unlock failed with error code 0x01 and 0x04

[the-yellow-sky]

Hi Benjamin,

I hope you’re doing well. I’ve been struggling with an issue while trying to connect my ESP32-S3 to an Omron device HEM-7155T using BLE with the NimBLE library. Despite many attempts, I keep hitting a wall with the unlock process and could really use your help.

Problem Description:
I can connect to the Omron device, discover its services and characteristics, and set up a secure connection.
I’ve registered for notifications on the unlock characteristic.
When I send the unlock command (prefix 0x01 followed by a 16-byte unlock key), I get a notification back saying the unlock failed with error code 0x01. (before setting up secure connection, I got error code 0x04)

What I’ve Tried:
Double-checked that my unlock key matches the one from a working Python example.
Experimented with sending the command without the 0x01 prefix, but no luck.
Made sure the connection is secure before sending the command.
Checked the device state and even tried resetting bonding info, but the error still happens.

My Questions:
Could you explain what error code 0x01 and 0x04 mean in this case?
Are there specific steps or requirements for unlocking the Omron device with NimBLE that I might be missing?
Is there any documentation on the error codes the device returns during the unlock process?
I’ve failed so many times that I’m at my wit’s end, so I’d really appreciate any advice or insights you could share. If you need more details or logs to figure this out, just let me know—I’m happy to provide them.

Thank you so much for your time and help!

[userx14]

Hi @the-yellow-sky ,

do you use the esp-32-bridge branch of this repository or some other self written code for that?
I don't have access to the device model you work with, so the following is just info from other device models. When sending the command with the 0x01 prefix, the omron has to be in pairing mode (for my device, long pressing bt button, blinking P on LCD), and will store the 16 byte sequence as the new unlock key. For the sequence you can use arbitrary values, so there is nothing special about the one in the code. When the device is restarted in normal bluetooth mode (shortpress bt button), with the 0x00 prefix you can request to unlock the device when you connect again with other devices, even when they have different bt-mac adresses. For this you just have to send the 16 byte code you programmed in the first step.

Do you have an Android phone that you can test with?
To narrow down the problem you could try the nrfConnect app that can read and write bluetooth characteristics. I'll try to link another issue with instructions later.

Best regards,
Benjamin

[userx14]

Hi,

here was the other issue where I have some documentation on how to test the pairing with the nrfConnect app:
#16 (comment)

So I would propose:

• try with the nrfConnect Android app, first with the commands in the xml, then try the ones you use in your code
• test the esp32 bridge version, to see if it works with the esp32s3 and Arduino core that you are using. I don't remember which esp32 I tested with.

I think I have so far not used the NimBLE library, only the one that ships by default with the arduino IDE.
When testing it is very important to always power cycle (for my device start/stop button) the omron and reenter pairing mode, when some wrong code was sent. Otherwise even if one sends a correct code it might report an error.

Unfortunately I don't have additional information about the error codes.

Best regards,
Benjamin