Create README.md

README.md

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+# TashTalk
+
+## Elevator Pitch
+
+It's a LocalTalk interface, contained entirely within a single Microchip PIC12F1840 (8 pins, ~$1.50) microcontroller.
+
+It handles all the time-sensitive aspects of LocalTalk, bidirectionally bitbanging the SDLC and FM0 (a.k.a. differential
+Manchester) based protocol at the data link and physical layers, sending and responding to control frames with CRC
+calculation and checking, and collision avoidance and retransmission. It can also respond to any number/combination of
+node IDs for use in bridging applications. It can be interfaced directly to user-mode software on a Raspberry Pi or 
+BeagleBone or full PC, or it can be part of a larger embedded system. It slices, it dices, etc.
+
+
+## Project Status
+
+Stable.  
+
+
+## Caveats
+
+Because of the PIC12F1840's limited memory and the way its UART is used, the host's UART needs to be able to handle a baud
+rate of 1 Mbps. Conventional UARTs don't expect to be pushed beyond 115.2 kbps. In addition, the PIC has a 128-byte receiver
+queue, which is considerably smaller than the largest possible LocalTalk frame (605 bytes). As such, the host needs to respect
+when the CTS hardware flow control line is deasserted so the queue doesn't overflow and be quick about resuming transmission
+when CTS is reasserted so the queue doesn't underflow either.
+
+Also, "single-chip" doesn't include the separate and necessary driver/receiver chip for RS-422/485. Sorry. =)
+
+
+## Projects Using It
+
+* [TashTalkHat](https://68kmla.org/bb/index.php?threads/tashtalk-single-chip-localtalk-interface.38955/page-4#post-422138)
+  by bdurbrow - hat for Raspberry Pi
+* [AirTalk](https://68kmla.org/bb/index.php?threads/introducing-and-interest-check-airtalk-wireless-plug-and-play-localtalk-dongles.39661/)
+  by cheesestraws - wireless plug-and-play LocalTalk dongle
+* Yours? =)