Post by thread:RS 232 Help?

Hi I am trying to find the pin out and voltage levels (and what ever else is neded to interface ) for a rs232 serial port. Any ideas would help. Thanks & 73 KC7JHO ICQ# 3044899 Amature Radio, It's not just for Talking any more!

On Tue, 7 Oct 1997 06:49:43 -0500 "Nathan Jhonson......KC7JHO" <spam_OUTkc7jhoTakeThisOuTFLINTHILLS.COM> writes: >Hi I am trying to find the pin out and voltage levels (and what ever >else is >neded to interface ) for a rs232 serial port. Any ideas would help. The very basics... Use an MC1488 or similar to drive the RS232 (EIA232) line. The data idles in the mark condition, which is +5 volts going into the 1488 and typically -12V coming out of the 1488. The start bit and other 0 bits are 0 volts into the 1488 and +12V on the RS232 line (out of the 1488). The minimum pinout (almost) on a 25 pin D connector is: 1 - shield 2 - Data from the Data Terminal Equipment 3 - Data from the Data Communications Equipment 4 - Request to Send from the DTE 5 - Clear to Send from the DCE 7 - Signal ground DTE is typically a terminal. DCE is typically a modem. The easy way to remember the data direction is "terminal talks on two" (remember all the T's). RTS and CTS are TRUE at +12V and FALSE at -12V. this is all pretty much from memory of working with a Lear Siegler ADM-1 terminal (a while back!). Harold

Thanks I am trying to do some expermints in AFSK transmission and reciving data with 4 of the 567 ic (@$0.49 each it should be fun to try) is the data coming out of the serial port, #2 line, in bianary coded decimal? or am i way off track. I am studing digital electronics and trying to learn as I go. Thanks for your help. 73 KC7JHO ICQ# 3044899 Amature Radio, It's not just for Talking any more!

On Tue, 7 Oct 1997 12:01:24 -0500 "Nathan Jhonson......KC7JHO" <.....kc7jhoKILLspam@spam@FLINTHILLS.COM> writes: >Thanks I am trying to do some expermints in AFSK transmission and >reciving >data with 4 of the 567 ic (@$0.49 each it should be fun to try) is the >data >coming out of the serial port, #2 line, in bianary coded decimal? For AFSK demodulation, I really like the Exar XR2211. I've used it for years and years. They also have the XR2206 that is nice for AFSK generation. Data on RS232 lines is generally asynchronous ascii. It's one start bit (a zero or space) followed by 7 or 8 (or in Baudot 5 or maybe 6) data bits, least significant bit sent first, then followed by an optional parity bit, then followed by 1 or 2 stop bits (or in Baudot, 1.5 stop bits). I think pretty much everyone is now doing 8 data, no parity and 1 stop bit. You can convert BCD to ascii by adding 0x30. Harold