Checking signals with SSH

On the RevPi, you can check the configured signals and their values without the logiccloud portal. Use this to test the wiring, to check a PiCtory change, or to compare a value in logiccloud with the value on the device.

All commands on this page run on the RevPi. Connect with SSH first:

ssh pi@<device-ip>

The password of the pi user is printed on the sticker on the side of the housing.

The command line tool is piTest. It is part of the RevPi image.

Listing the modules

piTest -d

The command shows every module that the driver knows, with its position (Address) and its area in the process image:

Address: 0 module type: 136 (0x88) RevPi Connect 4 V1.0
Module is present
     input offset: 113 length: 6
    output offset: 119 length: 7

Every module must show Module is present.

Listing the configured signals

piTest cannot list all signal names. Read them from the PiCtory configuration instead:

python3 - <<'EOF'
import json

with open("/etc/revpi/config.rsc") as f:
    config = json.load(f)

for device in config["Devices"]:
    for section in ("inp", "out", "mem"):
        for var in sorted(device[section].values(), key=lambda v: int(v[3])):
            print(f"{device['position']:>3}  {device['name']:<18} {section:<4} {var[0]:<22} {var[2]:>3} bit")
EOF

Example output:

  0  RevPi Connect 4    inp  RevPiStatus              8 bit
  0  RevPi Connect 4    inp  RS485ErrorCnt           16 bit
  0  RevPi Connect 4    inp  Core_Temperature         8 bit
  0  RevPi Connect 4    inp  Core_Frequency           8 bit
  0  RevPi Connect 4    out  RevPiLED                16 bit
 33  RevPi AIO          inp  InputValue_1            16 bit

The columns are: position, module, section (inp input, out output, mem module configuration), signal name and bit length. The bit length decides the data type in logiccloud. See Data type mapping.

Note

This file shows the saved configuration. The driver uses the configuration that it loaded at the last driver reset. If you saved a change in PiCtory and did not reset the driver, the two can differ.

Checking one signal

piTest -v Core_Temperature

variable name: Core_Temperature
       offset: 117
       length: 8
          bit: 0

piTest -v asks the driver, not the file. If the driver does not know the name, the command prints Failed to get variable info. The logiccloud connector finds signals in the same way, so a name that fails here also fails in logiccloud.

Reading a value

Read a value once:

piTest -1 -r Core_Temperature

1 Byte-Value of Core_Temperature: 50 dez (=32 hex)

Print only the value:

piTest -1 -q -r Core_Temperature

Read a value every second until you press Ctrl+C:

piTest -r Core_Temperature

Add ,h for hexadecimal or ,b for binary output, for example piTest -1 -r RevPiLED,b.

Writing a value

piTest -w RevPiLED,1

The value is written to the process image and the driver sends it to the module. Outputs can also be read back with piTest -r.

Danger

piTest -w writes directly to the output. It does not check the state of the machine. Only write to outputs when the connected equipment is in a safe state.

Caution

piControl has no write protection between programs. If a logiccloud runtime writes the same output, the last write in the cycle wins. Your value can be overwritten after a few milliseconds. To test a logiccloud output, let the runtime write it and only read it with piTest -r.

Testing a digital output at the terminal

To prove that the PiCtory positions match the DIN rail, switch one output and measure it at the terminal:

1. Make sure that no load is connected to the output, or that switching it is safe.
2. Write 1: piTest -w O_1,1.
3. Measure the voltage at the terminal of output 1 on the module that you expect.
4. Write 0: piTest -w O_1,0.

If the voltage appears on a different module, the positions in PiCtory are wrong.

Example: status LED of the base module

The RevPiLED output of the base module controls the LEDs on the front of the housing. Each LED uses a group of bits. The bit layout depends on the base module.

RevPi Connect 4

The RevPi Connect 4 has RGB LEDs. Each LED uses 3 bits: the lowest bit is red, the middle bit is green and the highest bit is blue.

LED	Bits	Red	Green	Orange (red + green)	Blue
A1	0–2	1	2	3	4
A2	3–5	8	16	24	32
A3	6–8	64	128	192	256
A4	9–11	512	1024	1536	2048

Other colours combine the bits of one LED, for example red + blue (5 for A1) or green + blue (6 for A1). LED A5 uses the bits 12–15. See the KUNBUS documentation of the RevPi Connect 4 for this LED.

To switch several LEDs, add their values. For example, 10 switches A1 green (2) and A2 red (8).

piTest -w RevPiLED,1    # A1 red
piTest -w RevPiLED,2    # A1 green
piTest -w RevPiLED,4    # A1 blue
piTest -1 -r RevPiLED   # read back the value
piTest -w RevPiLED,0    # all LEDs off

Caution

Older RevPi Connect models (RevPi Connect, Connect+, Connect S) use another layout with 2 bits per LED. On these models, the same value switches another colour or another LED. Check the KUNBUS documentation of your base module before you use a table from another model.

RevPiLED is 16 bits wide and holds all LEDs. Writing a new value changes all LEDs at the same time. To change one LED only, read the current value, change the bits of that LED, and write the complete value back.

RevPiLED needs no wiring and no I/O module, and you can see the result on the housing. This makes it useful for a first test of a logiccloud connection. See Example: reading and writing signals.

Resetting the driver

After a change in PiCtory, load the configuration into the driver:

sudo piTest -x

This has the same effect as Tools > Reset Driver in PiCtory. Then restart the logiccloud runtime. On the RevPi Bookworm image, sudo asks for the password of the pi user.

Command overview

Command	Purpose
piTest -d	List the modules
piTest -v <name>	Show offset, length and bit of a signal
piTest -1 -r <name>	Read a value once
piTest -r <name>	Read a value every second
piTest -w <name>,<value>	Write a value
sudo piTest -x	Reset the driver and load the saved configuration
lsmod | grep piControl	Check that the driver is loaded
ls -l /etc/revpi/config.rsc	Check that the PiCtory configuration exists