GPIO Configuration (0x0C,0x41)

Description

Configures the user GPIO pins on the connector for use with several built-in functions or for general input or output.

Notes

GPIO pins are device-dependent. Some features are only available on certain pins. Some behaviors require specific configurations. Consult the device user manual for restrictions and default settings.

To avoid glitches on GPIOs configured as an output in a mode other than GPIO, always configure the relevant function before setting up the pin with this command. Otherwise, the pin state will be undefined between this command and the one to set up the feature. For input pins, use this command first so the state is well-defined when the feature is initialized.

Some configurations can only be active on one pin at a time. If such configuration is applied to a second pin, the second one will take precedence and the original pin's configuration will be reset.

Parameter Name Data Type Description

Field Length u8 7

Descriptor u8 0x41

Function Selector u8 This command supports the following MIP function selectors:
Write Read Save Load Default [WRSLD]

Pin [WRSLD] u8 GPIO pin number counting from 1. For save, load, and default function selectors, this can be 0 to select all pins.

Feature

[W]

u8 enum

Determines how the pin will be used.

Name	Value	Description
UNUSED	0	The pin is not used. It may be technically possible to read the pin state in this mode, but this is not guaranteed to be true of all devices or pins.
GPIO	1	General purpose input or output. Use this for direct control of pin output state or to stream the state of the pin.
PPS	2	Pulse per second input or output.
ENCODER	3	Motor encoder/odometer input.
TIMESTAMP	4	Precision Timestamping. Use with Event Trigger Configuration (0x0C,0x2E).
UART	5	UART data or control lines.

Behavior

[W]

u8 enum

Select an appropriate value from the enumeration based on the selected feature (e.g. for PPS, select one of the values prefixed with PPS_.)

Name	Value	Description
UNUSED	0	Use 0 unless otherwise specified.
GPIO_INPUT	1	Pin will be an input. This can be used to stream or poll the value and is the default setting.
GPIO_OUTPUT_LOW	2	Pin is an output initially in the LOW state. This state will be restored during system startup if the configuration is saved.
GPIO_OUTPUT_HIGH	3	Pin is an output initially in the HIGH state. This state will be restored during system startup if the configuration is saved.
PPS_INPUT	1	Pin will receive the pulse-per-second signal. Only one pin can have this behavior. This will only work if the PPS Source command is configured to GPIO.
PPS_OUTPUT	2	Pin will transmit the pulse-per-second signal from the device.
ENCODER_A	1	Encoder "A" quadrature input. Only one pin can have this behavior. The last command to set this behavior will take precedence.
ENCODER_B	2	Encoder "B" quadrature input. Only one pin can have this behavior. The last command to set this behavior will take precedence.
TIMESTAMP_RISING	1	Rising edges will be timestamped.
TIMESTAMP_FALLING	2	Falling edges will be timestamped.
TIMESTAMP_EITHER	3	Both rising and falling edges will be timestamped.
UART_PORT2_TX	33	(0x21) UART port 2 transmit.
UART_PORT2_RX	34	(0x22) UART port 2 receive.
UART_PORT3_TX	49	(0x31) UART port 3 transmit.
UART_PORT3_RX	50	(0x32) UART port 3 receive.

Pin Mode

[W]

u8 bitfield

GPIO configuration. May be restricted depending on device, pin, feature, and behavior. See device user manual.

Name	Bit(s)	Description
open_drain	0	The pin will be an open-drain output. The state will be either LOW or FLOATING instead of LOW or HIGH, respectively. This is used to connect multiple open-drain outputs from several devices. An internal or external pull-up resistor is typically used in combination. The maximum voltage of an open drain output is subject to the device maximum input voltage range found in the specifications.
pulldown	1	The pin will have an internal pull-down resistor enabled. This is useful for connecting inputs to signals which can only be pulled high such as mechanical switches. Cannot be used in combination with pull-up. See the device specifications for the resistance value.
pullup	2	The pin will have an internal pull-up resistor enabled. Useful for connecting inputs to signals which can only be pulled low such as mechanical switches, or in combination with an open drain output. Cannot be used in combination with pull-down. See the device specifications for the resistance value. Use of this mode may restrict the maximum allowed input voltage. See the device datasheet for details.

Ack/Nack Reply See standard MIP ack/nack reply format.

Response Data Data Type Description

Response Length u8 6

Response Descriptor u8 0xC1

Pin u8 GPIO pin number counting from 1. For save, load, and default function selectors, this can be 0 to select all pins.

Feature

u8 enum

Determines how the pin will be used.

Name	Value	Description
UNUSED	0	The pin is not used. It may be technically possible to read the pin state in this mode, but this is not guaranteed to be true of all devices or pins.
GPIO	1	General purpose input or output. Use this for direct control of pin output state or to stream the state of the pin.
PPS	2	Pulse per second input or output.
ENCODER	3	Motor encoder/odometer input.
TIMESTAMP	4	Precision Timestamping. Use with Event Trigger Configuration (0x0C,0x2E).
UART	5	UART data or control lines.

Behavior

u8 enum

Select an appropriate value from the enumeration based on the selected feature (e.g. for PPS, select one of the values prefixed with PPS_.)

Name	Value	Description
UNUSED	0	Use 0 unless otherwise specified.
GPIO_INPUT	1	Pin will be an input. This can be used to stream or poll the value and is the default setting.
GPIO_OUTPUT_LOW	2	Pin is an output initially in the LOW state. This state will be restored during system startup if the configuration is saved.
GPIO_OUTPUT_HIGH	3	Pin is an output initially in the HIGH state. This state will be restored during system startup if the configuration is saved.
PPS_INPUT	1	Pin will receive the pulse-per-second signal. Only one pin can have this behavior. This will only work if the PPS Source command is configured to GPIO.
PPS_OUTPUT	2	Pin will transmit the pulse-per-second signal from the device.
ENCODER_A	1	Encoder "A" quadrature input. Only one pin can have this behavior. The last command to set this behavior will take precedence.
ENCODER_B	2	Encoder "B" quadrature input. Only one pin can have this behavior. The last command to set this behavior will take precedence.
TIMESTAMP_RISING	1	Rising edges will be timestamped.
TIMESTAMP_FALLING	2	Falling edges will be timestamped.
TIMESTAMP_EITHER	3	Both rising and falling edges will be timestamped.
UART_PORT2_TX	33	(0x21) UART port 2 transmit.
UART_PORT2_RX	34	(0x22) UART port 2 receive.
UART_PORT3_TX	49	(0x31) UART port 3 transmit.
UART_PORT3_RX	50	(0x32) UART port 3 receive.

Pin Mode

u8 bitfield

GPIO configuration. May be restricted depending on device, pin, feature, and behavior. See device user manual.

Name	Bit(s)	Description
open_drain	0	The pin will be an open-drain output. The state will be either LOW or FLOATING instead of LOW or HIGH, respectively. This is used to connect multiple open-drain outputs from several devices. An internal or external pull-up resistor is typically used in combination. The maximum voltage of an open drain output is subject to the device maximum input voltage range found in the specifications.
pulldown	1	The pin will have an internal pull-down resistor enabled. This is useful for connecting inputs to signals which can only be pulled high such as mechanical switches. Cannot be used in combination with pull-up. See the device specifications for the resistance value.
pullup	2	The pin will have an internal pull-up resistor enabled. Useful for connecting inputs to signals which can only be pulled low such as mechanical switches, or in combination with an open drain output. Cannot be used in combination with pull-down. See the device specifications for the resistance value. Use of this mode may restrict the maximum allowed input voltage. See the device datasheet for details.