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[参考译文] AM6442：AM64X 中是否有适用于 eQEP 外设的 Linux (A53)驱动程序
EQEP
---------------------------------
.. rubric:: Introduction
:name: introduction-linux-eqep
Linux has support for EQEP (enhanced Quadature Encoder Pulse).
EQEP channels can be used to interface with rotary encoder hardware.
#. AM62x SK: EQEP0: k3-am62x-sk-eqep.dtso
#. AM62Ax SK: EQEP0: k3-am62x-sk-eqep.dtbo
#. AM64x SK: EQEP0: k3-am642-sk.dts
#. AM62p SK: EQEP0: k3-am62p5-sk-eqep.dtso
|
.. rubric:: Kernel Configuration
:name: driver-configuration-eqep
.. rubric:: Enable the eHRPWM driver
:name: enable-the-eqep-driver
.. code-block:: console
Device Drivers --->
<M> Counter support --->
<M> TI eQEP counter driver
.. note::
EQEP driver should be enabled by default as a module in TI Linux kernel.
|
.. rubric:: Driver Usage
:name: driver-usage-eqep
.. rubric:: Using EQEP with the sysfs interface
:name: using-eqep-with-sysfs-interface
Several sysfs attributes are generated by the Generic Counter interface, and reside under the
/sys/bus/counter/devices/counterX directory, where X is to the respective counter device id.
Please see Documentation/ABI/testing/sysfs-bus-counter for detailed information on each Generic
Counter interface sysfs attribute.
Through these sysfs attributes, programs and scripts may interact with the Generic Counter paradigm
Counts, Signals, and Synapses of respective counter devices.
- **Example**
.. code-block:: console
root@am62xx-evm:/sys/bus/counter/devices/counter0/count0# echo 0xff > ceiling
root@am62xx-evm:/sys/bus/counter/devices/counter0/count0# cat ceiling
255
root@am62xx-evm:/sys/bus/counter/devices/counter0/count0# echo 1 > enable
root@am62xx-evm:/sys/bus/counter/devices/counter0/count0# cat count
|
**Character device nodes**
Counter character device nodes are created under the /dev directory as counterX, where X is the respective counter device id.
.. code-block:: console
$ ls /dev/counter*
/dev/counter0
**Counter Events**
Please read the Generic counter API doc to implement events:
- docs.kernel.org/.../generic-counter.html
EQEP
----
.. rubric:: Introduction
:name: introduction-linux-eqep
Linux has support for EQEP (Enhanced Quadature Encoder Pulse).
EQEP channels can be used to interface with rotary encoder hardware.
.. ifconfig:: CONFIG_part_variant in ('AM62X', 'AM62AX')
- AM62x SK: EQEP0: k3-am62x-sk-eqep.dtso
.. ifconfig:: CONFIG_part_variant in ('AM64X')
- AM64x SK: EQEP0: k3-am642-sk.dts
.. ifconfig:: CONFIG_part_variant in ('AM62PX')
- AM62p SK: EQEP0: k3-am62p5-sk-eqep.dtso
.. rubric:: Kernel Configuration
:name: driver-configuration-eqep
Using menuconfig, enable the following driver:
.. code-block:: console
Device Drivers --->
<M> Counter support --->
<M> TI eQEP counter driver
.. note::
EQEP driver should be enabled by default as a kernel module in TI Linux kernel.
.. rubric:: Features supported in TI SDK
:name: features-supported-eqep
- position
- overflow/underflow events
- direction
- unit timer
- latched position
- edge capture
.. rubric:: Using eQEP with SYSFS interface
:name: sysfs-interface-eqep
Several sysfs attributes are generated by the Generic Counter interface, and reside under
the :file:`/sys/bus/counter/devices/counterX` directory, where X is to the respective counter
device id.
Please see the counter sysfs documentation `upstream <www.kernel.org/.../sysfs-bus-counter>`__
or in TI Linux kernel :file:`/Documentation/ABI/testing/sysfs-bus-counter` for detailed information on each
generic counter interface sysfs attribute.
Through these sysfs attributes, programs and scripts may interact with the Generic Counter paradigm
Counts, Signals, and Synapses of respective counter devices.
The following sysfs atributes can be found in :file:`/sys/bus/counter/devices/counterX` in TI SDK:
- countY/ceiling
- countY/count
- countY/direction
- countY/enable
- countY/function
- countY/latched_count
- countY/signal0_action
- countY/signal1_action
- edge_capture_unit_enable
- edge_capture_unit_latched_period
- edge_capture_unit_max_period
- edge_capture_unit_prescaler
- latch_mode
- unit_timer_enable
- unit_timer_period
- unit_timer_time
.. rubric:: Character device nodes
:name: character-device-nodes-eqep
Counter character device nodes are created under the /dev directory as counterX, where X is the respective counter device id.
.. code-block:: console
$ ls /dev/counter*
/dev/counter0
.. rubric:: Counter Events
:name: counter-events
Please read the generic counter API `upstream <docs.kernel.org/.../generic-counter.html>`__ or in
TI Linux kernel :file:`/Documentation/driver-api/generic-counter.rst` documentation to implement events:
.. rubric:: Test eQEP on AM62x SK
:name: test-eqep-am62x
+------------------------------------------+---------------------------------------------------------+
| .. Image:: /images/am62x_sk_eqep.jpg | .. Image:: /images/am62x_sk_rotary_encoder_breakout.jpg |
| :width: 380px | :width: 380px |
| :align: center | :align: center |
+------------------------------------------+---------------------------------------------------------+
| AM62x SK & rotary encoder breakout board | Example Diligent rotary encoder breakout board |
+------------------------------------------+---------------------------------------------------------+
The example rotary encoder breakout board used in this example can be found `here <www.digikey.com/.../4090075.
The following is an example for testing eQEP using sysfs interface:
.. code-block:: console
root@am62xx-evm:~# echo 0xff > /sys/bus/counter/devices/counter0/count0/ceiling
root@am62xx-evm:~# cat /sys/bus/counter/devices/counter0/count0/ceiling
255
root@am62xx-evm:~# echo 1 > /sys/bus/counter/devices/counter0/count0/enable
root@am62xx-evm:~# cat /sys/bus/counter/devices/counter0/count0/count
0
root@am62xx-evm:~# cat /sys/bus/counter/devices/counter0/count0/count
92
root@am62xx-evm:~# cat /sys/bus/counter/devices/counter0/count0/count
148
root@am62xx-evm:~# cat /sys/bus/counter/devices/counter0/count0/count
188
root@am62xx-evm:~# cat /sys/bus/counter/devices/counter0/count0/count
252
root@am62xx-evm:~# cat /sys/bus/counter/devices/counter0/count0/count
12
Notice in this example that turning the rotary shaft encoder counterclockwise increases the count
until reaching the ceiling, then wraps around to zero and starts again. Also, turning the rotary
shaft encoder clockwise decreases the count.
