[NTLK] USB to Newton Interconnect cables

[Anthony Morrow]

On Feb 5, 2016, at 6:39 PM, davida at pobox.com wrote:

> That’s actually one area I suspect I should prototype thoroughly.
> 
> There are two serial ports on the Interconnect port: one using a Linear Technologies LT1323 line driver, one with raw CMOS levels.  The default port is SCC channel 0, which has the line drivers, and I’m kinda tempted to use that because it avoids the need for a package on the Newt to enable the second port (SCC Channel 3).
> 
> The Interconnect doc from Apple states that the drivers on channel 0 use RS422 signalling.  I’ve grabbed a copy of the LT1323 datasheet, but haven’t had a chance to read it in detail yet, but … it might then be best to use an RS-422 driver from the USB bridge, rather than an RS-232 driver.  The MAX driver is the default part here, but I haven’t looked at its datasheet yet either.
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> So .. you’re absolutely correct to highlight this as an issue with the design.  Once I’ve perused the datasheets, I’ll come up with a proposal, and run it past the group for comment before doing a prototype to test it out for real.
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> d

My brain is foggy on this subject, but I remember connecting my Newton 2100 to a PC to sync Outlook items using only a interconnect-to-DB-9 cable. Would that had been using RS-232 since it was a PC instead of RS-422 seen in old Macs?


Update before I sent this. Someone wrote on the wiki page for RS-422 that Apple used a variant that was compatible with RS-232. Maybe that is why the Newton worked with PCs over serial. <https://en.wikipedia.org/wiki/RS-422>.

-Tony Morrow