Electronics Design

Week 7

Introduction

This week assignment is to use the test equipment in my lab to observe the operation of a microcontroller circuit board, and to redo the echo-hello-world board and add some extra components.

Test Equipment

To test the connection on the circuit board I use an Ohm-meter with sound on. For signal testing I use an digital oscilloscope. The signals are very short, you need to play around with the oscilloscope settings. A good clue was to use the SINGLE mode.

Hello World Board

Based on the tutorial of Bas in Reykjavík I create the traces for the hello-world board I use the Eagle 8.6.3 premium version. Using Eagle I draw the schematic and processed the board (See Figure 1). To the original board I add a button and a led with a resistor in serial. The size of the resistor is 499 Ohm, I did not make any calculations of this size.
The traces was export as a black and white png file. The outlines was re-paint in GIMP and then export as a b/w png file. I use a SRM-20 Roland to mill out the PCB (See Mill a PCB using mods). For the traces I use a 1/64" SE 2FL, and for the outline I use a 1/32" SE 2FL drill.
From Useful files (see link at the end of this page) you can open the board file and check the design rules.

Figure1a — *Figure 1. Using the Eagle software to draw the hello-world board. Left: Schematic. Right: Board design.*

Figure1b — *Figure 1. Using the Eagle software to draw the hello-world board. Left: Schematic. Right: Board design.*

Figure2a — *Figure 2. Left: The hello board after the cut. Right: The result of the soldering. (Note the 6 pins headers are missing)*

Figure2b — *Figure 2. Left: The hello board after the cut. Right: The result of the soldering. (Note the 6 pins headers are missing)*

Unfortunately, I have no headings (2x3 pins or 1x6 pins) so I have to wait to program the board.
BREAK and continue.
I have finished the board (See Figure 3).

*Figure 3. The final(almost) hello board.*

I use the ISP 44 and Ubunto. to set the board, but for the final programming I use the Arduino software.
I run the Echo test using python term.py and in addition I used the PuTTy program in Windows, both programs work with success. I add a led and a button. I was able to program the light as I but the button shows unstable voltage. The header was a bit lose, so I decided to make a re-soldering, and that was the end of that board.
The Arduino code:

const int ledPin=3;
int timediff =100;
void setup() {
pinMode(ledPin, OUTPUT);
}

void loop() {
digitalWrite(ledPin,HIGH);
delay(timediff);
digitalWrite(ledPin,LOW);
delay(timediff);
}

Hopefully I will test the board next time I solder it, using the laboratory equipment (Now this is done, See week 9 Embedded programming).