Updated Appendix E: Flashing a Bootloader (markdown)

Appendix-E:-Flashing-a-Bootloader.md

@@ -48,6 +48,8 @@ If the Arduino IDE reports that you successfully flashed the firmware onto the A
 
 ## Connect the programmer to the Ploopy PCB
 
+**This next bit is very tricky. Pay very close attention.**
+
 The Ploopy PCB ICSP header consists of six holes (or six pins, if you've added a connector). The pins are numbered like this:
 
 ```
@@ -58,6 +60,16 @@ The Ploopy PCB ICSP header consists of six holes (or six pins, if you've added a
 
 Note that pin 1 is a square pad on the board. Also, this is the way the header looks when viewed from the *top* of the board (i.e. when the microcontroller is visible). [Here's a picture of what it looks like](https://i.imgur.com/nh6e5tQ.jpg) **TODO fix this**.
 
+**HOWEVER.** On the Ploopy Nano PCB, the microcontroller actually covers these holes. You'll have to flip the PCB upside-down in order to access the ICSP header. Obviously, if it's upside-down, the header is backwards. So, really, the numbers are like this:
+
+```
+ 2 -> o  ■ <- 1
+ 4 -> o  o <- 3
+ 6 -> o  o <- 5
+```
+
+Got that?
+
 Hook up the ICSP connector on the Ploopy PCB to the programmer. If you're using an Arduino Nano, make the following connections:
 
 ```