Add figure descriptions

docs/group_assignments/group2/assignment4.md

@@ -26,24 +26,39 @@ as each one of us did one microcontroller.
 
 We used these "ring oscillator" codes from Neil:
 
-* [rp2040 code](https://pub.pages.cba.mit.edu/ring/GPIO/RP2040/ring.RP2040.ino)
+* [RP2040 code](https://pub.pages.cba.mit.edu/ring/GPIO/RP2040/ring.RP2040.ino)
 
-* [esp32C3 code](https://pub.pages.cba.mit.edu/ring/GPIO/ESP32/ring.ESP32C3.ino)
+* [ESP32C3 code](https://pub.pages.cba.mit.edu/ring/GPIO/ESP32/ring.ESP32C3.ino)
 
-* [samd21 code](https://pub.pages.cba.mit.edu/ring/GPIO/SAMD11C/ring.D11C.ino)
+* [SAMD21 code](https://pub.pages.cba.mit.edu/ring/GPIO/SAMD11C/ring.D11C.ino)
 
 ## Pin connections
 
 We first soldered microcontrollers (XIAO RP2040, XIAO ESP32C3, and XIAO SAMD21 with pin connectors. Then, we were smoothly able to plug it into the breadboard for a group assignment with ring oscillators.
 
+![Measurementphoto](./assets/assignment4/schematic_photos/mikrocontrolledRP_soldered.jpg)
+Figure: Example of a microcontroller board with soldered pin connectors.
+
 The idea is to connect one input and one output pin together. In the programmed code the input will be read and the output will be set to the opposite boolean value.
 This will result in a square wave of which frequency we will measure with the oscilloscope.
 
-[rp2040 schematic](https://files.seeedstudio.com/wiki/XIAO-RP2040/res/rp2040_datasheet.pdf)
+### XIAO RP2040
+
+[RP2040 schematic](https://files.seeedstudio.com/wiki/XIAO-RP2040/res/rp2040_datasheet.pdf)
+
+### XIAO ESP32C3
+
+[ESP32C3 schematic](https://files.seeedstudio.com/wiki/XIAO_WiFi/Resources/Seeeduino-XIAO-ESP32C3-SCH.pdf)
 
-[esp32C3 schematic](https://files.seeedstudio.com/wiki/XIAO_WiFi/Resources/Seeeduino-XIAO-ESP32C3-SCH.pdf)
+### XIAO SAMD21
+
+The code for this was not presumably specifically for the SAMD21 but an earlier model.
+Therefore, there wasn't direct instructions on which pins to connect.
+From the rather complex looking C code we were able to figure out that the pins used were
+PA02 and PA04 which we found from the schematic.
+
+[SAMD21 schematic](https://files.seeedstudio.com/wiki/Seeeduino-XIAO/res/Seeeduino-XIAO-v1.0-SCH-191112.pdf)
 
-[samd21 schematic](https://files.seeedstudio.com/wiki/Seeeduino-XIAO/res/Seeeduino-XIAO-v1.0-SCH-191112.pdf)
 
 
 ## Measurements 
@@ -52,11 +67,8 @@ We used Keysight InfiniiVision DSOX3102A, a digital storage oscilloscope to meas
 
 ### Images of the procedure
 
-The following figures (Figures 1, 2, 3) show schematics of the connection between the programmed microcontroller and oscilloscope.
+The following figures show how made the connection between the programmed microcontroller and oscilloscope.
 
-The following figures (Figures 4, 5, and 6) show measurements at the oscilloscope.
-
-![Measurementphoto](./assets/assignment4/schematic_photos/mikrocontrolledRP_soldered.jpg)
 
 ![Measurementphoto](./assets/assignment4/schematic_photos/ESP32C3.jpg)
 
@@ -70,11 +82,16 @@ The following figures (Figures 4, 5, and 6) show measurements at the oscilloscop
 
 ### Results
 
+The following figures show measurements from the oscilloscope.
+
 ![oscilloscope measurement](./assets/assignment4/oscilloscope/RP2040.png)
+Figure: XIAO RP2040 measurements
 
 ![oscilloscope measurement](./assets/assignment4/oscilloscope/ESP32C3.png)
+Figure: XIAO ESP32C3 measurements
 
 ![oscilloscope measurement](./assets/assignment4/oscilloscope/SAMD21.png)
+Figure: XIAO SAMD2 measurements
 
 The signal frequencies for 
 XIAO RP2040, XIAO ESP32C3, and XIAO SAMD2 are