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.
This driver leverages counter subsystem to :
- select edge polarity for all 4 capture events (event mode)
- log timestamps for each capture event
Event polarity, and CAP0/1/2/3 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...
Modifications since v6:
- Leverage counter array components (RFC PATCH v5)
- Remove the redundant doc of 'capture' items in sysfs-bus-counter ABI file
- Add driver info to MAINTAINERS file
Userspace commands :
### CLOCK SIGNAL ###
cd /sys/bus/counter/devices/counter0/signal0
# Get frequency
cat frequency
### INPUT SIGNAL ###
cd /sys/bus/counter/devices/counter0/signal1
# Get polarity for each capture event
cat polarity0
cat polarity1
cat polarity2
cat polarity3
# Set polarity for each capture event
echo positive > polarity0
echo negative > polarity1
echo positive > polarity2
echo negative > polarity3
### COUNT ###
cd /sys/bus/counter/devices/counter0/count0
# Get ceiling (counter max value)
cat ceiling
# Reset number of overflows & current timebase counter value
echo 0 > num_overflows
echo 0 > count
# Run ECAP
echo 1 > enable
# Get number of overflows & current timebase counter value
cat num_overflows
cat count
# Get captured timestamps
cat capture0
cat capture1
cat capture2
cat capture3
# Note that counter watches can also be used to get
# data from userspace application
# -> see tools/counter/counter_example.c
# Pause ECAP
echo 0 > enable
Julien Panis (4):
dt-bindings: counter: add ti,am62-ecap-capture.yaml
Documentation: ABI: sysfs-bus-counter: add frequency & num_overflows
items
counter: ti-ecap-capture: capture driver support for ECAP
MAINTAINERS: add TI ECAP driver info
Documentation/ABI/testing/sysfs-bus-counter | 14 +
.../counter/ti,am62-ecap-capture.yaml | 61 ++
MAINTAINERS | 6 +
drivers/counter/Kconfig | 15 +
drivers/counter/Makefile | 1 +
drivers/counter/ti-ecap-capture.c | 614 ++++++++++++++++++
6 files changed, 711 insertions(+)
create mode 100644 Documentation/devicetree/bindings/counter/ti,am62-ecap-capture.yaml
create mode 100644 drivers/counter/ti-ecap-capture.c
--
2.37.3
