Can't transmit to BlueSMiRF while receiving

I have the same problem as the one described here:

http://www.sparkfun.com/cgi-bin/phpbb/v … php?t=1709

I’m running on Mac OS X 10.4.5, my BlueSMiRF is connected to an Atmel AVR ATmega128. It’s configured for 76800 bps. I can send and receive bytes half-duplex, but once my AVR starts sending a steady stream of data, i can no longer send data to the BlueS from the Mac.

It’s sending 7 bytes every 5 ms. It sends a burst for 800 µs, then does other stuff for more than 1500 µs, then begins again. If I stop the AVR execution (via gdb and the JTAGICE), so that transmission stops, suddenly the bytes are sent from the BlueSMiRF to the AVR.

Also note, RTS/CTS are never deasserted.

What’s going on here? Is the BSMiRF preventing full-duplex use? Or is it something in Mac OS X’s BT-serial port that’s doing it? I’m connecting to /dev/tty.MyBlueSMiRFName

TIA,