The theme of this week was "Electronic Production", which provides tools that let us start from making a printed circuit board with a milling machine and soldering the components; to load firmware and test its operation.

Previous experiences

As part of a disguise, a few years ago I made an "Arc Reactor". My first attempt was very rudimentary, only LEDs connected to a switch and some batteries. The light emitted was very strong, but it did not last long, the LEDs began to burn. Because of this experience, I learned that the LEDs must always be protected by a resistance. In the second version, I had the adequate resistance to the voltage, and put everything on a PCB board, for that I used the "home" method of transfer by ironing. Already encouraged by the success of this experiment, I decided to do more details. In these images you can see the result.

I chose to manufacture the FabISP "hello.ISP.44.res", which is a programmer for AVR microcontrollers. I will use it to program other PCBs that I will do in the next assignments.
Board
Traces
Interior

I worked with the Roland's "Modela MDX-20" milling machine. This machine is composed of a mandrel that moves in a carriage from left to right and top to bottom, a board to hold the PCB board that moves from front to back and a command panel. In these images we can see the milling machine and the main parts.

The manufacturing process of the PCB in the milling machine will be done in two parts:

• Recording of tracks with 1/64" cutter
• PCB board cut with 1/32" cutter

The cutter must be adjusted on the mandrel using an Allen key. This operation must be done with the router turned off. We must be very careful not to break the tip that is very thin.

On the computer that is connected to the milling machine, open the milling program with the "sudo fab" command.

Then, we must select the file with the strokes for the engraving of the tracks.
Choose "mill traces (1/64)" for the recording of the tracks. For the case of cutting it is recommended to choose "cut out (1/32)". Also, the tolerance parameter must be changed to 0.1 error (pixels).

The (0,0) coordinates are in the lower left part both on the board and in the software. To prevent the plate from moving during milling, it must be glued with a double contact tape.

Before starting the milling, the height must be calibrated, for this press the view button so that the milling cutter is positioned in position 0,0. Then in the software enter the Xmin Ymin coordinates and press the "move to Xmin, Ymin" button and very carefully use the "UP" and "DOWN" buttons to bring the bit closer to the surface, it should stop as soon as you notice that they are produced shavings.

As a safety measure, the router only works with the plastic cover in place.

To start milling, click on the button "Send it!"

In this video, we can see part of the milling process

Once finished, turn off the router and remove the plastic cover to change the cutter. Here we can see the PCB board finished and ready for the next stage "Welding the electronic components".

The bill of materials is as follows:

• 1 ATTiny 44 microcontroller Data Sheet (IC1)
• 1 Capacitor 1µF (C1)
• 2 Resistor 100 Ω (R3, R4)
• 1 Resistor 499 Ω (R2)
• 1 Resistor 1K Ω (R1)
• 1 Resistor 10K Ω (R5)
• 1 6-pin header (J1 ISP)
• 1 USB connector (J2 USB)
• 2 jumpers - 0 ohm resistors (SJ1, SJ2)
• 1 Resonator 20MHz (20MHz)
• 2 Zener Diode 3.3V (D1, D2)
• 1 usb mini cable
• 1 ribbon cable
• 2 6-pin connectors

This is the location of the electronic components on the board.

Do not forget
Before starting to solder, the PCB should be cleaned very well, otherwise the soldering will not adhere to the copper surface. In the following image you can see my attempt to solder with the dirty PCB. It took me a long time.

All components must been solder in the following order:

1. Mini USB header
2. Microcontroller
3. Resonator
4. Diodes, be careful with their polarity
5. Resistances
6. Capacitors
7. Jumpers, and
8. 6pin programming header

Already prepared with everything necessary we started.

Then, we solder the Mini USB connector.
I did not get the mini usb connector for surface mounting, instead I used a micro usb. but to weld it it was necessary to bend the terminals a little.

Welding the microcontroller took me sometime.
I made a mistake putting solder points on the PCB before the microcontroller.
To fix it I should have used a desoldering wire, but at that time I only had a desoldering pump, I think I would have done it in less time with the desoldering wire.

The pieces are so small that you must use tweezers.
You must be careful with the pressure, because they can move during welding, as in this image, or they can jump and fell to the ground, also that happened to me, the microcontroller fell to the ground and I spent 5 minutes in finding it.
To fix the resistor wrong I used the soldering iron, some tweezers, patience and good pulse desolde and re-locate the resistor.

Once finished, we proceed to take it off the table.

Now, we are ready to start the programming of the new FabISP.

I did the "Smoke Test", I connected the card to the computer through the USB cable and did not detect anything ! ... something must be wrong welded.

I had already checked all the welds and the only one that can be wrong is the micro usb, since its terminals do not touch the copper surface.

I removed the micro usb connector by heating the contacts, but one of the brackets went out, I hope that with three the new connector can be held, otherwise I will have to redo everything.

Here we can see both micro and mini usb connectors, the connectors are different.

I secured the card and connector to a bracket without pressing too much and proceeded to weld the legs and connectors.

Here we can see the welded connector in its place.

Again I tried the USB connection and this time recognized the presence of a card. Now if we go to the programming phase of FabISP.

Before installing the software for AVR programming, we must identify the pins of the 2x3 pin header taking as reference the GND pin, otherwise we could connect the ISP connection cable backwards.

To program the FabISP I needed to install Avrdude. There is a version of AVRDUDE for Windows 10, but it is not reliable, it is best to install the bash of Ubuntu for Windows 10 and from there run Avrdude.

Here is the link with the explanation:
Ubuntu for windows 10.

To start the installation the BASH program is executed, this creates a session of Ubuntu in Windows 10.

To fix this I should update the ubuntu with the command:

sudo apt-get update

then asked for the user's password and started updating

Again I executed the command:

sudo apt-get install flex byacc bison gcc libusb-dev avrdude

Then the next command installed the gcc-avr package

sudo apt-get install gcc-avr

later, to install the avr-libc library I executed the command.

sudo apt-get install avr-libc

finally, I installed libc6-dev library.

sudo apt-get install libc6-dev

Well, apparently, it was already installed.

I changed to the firmware directory. then I edited the Makefile file.

next I compiled the firmware with the command

make clean

the next step was to compile the hexadecimal file with the command:

make hex

Out of curiosity, I ran the lsusb command to see the usb ports.

then I set the fuses to work with the internal clock with the command

make fuse

I got an error, ...sudo command is missing.

I tried again, but with the sudo command and readjusted the contacts.

sudo make fuse

Next, I programmed my FabISP to be an ISP with the command

make program

I got an error, this time it was intentional the omission of the sudo command.
I executed the command again

sudo make program

Conclusion: for security, the commands that modify information in a device must be executed with the rights of the super user.

I executed the lsusb command without connecting the FabISP and this is the result. Only the devices connected to the computer are displayed.

This time I connected the FabISP a USB port and executed the command lsusb.
I highlighted in yellow the row with the FabISP information.

To finish I retired the 0 ohm resistors.

As of this moment my FabISP has become a programmer card and is ready to use it with the next cards that I make.

Now from devices and printers in the Control Panel you can see the card fully identified.

Additionally
To protect my FabISP, with what I learned in "Computer-controlled cutting" , I made a little box