Encoder

Description

C interface for quadrature encoder counting.

<rc/encoder.h>

Functions for reading the eQEP hardware-accelerated quadrature encoder counters and the PRU accelerated encoder counter.Channels 1-3 on the Robotics Cape and BeagleBone Blue are counted using the Sitara's eQEP counter. Channel 4 is counted with the PRU.

Author

James Strawson

Date

5/12/2018

Functions
int	rc_encoder_init (void)
	Initializes counters for channels 1-4. More...
int	rc_encoder_cleanup (void)
	Stops the encoder counters and closes file descriptors. This is not strictly necessary but is recommended that the user calls this function at the end of their program. More...
int	rc_encoder_read (int ch)
	Reads the current position of an encoder channel. More...
int	rc_encoder_write (int ch, int pos)
	Sets the current position of an eQEP encoder channel. Usually for resetting a counter to 0 but can set an arbitrary position if desired. More...

Function Documentation

rc_encoder_init()

int rc_encoder_init

(

void

)

Initializes counters for channels 1-4.

This also resets the encoder position to 0 so the first position read is consistent.

Returns

0 on success or -1 on failure

Examples:

rc_test_encoders.c.

rc_encoder_cleanup()

int rc_encoder_cleanup

(

void

)

Stops the encoder counters and closes file descriptors. This is not strictly necessary but is recommended that the user calls this function at the end of their program.

Returns

0 on success or -1 on failure.

Examples:

rc_test_encoders.c.

rc_encoder_read()

int rc_encoder_read

(

int

ch

)

Reads the current position of an encoder channel.

This is a signed 32-bit integer that wraps around if the position is allowed to read +- 2^31

Parameters

[in]

ch

channel 1-4

Returns

The current position (signed 32-bit integer) or -1 and prints an error message is there is a problem.

Examples:

rc_test_encoders.c.

rc_encoder_write()

int rc_encoder_write	(	int	ch,
		int	pos
	)

Sets the current position of an eQEP encoder channel. Usually for resetting a counter to 0 but can set an arbitrary position if desired.

Parameters

[in]	ch	channel 1-4
[in]	pos	The new position

Returns

0 on success, -1 on failure