Re: [uCsimm] Problems with RTS and CTS in uCsimm

From: Vladimir Gurevich (
Date: Fri Jan 05 2001 - 11:48:05 EST

Hello Asier,

Asier Goikoetxea Yanci wrote:

> Well, if I connect uCsimm's ttyS0 port to a PC, and execute agetty command
> from telnet in uCsimm (agetty -w -I 'AT\015' 9600 ttyS0), I can see in the
> minicom, in the PC, AT string and after that starts the login. It seems that
> works. But if I connect uCsimm's ttyS0 port to a modem and type de same
> command from telnet, it do the same as connectting to the PC, I mean, the
> modem will recive AT command, but it doesn´t inicialize, so I cannot connect
> to uCsimm via modem. I have disabled DCD, DSR, DTR, RTS and CTS. I only use
> to RxD, Txd and GND to comunicate the uCsimm whith the modem. Wath am I
> doing wrong?

Well, here are a couple of suggestions:

1) I hope you use a correct cable to connect uCsimm to the modem.
   Remember, that your PC is a DTE and your modem is a DCE. Thus, Tx and
   Rx pins on the cable that you use to connect uCsimm to the modem
   should be swapped (compared to the cable you use to connect uCsimm to
   your PC).

2) "AT<CR>"
 command itself does not initialize a modem. It is more like
   a NOP command. If you want your modem to answer the call automatically,
   I suggest you use the following sequence:

   "AT &F E0 Q1 S0=1\015"

   Q1 disables the result codes (otherwise, agetty will interpret modem's
   "OK" as a login name)

Let me know whether it helps.

Happy hacking,

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