Encoder_EQEP

Description

C interface for the Sitara eQEP encoder counter.

<rc/encoder_eqep.h>

Functions for reading the eQEP hardware-accelerated quadrature encoder counters. This can be used for reading encoder channels 1-3 on the Robotics Cape and BeagleBone Blue. Channel 4 is counted with the PRU, see <rc/encoder_pru.h> to use the 4th channel.

Author

James Strawson

Date

1/31/2018

Functions
int	rc_encoder_eqep_init (void)
	Initializes the eQEP encoder counters for channels 1-3. More...
int	rc_encoder_eqep_cleanup (void)
	Stops the eQEP 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_eqep_read (int ch)
	Reads the current position of an encoder channel. More...
int	rc_encoder_eqep_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_eqep_init()

int rc_encoder_eqep_init

(

void

)

Initializes the eQEP encoder counters for channels 1-3.

This also resets the encoder position to 0 so the first position read is consistent. Note this does NOT initialize the PRU-accelerated encoder counter on channel 4. To use the 4th channel you must use <rc/encoder_pru.h>

Returns

0 on success or -1 on failure

Examples:

rc_balance.c, and rc_test_encoders_eqep.c.

rc_encoder_eqep_cleanup()

int rc_encoder_eqep_cleanup

(

void

)

Stops the eQEP 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_balance.c, and rc_test_encoders_eqep.c.

rc_encoder_eqep_read()

int rc_encoder_eqep_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 1-3

Returns

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

Examples:

rc_balance.c, and rc_test_encoders_eqep.c.

rc_encoder_eqep_write()

int rc_encoder_eqep_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 1-3
[in]	pos	The new position

Returns

0 on success, -1 on failure

Examples:

rc_balance.c.