I’m running into what I think is a mismatch between actual port settings on the FEZ Domino and what’s realized on the RS232 Shield that’s attached to it.
In plugging the RS232/Domino equipment to my PC, I get consistent and reliable communications. When I remove the DB9 from the PC and attach it to my TNC, I can’t receive any data, but I do see data transmitted. When the TNC is connected to the PC, I can receive and transmit reliably and consistently.
Further, with a small oscilloscope attached, I see absolutely no signal coming from the TNC when its attached to the RS232 Shield from GHI Electronics. I do see signal when it’s attached to the PC.
TNC has only 3 wires, GND, RX and TX. Signal is standard RS232 ±12V DC swing on communication signal.
TNC communicates great with PC - no issues. O-Scope shows standard ±12VDC RS232 signals both ways.
PC to Shield/Domino working both ways, no issues. DB9 connector straight-thru with all 9 pins.
TNC Receives data FROM Domino/Shield and transmits it over the air. However, Shield/Domino not seeing any data from TNC when received by TNC. O-Scope shows no data incoming.
This is rather puzzling - I tried calling GHI to see if the RS232 shield is hardware strapped for Hardware RTS/CTS or DTR/DSR flow control, but they directed me here ???:-\
Anyone got a clue by four?