Read the digital input state of GPIO pins, with optional blocking wait for a target level.
Syntax
lager gpi [NETNAME] [OPTIONS]
Arguments
| Argument | Description |
|---|
NETNAME | GPIO net name (optional if default is set). If omitted, lists all available GPIO nets. |
Options
| Option | Description |
|---|
--box BOX | Lagerbox name or IP address |
--wait-for LEVEL | Block until pin reaches this level (high, low, 1, or 0) |
--timeout SECONDS | Timeout in seconds for --wait-for (default: wait forever) |
--scan-rate HZ | LabJack streaming sample rate in Hz (advanced) |
--scans-per-read N | LabJack scans per read batch (advanced) |
--poll-interval SECONDS | Poll interval in seconds for non-streaming drivers (advanced) |
Usage
Basic Read
# Read input state
lager gpi BUTTON1 --box my-lager-box
# Using default net
lager gpi
# List available GPIO nets (omit net name)
lager gpi --box my-lager-box
Wait for Level
Block until a pin reaches a target level. Useful for waiting on hardware events like button presses, interrupt lines, or device ready signals.
# Wait for pin to go high
lager gpi BUTTON1 --wait-for high --box my-lager-box
# Wait for pin to go low with 10-second timeout
lager gpi INT_PIN --wait-for low --timeout 10
# Wait for rising edge (pin goes to 1)
lager gpi READY --wait-for 1 --timeout 30
Advanced Streaming Options
For LabJack T7 hardware, the --wait-for command uses high-speed streaming to detect level changes. You can tune the streaming parameters:
# Custom scan rate (default varies by driver)
lager gpi TRIGGER --wait-for high --scan-rate 10000 --timeout 5
# Custom scans per read batch
lager gpi TRIGGER --wait-for high --scan-rate 5000 --scans-per-read 500
# For non-streaming drivers, adjust poll interval
lager gpi BUTTON --wait-for low --poll-interval 0.05 --timeout 10
Output
Basic Read
Returns the digital state:
0 - Low (0V)1 - High (3.3V or 5V depending on hardware)
Wait for Level
Returns the elapsed time in seconds when the target level is reached:
$ lager gpi INT_PIN --wait-for low --timeout 10
Pin reached LOW after 2.34s
Supported Hardware
| Device | Pins | Voltage | Wait-for Method |
|---|
| LabJack T7 | FIO0-FIO7 | 3.3V logic | Streaming (high-speed) |
| MCC USB-202 | DIO0-DIO7 (0-7) | 3.3V/5V TTL | Polling |
| Aardvark | 0-5 (SCL, SDA, MISO, SCK, MOSI, SS) | 3.3V | Polling |
| FT232H | 0-15 (AD0-AD7, AC0-AC7) | 3.3V | Polling |
Aardvark and FT232H GPIO support is currently disabled and may be re-enabled in a future release. LabJack T7 and MCC USB-202 are the active GPIO backends.
Aardvark Pin Mapping
The Aardvark I2C/SPI adapter exposes 6 GPIO pins on its 10-pin header. Pins can be specified by number or signal name:
| Pin | Name | Header Pin |
|---|
| 0 | SCL | 1 |
| 1 | SDA | 3 |
| 2 | MISO | 5 |
| 3 | SCK | 7 |
| 4 | MOSI | 8 |
| 5 | SS | 9 |
FT232H Pin Mapping
The FT232H provides 16 GPIO pins across two ports:
| Pins | Names | Description |
|---|
| 0-7 | AD0-AD7 | Port A data pins |
| 8-15 | AC0-AC7 | Port A control pins |
Examples
# Check if button is pressed
STATE=$(lager gpi BUTTON1 --box lab-gw)
if [ "$STATE" -eq "1" ]; then
echo "Button pressed"
fi
# Read multiple inputs
lager gpi BUTTON1 --box lab-gw
lager gpi SENSOR_INT --box lab-gw
lager gpi FAULT_PIN --box lab-gw
# Wait for device ready signal
lager gpi READY_PIN --wait-for high --timeout 30 --box lab-gw
# Wait for interrupt (active-low)
lager gpi INT_N --wait-for low --timeout 5 --box lab-gw
# Scripted: wait for button press, then proceed
echo "Press the button..."
lager gpi BUTTON --wait-for high --timeout 60 --box lab-gw && echo "Button pressed!"
Notes
- GPI is for reading input pins only
- Use
lager gpo to set output pins
- Default net can be set with
lager defaults add --gpio-net
- Pin must be configured as input in net configuration
- USB-202 channels can be specified as
0-7 or DIO0-DIO7
--wait-for blocks the process until the target level is detected or the timeout expires--scan-rate and --scans-per-read only apply to LabJack T7 streaming; they are ignored by other drivers--poll-interval applies to non-streaming drivers (USB-202, Aardvark, FT232H); ignored by LabJack
