AxiGPIO

The AxiGPIO class provides methods to read, write, and receive interrupts from external general purpose peripherals such as LEDs, buttons, switches connected to the PL using AXI GPIO controller IP.

Block Diagram

The AxiGPIO module controls instances of the AXI GPIO controller in the PL. Each AXI GPIO can have up to two channels each with up to 32 pins.

The read() and write() methods are used to read and write data on a channel (all of the GPIO).

setdirection() and setlength() can be used to configure the IP. The direction can be ‘in’, ‘out’, and ‘inout’.

By default the direction is ‘inout’. Specifying ‘in’ or ‘out’ will only allow read and writes to the IP respectively, and trying to read an ‘out’ or write an ‘in’ will cause an error.

The length can be set to only write a smaller range of the GPIO.

The GPIO can also be treated like an array. This allows specific bits to be set, and avoids the need to use a bit mask.

The interrupt signal, ip2intc_irpt from the AXI GPIO can be connected directly to an AXI interrupt controller to cause interrupts in the PS. More information about AsyncIO and Interrupts can be found in the PYNQ and Asyncio section.

The LED, Switch, Button and RGBLED classes extend the AxiGPIO controller and are customized for the corresponding peripherals. These classes expect an AXI GPIO instance called [led|switch|button|rgbleds]_gpio to exist in the overlay used with this class.

Examples

This example is for illustration, to show how to use the AxiGPIO class. In practice, the LED, Button, Switches, and RGBLED classes may be available to extend the AxiGPIO class should be used for these peripherals in an overlay.

After an overlay has been loaded, an AxiGPIO instance can be instantiated by passing the name of the AXI GPIO controller to the class.

from pynq import Overlay
from pynq.lib import AxiGPIO
ol = Overlay("base.bit")

led_ip = ol.ip_dict['gpio_leds']
switches_ip = ol.ip_dict['gpio_switches']
leds = AxiGPIO(led_ip).channel1
switches = AxiGPIO(switches_ip).channel1

Simple read and writes:

mask = 0xffffffff
leds.write(0xf, mask)
switches.read()

Using AXI GPIO as an array:

switches.setdirection("in")
switches.setlength(3)
switches.read()

More information about the AxiGPIO module and the API for reading, writing and waiting for interrupts can be found in the pynq.lib.axigpio Module sections.

For more examples see the “Buttons and LEDs demonstration” notebook for the PYNQ-Z1/PYNQ-Z2 board at:

<Jupyter Home>/base/board/board_btns_leds.ipynb

The same notebook may be found in the corresponding folder in the GitHub repository.