CC1120: CC1120 - Going from Variable Packet Length to Fixed Length

Sutton Mehaffey

Part Number: CC1120

I am controlling 2 TrxEB Eval boards from 2 ARM microcontrollers. It works well with Variable Packet Length. My length is 10. The length that is received is 13. (My packet plus Address byte plus 2 status bytes RSSI and CRC - packet length byte not included in packet size.

When going to a fixed length of 10, nothing works. I changed PKTLEN to 0x0A (was 0xFF) and PKT_CFG0 to 0x00 (was 0x20). I'm not including the packet length byte any more in the Create_Packet function. Just the Address Byte, and my 10 bytes. What else am I missing?

Thanks.

Sutton

over 5 years ago

0 Sutton Mehaffey over 5 years ago

Expert 1205 points

Looks like the first packet is received fine. 2nd packet is transmitted by the TX, but the NUM_RXBYTES register in the RX never flags the 2nd packet. Works fine if packet is variable length. Same code different register values. 50 packets transmitted in variable packet mode all get received by the RX.

0 Sutton Mehaffey over 5 years ago in reply to Sutton Mehaffey

Expert 1205 points

I figured it out. I was still sending 1 extra byte when writing to the FIFO. For fixed length you send one less (packet length goes away). Works fine now.

0 Eirik V over 5 years ago in reply to Sutton Mehaffey

TI__Guru 56590 points

Happy to hear you figured it out.

Sub-1 GHz

Sub-1 GHz forum

CC1120: CC1120 - Going from Variable Packet Length to Fixed Length