The Industrial Raspberry Pi Forum

Posted: **29 Jan 2025, 14:55**

Hello,

I am using the Revolution Pi Compact device and I would like to use the persistent EERAM memory to store retain variables.

According to the forum, the path to this memory is supposed to be:
/sys/bus/nvmem/devices/1-00500/nvmem

However, on my device, the /sys/bus/nvmem/devices/ directory is empty, which prevents me from accessing the file.

My question is: where can I find this file, and how can I read from and write to it?

Thank you in advance for your response.

Best regards,

Posted: **21 Feb 2025, 14:14**

Hello bg rania so I've just made a test setup using the latest RevPi OS Bookworm (250124-revpi-bookworm-arm64-default.img) and a RevPi Compact. So that's what I got. I am still at a loss as to whether a change has been made here or whether the "EERAM Susbsystem" works differently due to the large number of files:

Code: Select all

pi@RevPi21844:~$ sudo tree /sys/bus/nvmem/devices/nvmem_cust0
/sys/bus/nvmem/devices/nvmem_cust0
├── nvmem
├── of_node -> ../../../../../../firmware/devicetree/base/soc/nvmem/nvmem_cust
├── power
│   ├── autosuspend_delay_ms
│   ├── control
│   ├── runtime_active_time
│   ├── runtime_status
│   └── runtime_suspended_time
├── subsystem -> ../../../../../../bus/nvmem
├── type
└── uevent

4 directories, 8 files
pi@RevPi21844:~$ sudo tree /sys/bus/nvmem/devices/nvmem_otp0
/sys/bus/nvmem/devices/nvmem_otp0
├── nvmem
├── of_node -> ../../../../../../firmware/devicetree/base/soc/nvmem/nvmem_otp
├── power
│   ├── autosuspend_delay_ms
│   ├── control
│   ├── runtime_active_time
│   ├── runtime_status
│   └── runtime_suspended_time
├── subsystem -> ../../../../../../bus/nvmem
├── type
└── uevent

4 directories, 8 files

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