating the serial interface with raspi-config, there only a Mini-UART available over the GPIO pins. The Mini-UART has a big disatvantage: the baudrate of the Mini-UART depends of the Clock-Speed of the CPU, so a stable serial connection is not possible. You can change that by disabling the Bluetooth module and reconfigure the UART to the GPIO pins.

Open the "config.txt" at the boot directory with admin privilege.

sudo nano /boot/config.txt

Add a new line with dtoverlay=pi3-disable-bt and if it is not set by raspi-config, add a line with enable_uart=1 [2]. Now open the file:

sudo nano /boot/cmdline.txt

Delete the part with console=serial0,115200 [3]. Now you need to stop BT modem trying to use UART:

sudo systemctl disable hciuart

After a reboot, the UART should work like at the previous Raspberry Pi version. The UART is available under "/dev/ttyAMA0".

pip3 list

pip3 install <module-name>

sudo pigpiod

sudo nano /etc/rc.local

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

# Print the IP address
_IP=$(hostname -I) || true
if [ "$_IP" ]; then
  printf "My IP address is %s\n" "$_IP"
fi

pigpiod

exit 0