| From: |
| Julien Panis <jpanis-AT-baylibre.com> |
| To: |
| jic23-AT-kernel.org, robh+dt-AT-kernel.org, krzysztof.kozlowski+dt-AT-linaro.org |
| Subject: |
| [PATCH v1 0/2] ECAP support on TI AM62x SoC |
| Date: |
| Tue, 26 Jul 2022 09:25:51 +0200 |
| Message-ID: |
| <20220726072553.5136-1-jpanis@baylibre.com> |
| Cc: |
| lars-AT-metafoo.de, linux-iio-AT-vger.kernel.org, devicetree-AT-vger.kernel.org, linux-kernel-AT-vger.kernel.org, mranostay-AT-ti.com, Julien Panis <jpanis-AT-baylibre.com> |
| Archive-link: |
| Article |
The Enhanced Capture (ECAP) module can be used to timestamp events
detected on signal input pin. It can be used for time measurements
of pulse train signals.
ECAP module includes 4 timestamp capture registers. For all 4 sequenced
timestamp capture events (0->1->2->3->0->...), edge polarity (falling/rising
edge) can be selected. Moreover, input signal can be prescaled.
This driver leverages IIO subsystem to :
- select edge polarity for all 4 capture events (event mode)
- log both event index and timestamp for each capture event
Event polarity, event indexes, and timestamps give all the information
about the input pulse train. Further information can easily be computed :
period and/or duty cycle if frequency is constant, elapsed time between
pulses, etc...
Userspace commands :
cd /sys/devices/platform/bus@f0000/23120000.capture/iio\:device2/
# Configure/Enable data buffers
echo 1 > scan_elements/in_index_en
echo 1 > scan_elements/in_timestamp_en
echo 100 > buffer/length
echo 1 > buffer/enable
# Set event mode in range [0 ; 15]
# One bit for each CAPx register : 1 = falling edge / 0 = rising edge
# e.g. mode = 13 = 0xd = 0b1101
# -> falling edge for CAP1-3-4 / rising edge for CAP2
echo 13 > events/change_falling_value
# Run ECAP
echo 1 > en
# Get the number of available data
cat buffer/data_available
# Read data
hexdump -v /dev/iio\:device2
# Stop ECAP
echo 0 > en
Julien Panis (2):
iio: time: capture-tiecap: capture driver support for ECAP
dt-binding: iio: time: add capture-tiecap.yaml
.../bindings/iio/time/capture-tiecap.yaml | 53 ++
drivers/iio/Kconfig | 1 +
drivers/iio/Makefile | 1 +
drivers/iio/time/Kconfig | 22 +
drivers/iio/time/Makefile | 6 +
drivers/iio/time/capture-tiecap.c | 532 ++++++++++++++++++
6 files changed, 615 insertions(+)
create mode 100644 Documentation/devicetree/bindings/iio/time/capture-tiecap.yaml
create mode 100644 drivers/iio/time/Kconfig
create mode 100644 drivers/iio/time/Makefile
create mode 100644 drivers/iio/time/capture-tiecap.c
--
2.25.1
