Update README.md

Author: psobot

README.md

@@ -8,7 +8,12 @@ pip install arduino-coldfire-bdm
 
 ### Usage
 
-After running `pip install arduino-coldfire-bdm` on a machine with a working Python 3 installation, use the `arduino-coldfire-bdm` command-line program:
+1. Ensure you have a [working Python 3 installation](https://python.org/download).
+2. Run `pip install arduino-coldfire-bdm` on the command line to install this package.
+3. Connect an Arduino to a Motorola Coldfire via its debug pins. See [arduino-coldfire-bdm.ino](https://github.com/psobot/arduino-coldfire-bdm/blob/main/arduino_coldfire_bdm/arduino-coldfire-bdm.ino) for suggested pin mappings. (Ensure the Coldfire board is powered up independently; the Arduino does not supply power to the Coldfire.)
+4. Use [the Arduino IDE](https://arduino.cc/en/software) to compile and upload [arduino-coldfire-bdm.ino](https://github.com/psobot/arduino-coldfire-bdm/blob/main/arduino_coldfire_bdm/arduino-coldfire-bdm.ino) to your Arduino.
+    - Note that you may need to change the pin numbers at the top of the script depending on your Arduino and the pins you used to connect to the Coldfire.
+5. On the command line (Terminal.app, Command Prompt on Windows, etc), run `arduino-coldfire-bdm` (or, if that doesn't work, `python3 -m arduino_coldfire_bdm.command_line`) to invoke the command line program. You should see the following help text:
 
 ```
 usage: arduino-coldfire-bdm [-h] [--dry-run] [--show-commands] [--serial-port SERIAL_PORT] [--baud-rate BAUD_RATE] {dump_memory,trace_execution,load_flash,sram_test} ...
@@ -32,6 +37,8 @@ commands:
     sram_test           Test SRAM attached to the Coldfire. Expects exactly 1MB of RAM, attached via chip-select port 1, mapped at 0x00200000.
 ```
 
+6. Select the appropriate `--serial-port` to use to connect to your Arduino, and run one of the commands.
+
 ## What?
 
 A long long time ago (the mid-1990s), Motorola created a series of CPUs derived from the 68k architecture, called the Coldfire. These processors are largely obsolete today, but are still found in certain industrial equipment and embedded devices released around that time; including some vintage synthesizers, like [the Alesis A6 Andromeda](https://www.alesis.com/products/view/a6-andromeda).