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11 December 2012 07:41 AM

Eugen Newbie

Total Posts: 2

Joined 2012-12-10

Hi everyone,

We are experiencing a problem while communicating with a nRF24AP2-1CH using the asynchronous interface (UART at 19200 baud). Only Acknowleged Data is used.

The problem is that we are sending an Acknowledged Data Message and immediately getting an event message "MESSAGE_SIZE_EXCEEDS_LIMIT", after this we do a retry to send the same message and we receive the next (periodic) broadcast message and the Ack, meaning that te data was successfully transfered over radio.

In attachment 3 images images showing this situation (Images "Error_zoomX" are just the zoomed messages to show they are the same). CH1 is the RX pin of AP2, CH2 is the TX pin of AP2 and CH3 is the RTS pin of AP2.

Any idea why this issue happens?

Thanks.

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11 December 2012 11:11 AM #1

Harrison Administrator

Total Posts: 745

Joined 2012-09-14

Hi,

Are you asserting the SLEEP line while RTS is high?

On nRF24AP2 parts a rare timing error can occur when the SLEEP line is asserted while the AP2 is in the middle of processing which can cause it to attempt to process a message and sleep simultaneously causing the MESSAGE_SIZE_EXCEEDS_LIMIT event to go off.

The solution is to just assert the SLEEP line while RTS is not being asserted. It's fine to de-assert the SLEEP line while RTS is high or low but only assert SLEEP after RTS H->L transition, or while RTS is low.

Cheers

12 December 2012 02:29 AM #2

Eugen Newbie

Total Posts: 2

Joined 2012-12-10

Hello Harrison,

You nailed it!

We were asserting SLEEP immediately after RTS goes H and I guess interrupting the AP2's processing of the message.

Thanks for the help!

12 December 2012 07:04 PM #3

Harrison Administrator

Total Posts: 745

Joined 2012-09-14

Glad to have helped!

Happy Developing!

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nRF24AP2 random event message “MESSAGE_SIZE_EXCEEDS_LIMIT” [SOLVED]

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