[NTLK] NewtonTalk Digest, Vol 144, Issue 16

[Helmut Fischer]

Hello,

I am not sure whether you are aware of the difference between the formerly very common RS232 connections, most probably also used by your camera, and the RS424 standard Apple used for Macs and Newtons (should be covered in the FAQ, but I didn’t check).

RS232 used negative polarity (vs. ground) for the signals, the standard was 12 to 15 V, but most devices accepted TTL level (5 V).

RS424 has differential, potential-free, in- and outputs.

So, it was necessary to connect the Rxd+ and Txd+ pins at the Apple side to ground and to connect the Rxd- and Txd- pins to Tx and Rx at the RS232 side.

Maybe that helps?

Happy New Year everyone!

Helmut

> Am 30.12.2025 um 21:00 schrieb newtontalk-request at newtontalk.net:
> 
> Message: 2
> Date: Mon, 29 Dec 2025 15:48:42 -0500
> From: Noah Leon <moosefuel at gmail.com>
> To: newton Liste Newton Talk US <newtontalk at newtontalk.net>
> Subject: Re: [NTLK] Tibet
> Message-ID: <ADD12C6D-DEB1-485B-9934-1B05EBD06969 at gmail.com>
> Content-Type: text/plain; charset=utf-8
> 
> It occurs to me that the Newt might actually support TTL connections, since the Newton keyboard is apparently TTL (see this link: https://jimandnoreen.com/?p=259) so I wonder if I just wired it up for TTL rather than for serial if that would simply work? Just gotta try it I guess!
> 
>> see if it?s TTL voltages, 
>