[En-Nut-Discussion] Ethernet 1.3 w/modem

[Rick Collins]

At 02:46 PM 9/16/2006, you wrote:
>Sorry to ask again, but I didn't get any responses the first time.
>I'm just trying to hook up my Ethernut board with a modem (ActionTec
>56K external modem), and I'm not having any luck. I have tried both
>null-modem and straight-through cables and haven't been able to get
>the NutChat function to do anything except timeout. I'm using:
>
>#define PPPCHAT     "'' AT OK ATD13106511000 CONNECT"
>
>and I'm using UART1 for stdout, and UART0 for the modem.
>
>Any tips or tricks or advice? I think I should be using a null modem
>cable, but perhaps not.

I am not familiar with the details of the board, but normally a CPU board 
is wired to be a DTE.  The modem is a DCE and RS-232 is designed to connect 
these two devices with a straight through cable.  It is when you want to 
connect a DTE to a DTE that you need the null-modem cable.  In fact, that 
is why it is called a null-modem; it looks the same as two modems 
connecting the two DTEs, but there is no actual modem, hence "null" modem!

If you want to take smaller steps, you can verify that the board and 
software are working by connecting pin 2 and 3 together on the CPU 
connector and see if it gets an echo of what ever it sends.  Then when this 
is working, you can send commands to the actual modem.