Jose Alegria - Fab Academy

Electronics Design

Assignment

wHAT iS THE ASSIGNMENT ABOUT?

Redraw one of the echo hello-world boards or something equivalent, add (at least) a button and LED (with current-limiting resistor) or equivalent input and output, check the design rules, make it, test it. Optionally, simulate its operation.

GROUP ASSIGNMENT:

Use the test equipment in your lab to observe the operation of a microcontroller circuit board.

What did I learn:

- The most important part of electronics production is electronics design.

- There are a few options to make the design, this is the simplest part. Once you get used to design in the chosen software the process is straightforward.

- The difficult part is to connect all the pins, ports, and pads correctly and getting to know the function of each one of those.

1^st Step. Getting a design

For this assignment we are not making a board from scratch. So, I used the board that Adrian Torres (Leon, 2020) uses as a SAMDINO, to have a starting point and proceed with the modifications needed.

This is the board I will be modifying:

2^nd Step. Modifying the board

To modify the board, I used the Eagle module embedded within Fusion 360. I made a list of the components needed according to the first board, and then added the components needed to install two sets of button and LED. The first one using the microprocessors internal resistor and a second one using an external resistor.

Description	Part	Value	Device	Package	Qty.
Capacitor 1 micro F	C1	1uF	CAP_UNPOLARIZEDFAB	C1206FAB	2
Regulator 3.3 V	IC1		VR_REGULATOR-SOT23SOT23	SOT23	1
Regulator 5 V	LM2940	VR_REGULATOR_SOT223	VR_REGULATOR_SOT223	SOT223	1
Resistor 100 K	R1	100 K	RES-US1206FAB	R1206FAB	1
Resistor 0	R2	0	R1206FAB	R1206FAB	2
Resistor 1 K	R3	1K	R1206FAB	R1206FAB	2
Resistor (US Symbol)	R7	10K	R1206FAB	R1206FAB	1
Button 6 mm	S1		6MM_SWITCH6MM_SWITCH	6MM_SWITCH	2
LED	U$2	LEDFAB1206	LEDFAB1206	LED1206FAB	2
Programming Pin 2x2	U$1	PINHD-2X2-SMD	PINHD-2X2-SMD	2X02SMD	1
Microprocessor	U1	ATSAMD11C14A-SSUT	ATSAMD11C14A-SSUT	SOIC14_SL_MCH	1
USB Connectors	X1	CONN_USBPCB	CONN_USBPCB	USB-A-PCB	1

I changed some of the component’s footprints to the ones in the Fabacademy Library to get bigger footprints that are easier to fix to.

Then, the next step was to create a board schematic with all the connections needed for the board to work.

This is the result:

At last, I had to locate all components in the PCB Board and make the routes needed to connect them.

To make the new routes I followed a few design rules such as:

1. Minimum wire width: 24 mil (made this way to avoid wire breaking up)

2. Clearance: 16 mil (this is the tool diameter)

This design rules that I followed by myself had to be set into the program in a toolbox called DRC, to get there you should go to the upper bar, select the DRC / ERC tab, and click in the DRC button (or press Alt + F4).

There you can set the different rules which will be followed as a preset when you design, although they can be overrun if needed for your design. Due to this possibility, you can make mistakes that will lead to certain design flaws within your board: wires being too thin, small clearances that difficult the wielding of components or wires being too close to the board limits.

So, if you want to know beforehand if you have made this mistakes, there is an Error check button that will display the problems within your design, then you can decide whether or not they are allowable.

For example, in my design there were some design errors displayed when using this feature, there were a couple of wires too close to the board limit, but once I checked them out, they were the USB connector pads and it was part of the design I needed, so I disregarded them.

Finally, exporting them to png files that will be readable by the Mods Program:

3^rd step. Electronics production

To send the milling and cutting files to the machine we used a different method than the one used during the group assignment. Now, the computer was directly sending the file to the machine from mods, and we did not used the processor program. The parameters where the same that we were using before.

Here are the parameters I used for milling:

- Tool Diameter: 0.0156 in

- Cut depth: 0.004 in

- Max depth: 0.004 in

- Offset number: 6 (used this to create a cleaner area to work with even though it needs more time to be done)

- Speed: 2 mm/s

And these are the parameters I used to cut:

- Tool Diameter: 0.0625 in

- Cut depth: 0.024 in

- Max depth: 0.072 in (made in 3 steps)

- Speed: 3 mm/s

Finally, after a few tries, getting the work done correctly. Next step is to fix the components and set up the board for programming. This is how it looked like after fixing everything in place.

4^th step. Programming

For this stage I had to create a programmer board used exclusively for programming my different boards I was going to use for the different assignments. This was also created from Adrian Torres SAMDINO page, and programmed with EDBG as follows (Windows):

- Download EDBG software to the PC in any folder, it is in: https://github.com/ataradov/edbg

- Download EDBG Free Dap Bootloader file and save it in the EDBG folder.

- Open Terminal.

- Go to EDBG Folder.

- Type the next command: << edbg-windows-r38.exe -b -t samd11 -epv -f free_dap_d11c_mini.bin >>.

- If everything is plugged in correctly and working your board is now a free dap programmer.

This works to only to create a programmer board. Next, I had to program my new board. For that we need to download a bin file for a SAMD11C14A from Mattairtech page. Save it to the EDGB Folder, open Terminal and go to EDBG Folder. Type the following command: << edbg-windows-r38.exe -b -t samd11 -epv -f sam_ba_SAMD11C14A.bin >>.

Now we should download the Arduino IDE and change a few parameters to let it control our board:

- Open Arduino IDE.

- Open Preferences

- Open Additional Boards Manager URLs and type: << https://www.mattairtech.com/software/arduino/package_MattairTech_index.json >>

- Go to Tools - Board Manager and install the Generic D11 board Manager:

After this, you will be able to use your board as an Arduino Board for programming purposes.

To test the board I uploaded a << BlinkWithoutDelay >> program that I found within the Arduino precharged files.

Conclussions

This assignment importance was to learn how to modify the existing schematics to take advantage of the work that already has been done within the FabAcademy universe. We must have an understanding of what do we need and how this components work to be able to modify them.

Original Files

1. Original Files (f3z, brd, sch, png)

Nueval Checklist

- Linked to the group assignment page.

- Documented what you have learned in electronics design.

- Explained problems and how you fixed them.

- Included original design files.

- Included a hero shot of your board.

- Loaded a program and tested if your board works.

2022