Symptom

After resolving the HID permissions issue (E-001), the CRPS module now fails during Crps.Reset() with:

Specified argument was out of the range of valid values.
(Parameter 'Tried to set a register with length 2 bytes to a length of 1')

  at DeviceLibrary.PmBus.PmRegisterEntry.set_RawValue(Byte[] value)
  at DeviceLibrary.PmBus.RegisterCollection.ReadDefinitions(PsmDeviceType type)
  at DeviceLibrary.PmBus.RegisterCollection..ctor(PsmDeviceType type)
  at DeviceLibrary.PmBus.RegisterCollection.Get(PsmDeviceType type)
  at DeviceLibrary.PmBus.Chip..ctor(IFileLogging logger, Project parent, ParsedChip chip)
  at DeviceLibrary.PmBus.Project..ctor(IModule owner, IFileLogging logger, IBusHandler handler, ProjectConfig cfg, String name, String sourceBusName, Int32 supportedClockSpeed, Boolean usePEC)
  at AccordionUno.Modules.PmbusHandler.LoadProject(String base64ByteString)
  at AccordionUno.Modules.PmbusHandler.SetValue(String name, String value)
  at CrpsHandler.Crps.Reset()
  at AccordionUno.Services.ExtensionModuleService.LoadModule(IModuleSettings m)

Root cause (suspected)

RegisterCollection.ReadDefinitions loads the PMBus register map for the CRPS PSU device type (PsmDeviceType). During loading it calls PmRegisterEntry.set_RawValue to set a default/initial value for a register — but the byte array supplied is 1 byte long while the register is declared as 2 bytes wide. This is a length mismatch between the register definition and the value initializer.

Likely causes:

1. The CRPS device register definition file has a register declared with the wrong length (2 instead of 1, or vice versa).
2. The default value initializer constructs a 1-byte array for a register that requires 2 bytes.
3. A recent change to the device library or CRPS device definition introduced a regression.

What to check

• The PsmDeviceType definition for the CRPS PSU — find the register(s) declared as 2 bytes and verify their default value initializers.
• Git log on DeviceLibrary.PmBus / CrpsHandler for recent changes to register definitions.
• Whether this error reproduces on A1 hardware / previous firmware version.

Context

Raised from project ETT00000005 R0 (B12 CB Test Station Upgrade Path). This is the second blocker on CRPS integration after E-001 (HID permissions — now resolved). Deadline 2026-06-25.

Symptom

When loading the CRPS extension module via AccordionUno.Services.ExtensionModuleService.LoadModule, the firmware throws:

Not permitted to open HID class device at /dev/hidraw0
  at HidSharp.Platform.Linux.LinuxHidDevice.OpenDeviceDirectly(...)
  at MCP2221IO.Device.Open()
  at CrpsHandler.Crps.Reset()
  at AccordionUno.Services.ExtensionModuleService.LoadModule(IModuleSettings m)

Root cause

The CRPS PSU connects via a Microchip MCP2221A USB HID bridge. On Linux, /dev/hidraw* nodes are owned by root:root with mode 0600 by default. The accordion firmware service runs as a non-root user and is denied access.

The device is physically present and enumerated — the OS finds it at /dev/hidraw0 — but the service user lacks read/write permission.

Fix

Add a udev rule targeting the MCP2221A by USB Vendor/Product ID. This is a one-time OS-level configuration — it does not grant the service sudo or root rights at runtime.

File to create on the A2: /etc/udev/rules.d/99-mcp2221.rules

SUBSYSTEM=="hidraw", ATTRS{idVendor}=="04d8", ATTRS{idProduct}=="00dd", MODE="0666"

After creating the file, reload udev and re-enumerate:

udevadm control --reload-rules
udevadm trigger

Then unplug and replug the CRPS USB cable (or reboot).

Verify the PID first:

lsusb | grep -i microchip

If the product ID differs from 00dd, substitute the correct value in the rule.

Alternatives (if broader device access is undesirable)

• Group-based: create a dedicated group, add the accordion service user to it, and scope the udev rule to that group with GROUP="accordion", MODE="0660" — tighter than 0666.
• systemd DeviceAllow: add DeviceAllow=/dev/hidraw0 rw and DevicePolicy=closed to the accordion service unit file.

Resolution

udev rule applied by Mikael Svensson 2026-06-09. Fix confirmed — HID open error no longer occurs; CRPS module now advances past USB device open. New error encountered further in initialization — see E-002.

Context

Raised from project ETT00000005 R0 (B12 CB Test Station Upgrade Path).