Week 09

* Probe an input device(s)'s analog levels and digital signals.
* Document your work to the group work page and reflect on your individual page what you learned.

* Measure something: add a sensor to a microcontroller board that you have designed and read it.

☑ Linked to the group assignment page.
☑ Documented what you learned from interfacing an input device(s) to your microcontroller and optionally, how the physical property relates to the measured results.
☑ Documented your design and fabrication process or linked to the board you made in a previous assignment.
☑ Explained the programming process(es) you used.
☑ Explained any problems you encountered and how you fixed them.
☑ Included original design files and source code.
☑ Included a ‘hero shot’ of your board.

Before I go into this week weekly assignment, I was trying to relate this week's topic to my final project. But all the input sensors that I need was just a series of normal button switches. So I am decided to take this chance to learn something about "Step Response".
According to Deepseek AI platform,


In short, The step-response is a sensor that is made with two sheets of copper, separated from each other by a porous insulating material. It can be used to calculate the value of force, weight, resistance ... I have followed Robert Hart's tutorial
A series of pulses is sent through the TX electrode, which, depending on the material between the two electrodes, allows more or less that series of pulses to pass. In the following graph you can see how it works. The other electrode will be connected between two resistors, one for pull-up and the other for pull-down and to an analog input.

Creating A Step Response Module

Since this was just an additional module, I need not to go to Autodesk EAGLE software to prepare my board. Instead, I just go edit the file that I referred to (credit to Neil's lecture notes) and use GIMP software to edit.

Here is the final PNG file that I have prepared for the additional module.
.
After having both PNG files for tracing process and milling process, I am going to prepare the G-Code files using MODs.


And here is how my add-on module for step response looks like after finish milling from StepCraft CNC machine.

Steps to test my Step Response Module

Firstly, I am going to solder a 1x5 header pin to my add-on step response module, so that I am able to direct connect with my own PCB through 4 dupont cables.

Up next, before uploading a program to test my board, I need to set up my cable connections (3 signal pins - A0, A1 and A2 and 1 GND) in order to link up.

Lastly, I refer to my instructor - Mr. Steven Chew's Touch Analog Program to test on my own setup.

This program will show different RGB light on my PCB - RED (220, 0, 0), GREEN (0, 220, 0) and BLUE (0, 0, 220) when I touches different pads.

The important setting to light up the LED on the SEEED XIAO RP2040 micro-controller is the THRESHOLD value. This value defines the point that the INPUT signal is HIGH to toggle the LED to light up. For my case, I set to 200.

In the video, when my finger touches both RED pad with GND, the LED will show RED light. Likewise, when my finger touches both GREEN pad and GND and both BLUE pad and GND, it will show GREEN and BLUE light respectively. I go abit further by touching both RED pad, GREEN pad and GND and both GREEN pad, BLUE pad and GND, the LED will show YELLOW and CYAN respectively. In the end of the test. I toughes ALL the pads and the LED shows BRIGHT WHITE light.

Reflection

It is been a tough week for me, as I myself not good in this field - Electrical and Electronic. Just for the Tx - Rx segment and Charge up and discharge sections has been a nightmare for me at least for a few nights. But I need to get myself buck up and clear the application, so that I can apply to my final project, as I am planning to toggle my musical box's functions by using touch pad as my input device.