IWR6843AOP: LVDS/CBUFF Maximum Frame Size

Pablo Fdez

Part Number: IWR6843AOP

Hello,

I'm using CBUFF to stream data over the LVDS lines and apparently I have hit a maximum in the frame size (the sum of all CBUFF entries). If I try to send more than 128kB (0xFFFF CBUFF units?), the EDMA queue overflows full of the same event (from the CBUFF linked list) repeated 16 times. The CBUFF FIFO input seems to get stuck.

I using software trigger and CRC. I'm aware of the limit in the CBUFF entries size (0x3FFF units), but it doesn't seem to depend on the number or size of CBUFF entries, only on the total size.

I have not found anything in the documentation so, could you please confirm the limitation or help me found the issue?

Thank you,

Pablo

9 months ago

0 Abhishek Karkisaval 9 months ago

TI__Expert 8790 points

Hi Pablo,

CBUFF fifo has a size of 16KB. So, you need to make sure that the next write to the fifo happens only after the first one has been transmitted out. As EDMA transfer will be faster than the CBUFF transmitting data out of LVDS, this careabout is important

Regards

0 Pablo Fdez 9 months ago in reply to Abhishek Karkisaval

Prodigy 20 points

Hi Abhishek,

Thanks for your advise. I have checked that the CBUFF transfer thresholds are correctly set (following the programmer's guide) to throttle the EDMA transfers:

Regards,

Pablo

0 Abhishek Karkisaval 9 months ago in reply to Pablo Fdez

TI__Expert 8790 points

Hi Pablo,

To transfer more than 128KB, you can space out the transfers sent out of LVDS. If the data written into CBUFF is not sent out of LVDS, in that case CBUFF cannot accept further data through EDMA. You can transfer the next 128KB only after the current one is complete

Regards

Sensors

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IWR6843AOP: LVDS/CBUFF Maximum Frame Size