Using an FRC with the RCX?

[Gabriel]

I know that its probably more fun to reverse-engineer it, but have you guys thought about talking to LEGO for the specs? I know that they sponsor team 96 and I think their mindstorms engineers work with them.

[Astronouth7303]

Why? all the reverse-engineering and spec-finding has been done for us. The most reverse-engineering I've done yet is putting a continuity tester to the original gray cable! And RS-232 has been standardized to death, so it's the easiest protocal to use (at either end!).

[Astronouth7303]

The TTL port uses the same transmission format as RS-232 (low start bit, 8 data bits, high stop bit). So if you take a 3-pin cable and attach it the Tx, Rx, and Gnd pins on a DB9 female connector, you can use TTL port instead of the prog port. The macro would need to be changed slightly.

Odd, ifi_utilities.c and printf_lib.c both use 'TXREG', but ifi_picdefs.h defines 'TXREG1' and 'TXREG2'.

[Ryan M.]

Originally Posted by Astronouth7303

The TTL port uses the same transmission format as RS-232 (low start bit, 8 data bits, high stop bit). So if you take a 3-pin cable and attach it the Tx, Rx, and Gnd pins on a DB9 female connector, you can use TTL port instead of the prog port. The macro would need to be changed slightly.

Odd, ifi_utilities.c and printf_lib.c both use 'TXREG', but ifi_picdefs.h defines 'TXREG1' and 'TXREG2'.

If you think it'll work, go for it.

[Astronouth7303]

Use this cable for connecting to the LIRT:

LIRT  TTL/Dig
DB9F  1x3 Connectors (2x)
  Tx  TTL.Rx
  Rx  TTL.Tx
 Gnd  TTL.Gnd
 RTS  Dig.Sig
 CTS Dig.Gnd

In the LIRT, the RTS and CTS pins are jumpered. Use the Digital connector to find out if the tower is connected (high when it is, low when isn't. So FALSE is CONNECTED, and TRUE is NOT CONNECTED)
The Pin Equivalents are:

3	TTL.Red
2	TTL.White
5	TTL.Black
7	Dig.White
8	Dig.Black

This is relative to the Male connector, so double check. You need to use a FEMALE connector. I believe you just switch Tx and Rx (RTS and CTS doesn't matter in this case: a jumper's a jumper)

Specific info on what to send can be found in the Mindstorms SDK. (Use v1.5 I believe)