CC3100: SPI communication to Host crashes during sending larger files with empty IRQ

Hi Juergen,

Can you please provide some more information?

• Which SDK example are you using?
• What is the host MCU for your setup?
• Does this only happen when sending large files >1MB?
• What do you mean by 0 length IRQ?

Regards,

Charles O

Hello Charles,

we are using a Tiva Controller - the TM4C1294KCPDT with FreeRTOS. We are reading data from a SD-Card and send them over the CC3100 using the DMA feature of the Tiva. 

It does only happen on larger file sizes - as larger as faster the issue occures - the exact number I can't say at the moment.

IRQ with Zero length means that the IRQ line is indicating an interrupt, but no byte with containing the reason has been provided.

Smaller data sizes are working very nice and fast.

So our problem is the missing flow control for sending data - do you have a description how it should work?

Any recommendation what we could try to fond the root cause?

Hope this helps and best regards,

Juergen Maisel

Hello Charles,

we did that already in different versions - the issue is it is not just a little constant (currently 2ms), but it stil does not cover the problem 100%. Making the delay larger brings the data rate further down which is not acceptable.

This is why we are looking for a better solution with your help.

The effective data rate you can achieve depends on the wireless link quality which can change due to nosier environment - hence the CC3100 needs more time to send out the data.

Flow control is here the magic solution. Hve you been able to recreate the issue tranmitting larger data files?

Best Regards,

Juergen Maisel

JM3 Engineering

Grafing b. Munich

Hi,

What is the data rate you are trying to implement?

I believe the reason is cause of the problem is that the DMA data is being transferred to the buffer faster than the NWP can process. I recommend setting a little delay or pausing the DMA transfer for a bit after the dummy event is received, this should allow the NWP sometimes to empty the buffer .

Regards,
Charles O

Hello Charles,

thanks for taking care of the issue. We did some more tests with little delays according to your ideas, but not very successful. We tried delays starting with 1ms up 100ms and even that did not

resolve the issue. In addition for the appilaction it is not accepable to slow down that much. Target speed on SPI is 16 Mbit.

But let's talk about items which lead us to the root cause of the issue:

1.) CC3100 -  internal buffer size - how much is avaiable?

2.) Proper implementation of flow control  - e.g. ACK at the end of the send command (which is the only command without an acknowledge)

3.) Why does the CC3100 crash?

4.) Workaround for not having the CC3100 crashing at input buffer overflow?

5.) Is there an implicit indication on the protocoll to detect buffer full?

Thanks in advance,

Juergen