BLE bootloader failing on specific Android tablet

RE: BLE bootloader failing on specific Android tablet

Simonr — Fri, 31 Jan 2025 14:59:22 GMT

This is a problem with the Bluetooth stack on the Android side, and unfortunately there isn't really any good ways of dealing with this from the nRF side, since the A8 tablets will try to negotiate for a higher MTU than what is supported, which will result in the SoftDevice controller disconnecting due to the Bluetooth spec. violations. The best way to work around this would be to not support longer packets, and for example decrease the max MTU size allowed on the nRF side if you run into one of these disconnects.

The correct way to fix this is in the Bluetooth stack on the tablet side, but that is something that must be done by the tablet vendor.

Best regards,

Simon

RE: BLE bootloader failing on specific Android tablet

damras — Wed, 29 Jan 2025 15:21:08 GMT

This didn't seem to work. I can see that it changes the Tx_LEN, but in DFU we are concerned with Rx_LEN which I think can only be negotiated by the Central.

RE: BLE bootloader failing on specific Android tablet

damras — Wed, 29 Jan 2025 15:17:11 GMT

Some more findings from using the le_param_updated & on_le_data_len_updated callbacks on our nrf5340 zephyr code and the nrf ble sniffer.

We have noticed in the failure scenario the len gets updated to 27 bytes but Central sends 28 bytes, which causes the Peripheral to disconnect. This is the first DFU packet.

Samsung A9 CONFIG_BT_CTLR_DATA_LENGTH_MAX=251 (SUCCESS)
00> [00:01:52.076,507] <inf> bluetooth: Data length updated. Length TX:251/RX:27 bytes, time 2120/328 us
00> [00:01:52.931,549] <inf> bluetooth: Data length updated. Length TX:251/RX:31 bytes, time 2120/2120 us
00> [00:01:53.561,187] <inf> bluetooth: Connection parameters updated: interval 15 ms, latency 0 intervals, timeout 5000 ms
00> [00:01:56.996,002] <inf> bluetooth: Connection parameters updated: interval 45 ms, latency 0 intervals, timeout 420 ms

640 26.601 Central_0x639cb678 LE 1M LE LL 31 14522µs 1 1 True 35 L2CAP Fragment Start

Samsung A8 CONFIG_BT_CTLR_DATA_LENGTH_MAX=27 (SUCCESS)
00> [00:00:55.239,135] <inf> bluetooth: Data length updated. Length TX:27/RX:27 bytes, time 2120/328 us
00> [00:00:56.503,204] <inf> bluetooth: Connection parameters updated: interval 15 ms, latency 0 intervals, timeout 5000 ms
00> [00:01:00.010,528] <inf> bluetooth: Connection parameters updated: interval 37 ms, latency 0 intervals, timeout 420 ms

6512 116.366 Peripheral_0x9b2d1355 LE 1M LE LL 27 149µs 0 1 True 33 L2CAP Fragment Start

Samsung A8 CONFIG_BT_CTLR_DATA_LENGTH_MAX=251 (FAIL)
00> [00:01:50.524,414] <inf> bluetooth: Data length updated. Length TX:251/RX:27 bytes, time 2120/328 us
00> [00:01:51.739,501] <inf> bluetooth: Connection parameters updated: interval 15 ms, latency 0 intervals, timeout 5000 ms

00> [00:01:56.793,609] <err> bluetooth: Disconnected (reason 0x08)

333 8.185 Central_0x48302c55 LE 1M LE LL 28 151µs 0 0 True 36 L2CAP Fragment Start

RE: BLE bootloader failing on specific Android tablet

Sigurd Hellesvik — Thu, 23 Jan 2025 11:39:33 GMT

See https://academy.nordicsemi.com/topic/blefund-lesson-3-exercise-2/ on how to update_data_length(). Does this work?

RE: BLE bootloader failing on specific Android tablet

damras — Wed, 22 Jan 2025 11:55:33 GMT

CONFIG_BT_CTLR_DATA_LENGTH_MAX=27 in hci_rpmsg/zephyr/.config

RE: BLE bootloader failing on specific Android tablet

damras — Wed, 22 Jan 2025 11:50:44 GMT

I am also working with Mathew on this issue.

changing CONFIG_BT_CTLR_DATA_LENGTH_MAX=27 (Default) fixed the issue on the A8.

If there a way for the Nrf Connect Device Manager to request this from the nrf5340 or changing CONFIG_BT_CTLR_DATA_LENGTH_MAX at runtime in the nrf5340 so that for tablets that are non-A8 we can set a higher rate.

RE: BLE bootloader failing on specific Android tablet

Sigurd Hellesvik — Wed, 22 Jan 2025 11:47:11 GMT

[quote user="matkey"]In our proj.conf we comment out CONFIG_BT_CTLR_DATA_LENGTH_MAX=251 and then the bootloader is working again. Is that what you had in mind?[/quote]

Sounds reasonable to me. Can you check what CONFIG_BT_CTLR_DATA_LENGTH_MAX defaults to in build/hci_rpmsg/zephyr/.config when you no longer set it explicitly?

RE: BLE bootloader failing on specific Android tablet

Mathew Key — Tue, 21 Jan 2025 17:11:00 GMT

Not the proj.conf - the child_image/hci_rpmsg.conf

RE: BLE bootloader failing on specific Android tablet

Mathew Key — Tue, 21 Jan 2025 16:20:39 GMT

Hi Sigurd,

If I understand it right, the A8 can only handle 27 byte packets as the radio is screwed up (still 3 years later from that ticket).

In our proj.conf we comment out CONFIG_BT_CTLR_DATA_LENGTH_MAX=251 and then the bootloader is working again. Is that what you had in mind?

Mat

RE: BLE bootloader failing on specific Android tablet

Sigurd Hellesvik — Tue, 21 Jan 2025 14:41:32 GMT

Hi,

We have seen issues with the A8 before. See https://devzone.nordicsemi.com/f/nordic-q-a/88202/dfu-error-unable-to-write-op-code-3-error-133/372825#372825. Does this comment tell you what you need?

Regards,
Sigurd Hellesvik