Keyboard: Palm serial keyboard USB converter (#4485)

* Initial palm_usb support

* removing left over sun .c file

* fixing licenses

* actually adding updated files

* fixing build error

* more include cleanup

1 files changed, 96 insertions, 0 deletions

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+# Stowaway Serial keyboard  to USB  protocol converter
+
+A converter for Palm Pilot era Stowaway serial keyboards. 
+
+Makes extensive use of the code from [cy384](https://github.com/cy384/ppk_usb). Ported to QMK by [milestogo](https://github.com/milestogo).
+
+Hardware Supported: See hardware section below  
+Hardware Availability: self-built
+
+Make example for this keyboard (after setting up your build environment):
+
+    make converter/palm_usb/stowaway:default
+
+See the [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) and the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information. Brand new to QMK? Start with our [Complete Newbs Guide](https://docs.qmk.fm/#/newbs).
+
+
+## Hardware
+
+Target MCU is ATMega32u4 but other USB capable AVRs should also work. 
+
+cy843 has a very specific way of wiring in order to fit all pins in sequence. It breaks
+qmk because  the Arduino softserial library uses different pins from QMK. 
+
+I've wired the pro micro  hardware as follows. 
+
+Label| TX0,RX1,GND,GND,2  ,3  ,4  ,5  ,6  ,7
+Palm |    ,   , * ,GND,VCC,RX ,NC ,RTS,nc ,DCD
+MCU  |                ,D1 ,D0 ,   ,C6 ,   ,E6
+
+\* The RX line from the keyboard should be conected to a ~10K ohm pull down resistor to ground.
+RX --|--3
+    10K
+     |
+    GND
+
+
+Power management is not implemented yet, this just reboots the keyboard frequently. 
+
+### Keyboards: 
+
+Think Outside Stowaway Keyboards
+There are at least 5 different versions of these keyboards out there. 
+
+Group 1: Palm 3, Palm 5 & HP Journada 540, and Compaq iPaq keyboards. These share
+the same RTS protocol, but with different pinouts for each device. 
+
+Group 2: Handspring keyboards. These don't do handshaking protocol, and use TTL signal. 
+Set HANDSPRING to 1 in config.h
+
+Group 3: IRDA models. Untested but theoretically serial.
+
+### Connectors
+
+See https://github.com/cy384/ppk_usb for wiring & sample 3d printable sockets.
+
+Only Palm3 wiring has been tested.  
+RXD pin is output from keyboard to MCU's RX. 
+
+Viewed from left to right with the keyboard in typing position. 
+
+Palm3: [NC, VCC, RXD, RTS, NC, NC, DCD, NC, NC, GND]
+Palm5: [NC, VCC, RXD, RTS, NC, NC, DCD, NC, NC, GND] (same order, different connector)
+Handspring: [VCC/TXD, NC, NC, NC, GND, NC, NC, RXD]
+Journada: [NC, NC, NC, GND, NC, RTS, NC, DTR/VCC, RXD, DCD, NC]   [GND-IN, VCC-IN]
+Ipaq:  [NC, NC, DTR/VCC, NC, NC, RTS, NC, RXD, DCD, GND, NC, NC]
+
+### Protocol
+
+    Signal: Asynchronous, Negative logic, 9600baud, No Flow control
+    Frame format: 1-Start bit, 8-Data bits, No-Parity, 1-Stop bit
+
+    AVR USART engine expects positive logic while stowaway keyboard signal is negative.
+    To use AVR UART engine you need external inverter in front of RX and TX pin.
+    Otherwise you can software serial routine to communicate the keyboard.
+
+This converter uses software method, you doesn't need any inverter part.
+
+
+Commands From System To Keyboard
+    none
+
+Commands From Keyboard To System
+
+    0xFA Reset/Ready Response(followed by 0xFD)
+     
+References
+
+* http://www.splorp.com/pdf/stowawayhwref.pdf
+
+### Todo
+- Test on anything but a palm 3 model keyboard. 
+- Change all of the soft serial to match the new Helix based code so that it is easier
+to switch pins. 
+- The driver should check for a keyboard that pressed the delete key then disconnected. 
+Check every MAXDROP scans that the keyboard is there, and if not, clear the matrix. 
+Not implemented yet, since matrix scan is so much faster than serial.