ethernet over cpri protocol congiuration problem for bits order

[luoqiaofa]

Hello QorIQ team:

     I have encounter an problem about ethernet packet over cpri protocol, we need communication RRU with ethernet, 

but the rru use non-standard cpri protocol,  that is , the RRU use MSB first bits order to send ethernet bits stream.  but standard protocol use LSB first bits order, please refer to the attatchment stardard_ethernet_cpri_20190924084130.jpg

unfortunately， the communication partner RRU can't be modifed for this bits order, so we expect the b4860 side can configure this to MSB, please refer to the attatchment partner_recv_bitorder_20190924084209.jpg, we dump the data and analysis.

can you help us to resolve the problem, it's very important us, thank you very much.

note: the RRU is not belongs to our company, but we must communicate with it

hope you to give use good news.

thank you very much

[yipingwang]

That spec 4.2.7.2.2 is talking about sample order and bit order as well, but this sample order and bit order rule is for CPRI hardware. The bit order defined in B4 RM I15I14I13...I0, Q15Q14Q13..Q0 is for software in system memory. There is a MAP module in CPRI which will map the data format from system memory to the data format in CPRI hardware. See RM Figure 10-8. Example of Mapping of 16bits IQ samples. So in the system memory the bit order is I15I14I13...I0, Q15Q14Q13..Q0, while in the CPRI hardware (basic frames) the bit order is I0Q0I1Q1...I15Q15.

For transparent mode, the RM just mentions that the whole frame will be sent or received to system memory. If 2 B4 devices connected by CPRI, they can use transparent mode to exchange data, and the RX buffer received in 1 device will look exactly the same as the data in the TX buffer in another device.