🚀 go-pugleaf

Help! I need an rs-232 guru;

     I have a serial interfacing problem. I bought a receiver which has
a serial interface in the back for computer control. I want to be able
to control it from my HP-48 calculator, which has a serial interface.
The receiver has the following specs:

9600 baud, even parity, 7 data bits 1 start, 1 stop, half duplex, and
RTS/CTS hardware handshaking. Considered DCE. None of this setup is
changeable. The pinout is as follows:

1- Scan feedback; +5 volts = receiver unsquelched
2- Rx data
3- Tx data
4- DTE ready
5- Signal ground
6- DCE ready
7- RTS
8- CTS
9- Shield ground


The calculator can do 9600 baud, even parity, full duplex. The problem is,
it only has Tx  Rx  and ground.  It can do xon/xoff handshaking, but not
hardware handshaking. The calculator is DTE, and cannot be changed to
half duplex.

On the receiver, I have tried shorting DTE/DCE, and the receiver thinks
it's connected. Then, I tried shorting RTS/CTS and running the Tx/Rx 
from the calc straight through. This does not work. On the calculator,
when I try to send a command which requires a response, I get parity errors,
and a few characters of garbage. If I tell the calc to ignore parity errors,
I do not even get the expected number of characters back from the receiver.
I think the problem lies in the fact that the calculator does not do RTS/CTS,
and I cannot fake it out by shorting them, but I don't know enough about
hardware handshaking to be sure. It seems I need some sort of protocol
converter, which would talk to the calculator "normally" with no handshaking,
and pass the stuff back and forth to the receiver with RTS/CTS. Is this true,
and what would it cost?

I can connect the receiver to my pc, run procomm terminal software, and
type commands manually. But this ONLY will work if I tell procomm to use
RTS/CTS handshaking. If I short RTS/CTS on the receiver when connected to the
pc, this will not work. All of this leads me to believe that I cannot
get the calculator to talk to the receiver without RTS/CTS for real.

Is the kind of converter I'm talking about practical/necessary, or am I
just not doing something right? Please respond to me directly. Thank you
very much.


peraino@gmuvax.gmu.edu


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