[Discuss-gnuradio] GMSK2 with BasicRX and BasicTX

[Brian Johnson]

Hi,

 

What sort of problems can I expect if I use the GMSK2 examples with the Basic RX/TX boards?

 

The information I have found in this discussion group suggests that the GMSK2 examples were developed only for the Flex 400 daughter boards.  Since we currently only have the Basic RX and Basic TX boards I tried it with them anyway. 

 

I modified the example to use the new carrier sense MAC code, but still had a lot of packets lost on the ping.  After digging into it a little I found that the packets were being lost on the receive side, and with a little experimentation found it could be corrected by putting a “time_sleep(0.1)” before “self.fg.send_pkt” in the MAC code  (need some time to complete the os.read before sending the packet?)

 

With this I am now getting < 5% packet loss on the ping between 2 USRPs and can successfully transfer files between the USRPs using ftp.

 

I realize that these examples were written to utilize the auto transmit/receive feature that is only in the Flex 400, but other than that are there any problems with using these boards for GMSK that I just haven’t run into yet?  I do get significantly more packet loss if I ping each USRP from the other one at the same time – would that be corrected with the auto transmit/receive feature?

 

Brian