udpate readme to reflect QMK and not having the Makefile from ahtn's repo

keyboards/lets_split/readme.md

@@ -6,9 +6,45 @@ This readme and most of the code are from https://github.com/ahtn/tmk_keyboard/
 Split keyboard firmware for Arduino Pro Micro or other ATmega32u4
 based boards.
 
+
+## First Time Setup
+
+Download or clone the whole firmware and navigate to the keyboards/lets_split directory. Once your dev env is setup, you'll be able to generate the default .hex using:
+
+```
+$ make rev2
+```
+
+You will see a lot of output and if everything worked correctly you will see the built hex files:
+
+```
+lets_split_rev2_serial.hex
+lets_split_rev2_i2c.hex
+```
+
+If you would like to use one of the alternative keymaps, or create your own, copy one of the existing [keymaps](keymaps/) and run make like so:
+
+
+```
+$ make rev2-YOUR_KEYMAP_NAME
+```
+
+If everything worked correctly you will see a file:
+
+```
+lets_split_rev2_YOUR_KEYMAP_NAME.hex
+```
+
+For more information on customizing keymaps, take a look at the primary documentation for [Customizing Your Keymap](/readme.md##customizing-your-keymap) in the main readme.md.
+
+### Let's split 1.0
+If you have a first generation Let's Split you will need to use the revision 1 code. To do so, use `rev1` in all your commands instead.
+
 Features
 --------
 
+For the full Quantum Mechanical Keyboard feature list, see [the parent readme.md](/readme.md).
+
 Some features supported by the firmware:
 
 * Either half can connect to the computer via USB, or both halves can be used
@@ -62,7 +98,7 @@ unnecessary in simple use cases.
 Notes on Software Configuration
 -------------------------------
 
-Configuring the firmware is similar to any other TMK project. One thing
+Configuring the firmware is similar to any other QMK project. One thing
 to note is that `MATIX_ROWS` in `config.h` is the total number of rows between
 the two halves, i.e. if your split keyboard has 4 rows in each half, then
 `MATRIX_ROWS=8`.
@@ -70,37 +106,59 @@ the two halves, i.e. if your split keyboard has 4 rows in each half, then
 Also the current implementation assumes a maximum of 8 columns, but it would
 not be very difficult to adapt it to support more if required.
 
-
 Flashing
---------
+-------
-
 From the keymap directory run `make SUBPROJECT-KEYMAP-avrdude` for automatic serial port resolution and flashing.
-
 Example: `make rev2-serial-avrdude`
 
+
+Choosing which board to plug the USB cable into (choosing Master)
+--------
+Because the two boards are identical, the firmware has logic to differentiate the left and right board.
+
+It uses two strategies to figure things out: look at the EEPROM (memory on the chip) or looks if the current board has the usb cable.
+
+The EEPROM approach requires additional setup (flashing the eeeprom) but allows you to swap the usb cable to either side.
+
+The USB cable approach is easier to setup and if you just want the usb cable on the left board, you do not need to do anything extra.
+
+### Setting the left hand as master
+If you always plug the usb cable into the left board, nothing extra is needed as this is the default. Comment out `EE_HANDS` and comment out `I2C_MASTER_RIGHT` if for some reason it was set.
+
+### Setting the right hand as master
+If you always plug the usb cable into the right board, add an extra flag to your `config.h`
+```
+ #define I2C_MASTER_RIGHT
+```
+
+### Setting EE_hands to use either hands as master
 If you define `EE_HANDS` in your `config.h`, you will need to set the
-EEPROM for the left and right halves. The EEPROM is used to store whether the
+EEPROM for the left and right halves.
+
+The EEPROM is used to store whether the
 half is left handed or right handed. This makes it so that the same firmware
 file will run on both hands instead of having to flash left and right handed
 versions of the firmware to each half. To flash the EEPROM file for the left
 half run:
 ```
-make eeprom-left
+avrdude -p atmega32u4 -P $(COM_PORT) -c avr109 -U eeprom:w:eeprom-lefthand.eep
+// or the equivalent in dfu-programmer
+
 ```
 and similarly for right half
 ```
-make eeprom-right
+avrdude -p atmega32u4 -P $(COM_PORT) -c avr109 -U eeprom:w:eeprom-righhand.eep
+// or the equivalent in dfu-programmer
 ```
 
-After you have flashed the EEPROM for the first time, you then need to program
+NOTE: replace `$(COM_PORT)` with the port of your device (e.g. `/dev/ttyACM0`)
-the flash memory:
+
-```
+After you have flashed the EEPROM, you then need to set `EE_HANDS` in your config.h, rebuild the hex files and reflash.
-make program
+
-```
 Note that you need to program both halves, but you have the option of using
 different keymaps for each half. You could program the left half with a QWERTY
-layout and the right half with a Colemak layout. Then if you connect the left
+layout and the right half with a Colemak layout using bootmagic's default layout option.
-half to a computer by USB the keyboard will use QWERTY and Colemak when the
+Then if you connect the left half to a computer by USB the keyboard will use QWERTY and Colemak when the
 right half is connected.