Input Devices

Assignments

Group Assignment

• probe an input device's analog levels and digital signals

Individual Assignments

measure something: add a sensor to a microcontroller board that you have designed and read it

Group Assignment

Our group assignment which has been done with me, Antti and Kenichi can be found here here. We disassembled DHT11 humidity and temperature sensor and examined digital communication between sensor module and Arduino Uno with oscilloscope.

Indivudial Assignment

Board Design

For this week assignment, I desiced to use an ultrasonic sensor as input and for that, I needed to make a new pcb as a connector. To design and make schematic of the board, my groupmate, Antti, helped me a lot. After a quick research in former students pages, I almost understood what I should do. In the beginning, I tried to use the Elena's schematic as the reference, but Antti suggested me to make it from scratch. So, first of all, I made a list of components I might need for the board:

• ATtiny1614 (12 io pins). I chose ATtiny1614 for its larger mempory
• 1 x 1 uF capacitor (for ATtiny to work)
• 1 x 3 pin male header for UPDI
• 1 x 6 pin male header for FTDI
• 1 x 4 pin female header for sensor
• 1 x connector 02 x 03 odd_even
• 1 x Ultrasonic sensor HC-SR04
• 1 x blue LED
• 1 x resistor 1K OHM

Figure 1. List of components used for the new pcb

Then, I started to create schematic in KiCad with the experience I gained from Week 6 (Electronic Design) while I learned a couple of shortcuts used in KiCad from Antti Mäntyniemi.

Figure 2. Schematic of the new board in KiCad

For the reference to figure out how to connect the components, I used ATtinyX14 pinout map:

Figure 3. ATtinyX14 pinout

After clicking Run Pcbnew, I noticed theres is some error in assigning footprints, so checked it again and found that one symbol has not been assigned yet (Figure 4).

Figure 4. Error in assigning footprints

So, I assigned it from Footprint Libraries->fab, then, from Filtered Footprints and finally,Applied, Save Schematic & Continue as shown in Figure 5 and continued.

Figure 5. Assining the correct footprint from the selected library

Then, I clicked Update PCB from schematic and then, start wiring which was a bit tricky and needed to move or rotate the components.

Figure 6. Update PCB from schematic in KiCad

According to previous experiences and my groupmate advice, I modifed the clearance and track width values.

Figure 7. Editing board setup

Figure 8. Final PCB design in KiCad

Then, for milling the board with LPKF milling machine, I needed Gerber (.gbr) format of the Schematic file, so I opened Plot and chose only F.Cu and Edge.Cuts layers and plotted which generated .gbr files of both.

Figure 9. Converting .kicad-pcb to .gbr

Next, I started milling with LPKF milling machine Protomat S62 while contoling the machine with CircuitPro software (see more details in Week 6- Electronics Design).

Figure 10. LPKF milling machine chamber, table and milling bits

Milling the board with LPKF machine

Figure 11. Final milled board

Then, it was soldering time that I am not much interested into that!:D

Figure 12. Soldering the components to the milled board

Figure 13. Final soldered board

Ultrasonic Sensor

The HC-SR04 ultrasonic sensor uses sonar to determine distance to an object like bats do. It offers excellent non-contact range detection with high accuracy and stable readings in an easy-to-use package. It comes complete with ultrasonic transmitter and receiver modules.

Figure 13 shows HC-SR04 ultrasonic sensor pinout:

Figure 14. HC-SR04 ultrasonic sensor pinout [ref.]

VCC is the power supply for HC-SR04 Ultrasonic distance sensor which we connect the 5V pin on the board.

Trig (Trigger) pin is used to trigger the ultrasonic sound pulses.

Echopin produces a pulse when the reflected signal is received. The length of the pulse is proportional to the time it took for the transmitted signal to be detected.

GND should be connected to the ground of the board.

Testing the board

To test the board I made, I used the programmer board I made in Week 4 (Electronics Production).

Figure 15. Final soldered board

Then, I tried to attach the sensor to the connecotr and start programming but my groupmate, Antti, noticed that I have soldered a wrong pin female header because of the type of header I had selected in schematic which was odd-even (Figure 16)!:( Well, clearly, I am totally new to this world and those mistakes are part of the learning process (I hope so!:D).

Figure 16. The type of header in shcematic

So, I had to detach the wrong header and solder the correct one:

Figure 17. The modified board with the correct female header

When the board was ready, I started to conncet the sensor to the board considering the schematic of the board and the right pins for GND, VCC, TRIG and ECHO.

Figure 18. The connections between the programmer board, ATtiny1614 board and the ultrasonic sensor

For programming, I used Adrain's page and used his code as the sample while changing the pins for EchoPin to 9 and TriggerPin to 8.

Then, I uploaded it to Arduino IDE which was successful.

Figure 19. Uploading the code to Adruino

Next, I changed the connections to FTDI to test the program and see the results.

Figure 20. The connections for testing the programmed ATtiny1614 board and the ultrasonic sensor

Then, I openned the serial monitor and it automatically started to work and react to the distance by printing the input.

Figure 21. Testing the sensor's input in Arduino

Sounds it is working well!*__*

Testing ultrasonic_sensor with the programmed ATtiny1614 board

Reflection

During this week, I learned how we can program a board with Arduino to be connected to a device and receive the input parameters of that like an ultrasonic sensor which I tried for my assignment.