CC2541: CC2541 as central: random disconnection (reason LL_STATUS_ERROR_CONN_TIMING_FAILURE - 0x3F)

j.seydoux

Part Number: CC2541

Hello,

I am facing random disconnection issues (disconnection reason 0x3F) after several seconds or minutes after connection establishement (the connection does not remain more than 2-3 minutes).

The CC2541 acts as a central-observer and communicates via I2C to a master (CC2541 is the I2C slave).

After several tests, it seems that the issue occurs only when a connection is established while I2C transfers are on-going. The following tests were done:

No I2C transfers during connection establishement and while connected (I2C slave still active) -> connection remain at least 30 minutes.
I2C transfers during connection establishement and I2C transfers while connected -> random disconnection (reason 0x3F) after a few seconds (or minutes).

The I2C slave driver used is the one provided by Texas Instruments and it is used with interrupts. The master requests 8 bytes of data each 200ms (I2C frequency set to 10kHz). The BLE stack version used is 1.4.2.

My questions are:

How can I resolve this issue on the I2C side?
How can I setup a more robust connection using GAP parameters (or other ways)?

Thank you in advance,
Johann

over 9 years ago

0 Tim C over 9 years ago

TI__Mastermind 34660 points

You're likely starving the controller somehow such that it does not get to process for each connection event, its timing then gets thrown off, and it drops the connection. You could try using a longer connection interval but really you should track down the root cause to figure out what is starving the controller by toggling GPIO's during application processing, I2C driver processing, etc.

0 j.seydoux over 9 years ago in reply to Tim C

Intellectual 740 points

After investigation, I've found that the disconnection issue comes from the I2C interrupt being executed for too long.

The reason why the I2C interrupt is so long is that, for an unknown reason, the master MCU detects an unexpected START/STOP condition on the bus generated by the CC2541. The I2C signals show that this occurs when the CC2541 is stretching the clock (the I2C signals - Saleae logic - are joined to this post).

Do you have any information on the I2C slave driver of the CC2541 that could help? Any working examples of this I2C driver?

This issue is very annoying and I spent a lot of time on this issue.

Thank you.CC2541-I2C-bug.zip