[NTLK] MP2x00 Internal Interconnect Breakout

Matthias Melcher mm at matthiasm.com
Tue Jan 13 17:38:44 EST 2015

Based on this EMail thread, I have found a mix of *really* nice chips that I want to use to build another (better) USB interconnect for the internal port.

I will not use one of the dumb USB-to-RS232 converters, but instead use an LPC1347 CPU, which incidentally costs the same, but comes with an ARM Cortex MCU core running at 72 MHz. It has more than enough pins to connect to every pin on the connector, and more (much more) than enough power to handle USB and Ser1.

It has *one* feature that made it my favorite: it can be programmed through the USB port alone without any special software. So if I should be able to build a board for regular users (aiming at 50 Euros), any user can easily upgrade the firmware at home. So even if I don't get that thing right from the beginning, we can still fine-tune later.

The key features:

 - physically add a USB port where the Modem port was planned (no filing or drilling required)
 - use Ser1 in a compatible way, not blocking the external port if no USB connection
 - no extra software needed on the MessagePad. It just works.
 - full support for debugging
 - fixing the timing bug that requires slowdown.exe on MSWindows

Now for the convenience part:

 - charging the battery via USB should be possible if enough power is available

And finally for the crazy part. We have access to the otherwise unused serial port 3, so why not use it and add some functionality? 

So here are some dreams. Feel free to add if you have ideas!

Serial Port 3 can be accessed using one of the terminal programs on the MP. Using the terminal, the MP can communicate with the ARM Cortex card, just as if it was an external PC or Modem.

The ARM Cortex can then very easily provide a command prompt interface, just like an FTP server. Heck, it *could* actually *be* an FTP or Web Server. The MessagePad would think that there was a modem, again requiring no new software.

Now, there is plenty of space in the box. Why not add a MicroSD card. Todays MicroSD cards are so huge in capacity that they can easily hold every .pkg ever created for the MessagePad. The SD card could be browsed with any Newton web browser, and the packages could be installed right from the SD card.

This would work the other way around as well. The Cortex can pretend to be a PC, and the user can store system backups on the SD card and export data to it without ever connecting to a PC.

To the outside world, the Cortex can pretend to be a memory card, giving access to the internal SD card from any PC that is connected to the USB port.

Dreaming crazy dreams ;-)

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