ANT Forum

Hi,

I am getting a EVENT_QUE_OVERFLOW(0x35)message periodically. Seems to be occurring every 8 to 10 seconds. When the error occurs my data becomes corrupt, but then recovers for a short time before another EVENT_QUE_OVERFLOW is thrown. When the error occurs the SEN line goes generally high(busy)and the SOUT line goes low. I am using the ANT+ BSBC simulator source code modified to fit my application. I am not sure how to deal with this error and/or why it might be happening.

Any insight would be greatly appreciated.

Thanks,

Cody      

The timing diagram is not attached so if you could attach it that would help.

Thanks!      

Hi,

According to your timing diagram (attached below), the host is asserting MRDY which indicates that the host wishes to enter into transmit mode. Then ANT asserts SEN which indicates the start of a message transfer. After that, the host asserts SRDY which indicates that the host is ready for communication. The host then should wait for ANT to transmit the SYNC byte which indicates the direction for the remaining message bytes.

In the timing diagram below, the SYNC byte is 0XA4 which means that ANT will transmit the rest of the message bytes. However, the timing diagram shows that the host is sending at the same time byte 0x14 to ANT which should not be happening. The reason behind this is that ANT uses a half-duplex synchronous master serial interface in synchronous communication; which means communication can only happen in one direction at a time (either ANT->Host or Host->ANT).

Please refer to section 3 'Synchronous Serial Interface';specifically section 3.5 'Operating Mechanism', in the document 'Interfacing with ANT General Purpose Chipsets and Modules' for more details about synchronous serial communication (link below):
http://www.thisisant.com/images/Resources/PDF/Interfacing_with_ANT_General_Purpose_Chipsets_and_Modules.pdf      

[img size=841]http://www.thisisant.com/images/fbfiles/images/untitled.JPG[/img]      

I have made the fix that you suggested, but this did not resolve the EVENT_QUE_OVERFLOW. FYI: I also noticed that the sample code for the BSBC profile also has the same issues.

Fix: I was not servicing the incoming messages as quickly(4Hz) as ANT was trying to send them to my MCU. I now check if the buffer needs servicing every time I take a sample. This seems to be a bit overkill, but solves the problem.

Thanks for the help.      

That's great!

Thanks for the note regarding BSBC reference code. The code will be reviewed.