pinctrl is a more powerful replacement for raspi-gpio, a tool for displaying and modifying the GPIO and pin muxing state of a system. It accesses the hardware directly, bypassing the kernel drivers, and as such requires the necessary privilege. By default, root access is required (i.e. run with "sudo"), but with a suitable udev rule to change the ownership of /dev/gpiomem* (as found in RPiOS) this can be relaxed to group membership, e.g. group "gpio".

The improvements over raspi-gpio include:

• GPIO controllers are detected at runtime from Device Tree.
• GPIOs can be referred to by name or number.
• Pin mode (-p) switches the UI to be in terms of 40-way header pin numbers.
• The "poll" command causes it to constantly monitor the specified pins, displaying any level changes it sees. For slow signals (up to a few hundred kHz) it can act as a basic logic analyser.
• The "get" and "set" keywords are optional in most cases.
• Splitting into a general gpiolib library and a separate client application allows new applications to be added easily.

Documentation for gpiolib is provided here.

Build Instructions

Install the prerequisites with "sudo apt install cmake" - you need at least version 3.10 of cmake. Run the following commands, either here or in the top-level directory to build and install everything:

• cmake . N.B. Use cmake -DBUILD_SHARED_LIBS=1 . to build gpiolib as a shared (as opposed to static) library.
• make
• sudo make install

Usage

• sudo pinctrl (Display the state of all recognised GPIOs)
• sudo pinctrl -p (Show the state of the 40-way header pins)
• sudo pinctrl -l (List the recognised GPIO controllers)
• sudo pinctrl 4,6 op dl (Make GPIOs 4 and 6 outputs, driving low)
• sudo pinctrl poll BT_CTS,BT_RTS (Monitor the levels of the Bluetooth flow control signals)
• pinctrl funcs 9-11 (List the available alternate functions on GPIOs 9, 10 and 11)
• pinctrl help (Show the full usage guide)