Hi
I am using the TS-ISO485 RS485 driver card with my TS-7250. Is
anybody using this card in half-duplex mode? I am having problems receiving
data in this mode (TX is fine). The problem is that the RS-485 driver chip used
for TX/RX in half-duplex mode always has it’s DE/!RE high (measured it
with a scope) – in other words it is configured as a driver. These pins
on the driver are controlled by the TX_ENA output signal of a CPLD connected to
the UART (16C550). There is a number of modem control lines (RTS, CTS, DTR,
DSR, OUT1, OUT2, etc.) connected between the UART and CPLD. I need to
know what the state of these modem control lines should be in order to drive
the TX_ENA output on the CPLD low. I have tried a number of combinations, but
with no luck.
My test application is very simple: open the device, configure
the driver and then do a read().
If I reboot the TS-7250 (and before I start my app), the
TX_ENA signal is low and I can see data being received on the RX pin of the RS-485
driver. As soon as I start my application the TX_ENA signal goes high and no
data is received on the RX pin.
Any suggestions will be appreciated.
Thanks
Wouter