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espressif,esp32-pinctrl
Vendor: Espressif Systems
Description
Espressif's Pin controller Node
Based on pincfg-node.yaml binding.
Espressif's pin controller is in charge of controlling pin configurations, pin
functionalities and pin properties as defined by pin states. In its turn, pin
states are composed of pre-defined pin muxing definitions and user-provided
pin properties.
Each Zephyr-based application has its own set of pin muxing/pin configuration
requirements. The next steps use ESP-WROVER-KIT's I2C_0 to illustrate how one
could change a node's pin state properties. Though based on a particular board,
the same steps can be tweaked to address specifics of any other target board.
Suppose an application running on top of the ESP-WROVER-KIT board, for some
reason it needs I2C_0's SDA signal to be routed to GPIO_33. When looking at
that board's original device tree source file (i.e., 'esp_wrover_kit.dts'),
you'll notice that the I2C_0 node is already assigned to a set of states.
Below is highlighted the information that most interests us on that file
#include "esp_wrover_kit-pinctrl.dtsi"
&i2c0 {
pinctrl-0 = <&i2c0_sda_gpio21 &i2c0_scl_gpio22>;
pinctrl-names = "default";
};
From the above excerpt, the pincrl-0 property is composed of 'i2c0_sda_gpio21'
and 'i2c0_scl_gpio22' pin states. The naming convention makes it clear that
I2C_0's SDA signal is, by default, routed to GPIO_21 on the target board. Pin
states are defined on another file (i.e, 'esp_wrover_kit-pinctrl.dtsi') on
the same folder of the DTS file. Check below the excerpt describing SDA's
pin state
i2c0_sda_gpio21: i2c0_sda_gpio21 {
pinmux = <I2C0_SDA_GPIO21>;
bias-pull-up;
drive-open-drain;
output-high;
};
Only the 'pinmux' property above is actually required, other properties can
be chosen if meaningful for the target application and, of course, supported
by your target hardware. For example, some custom board may have an external
pull-up resistor soldered to GPIO_21's pin pad, in which case, 'bias-pull-up'
could be no longer required.
Back to our fictional application, the previous SDA state definition does not
meet our expectations, remember, we would like to route I2C_0's SDA signal to
GPIO_33 and not to GPIO_21. To achieve our goal, we need to update the 'pinmux'
property accordingly.
Note that replacing 'I2C0_SDA_GPIO21' by 'I2C0_SDA_GPIO33' is very tempting and
may even work, however, unless you have checked the hardware documentation first,
it is not recommended. That's because there are no guarantees that a particular
IO pin has the capability to route any specific signal.
The recommendation is to check the pinmux macros definitions available for the
target SoC in the following URL
https://github.com/zephyrproject-rtos/hal_espressif/tree/zephyr/include/dt-bindings/pinctrl
The ESP-WROVER-KIT board is based on the ESP32 SoC, in that case, we search
through the file 'esp32-pinctrl.h' in the above URL. Luckily for us, there is
one definition on that file that corresponds to our needs
#define I2C0_SDA_GPIO33 \
ESP32_PINMUX(33, ESP_I2CEXT0_SDA_IN, ESP_I2CEXT0_SDA_OUT)
Now, we go back to edit 'esp_wrover_kit-pinctrl.dtsi' and create a new pin state
on that file (or replace/update the one already defined) using the pinmux macro
definition above, yielding
i2c0_sda_gpio33: i2c0_sda_gpio33 {
pinmux = <I2C0_SDA_GPIO33>;
bias-pull-up;
drive-open-drain;
output-high;
};
Finally, update the I2C0 node state information in the device tree source using the
new (or updated) state
&ic20 {
pinctrl-0 = <&i2c0_sda_gpio33 &i2c0_scl_gpio22>;
pinctrl-names = "default";
};
With proper adaptations, the same steps above apply when using different
combinations of boards, SoCs, peripherals and peripheral pins.
Note: Not all pins are available for a given peripheral, it depends if that
pin supports a set of properties required by the target peripheral.
When defining a state, the pin muxing information is constrained to
the definitions at 'hal_espressif', however, pin properties (like
bias-push-pull, drive-open-drain, etc) can be freely chosen, given the
property is meaningful to the peripheral signal and that it is also
available in the target GPIO.
Properties
Top level properties
These property descriptions apply to “espressif,esp32-pinctrl” nodes themselves. This page also describes child node properties in the following sections.
Properties not inherited from the base binding file.
(None)
Deprecated properties not inherited from the base binding file.
(None)
Properties inherited from the base binding file, which defines common properties that may be set on many nodes. Not all of these may apply to the “espressif,esp32-pinctrl” compatible.
Name |
Type |
Details |
|---|---|---|
|
|
register space
See Important properties for more information. |
|
|
indicates the operational status of a device
Legal values: See Important properties for more information. |
|
|
compatible strings
This property is required. See Important properties for more information. |
|
|
name of each register space
|
|
|
interrupts for device
See Important properties for more information. |
|
|
extended interrupt specifier for device
|
|
|
name of each interrupt
|
|
|
phandle to interrupt controller node
|
|
|
Human readable string describing the device (used as device_get_binding() argument)
See Important properties for more information. |
|
|
Clock gate information
|
|
|
name of each clock
|
|
|
number of address cells in reg property
|
|
|
number of size cells in reg property
|
|
|
DMA channels specifiers
|
|
|
Provided names of DMA channel specifiers
|
|
|
IO channels specifiers
|
|
|
Provided names of IO channel specifiers
|
|
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mailbox / IPM channels specifiers
|
|
|
Provided names of mailbox / IPM channel specifiers
|
|
|
Property to identify that a device can be used as wake up source.
When this property is provided a specific flag is set into the
device that tells the system that the device is capable of
wake up the system.
Wake up capable devices are disabled (interruptions will not wake up
the system) by default but they can be enabled at runtime if necessary.
|
|
|
Power domain the device belongs to.
The device will be notified when the power domain it belongs to is either
suspended or resumed.
|
Child node properties
Name |
Type |
Details |
|---|---|---|
|
|
Integer value, represents pin mux settings.
With:
- pin: The gpio pin number (0, 1, ..., GPIO_NUM_MAX)
- sigi: The input signal assigned to a pin, if not available, it gets
assigned to ESP_NOSIG
- sigo: The output signal assigned to a pin, if not available, it gets
assigned to ESP_NOSIG
To simplify the usage, macro is available to generate "pinmux" field.
This macro is available here:
-include/zephyr/dt-bindings/pinctrl/esp-pinctrl-common.h
Some examples of macro usage:
GPIO 3 set as UART0's RX pin
... {
pinmux = <ESP32_PINMUX(3, ESP_U0RXD_IN, ESP_NOSIG)>;
};
This property is required. |
|
|
disable any pin bias
|
|
|
enable pull-up resistor
|
|
|
enable pull-down resistor
|
|
|
drive actively high and low
|
|
|
drive with open drain (hardware AND)
|
|
|
enable input on pin (no effect on output, such as enabling an input
buffer)
|
|
|
enable output on a pin without actively driving it (such as enabling
an output buffer)
|
|
|
set the pin to output mode with low level
|
|
|
set the pin to output mode with high level
|