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
