Starting the PCB!!!

First I created a new folder in Autodesk Fusion 360 project called “landing station” because now I will start with the landing station!!!!

Yesterday in class we had a substitution lesson and I had 90 minutes to think of a concept for my landing station, and my planning looked like this:


Basically:

1. I thought of making a funnel-like structure on the top that is 10mm wide so that if the drone has an error of max 10mm it would center itself
2. It’s separated into 2 parts: the platform with the walls, and the funnel part — I’ll do it in two parts so it can be printed better and without problems
3. I decided to make a plate exactly under the position of the camera so the drone can land perfectly
4. There will be LEDs or a small display that shows the battery percentage and whether it is charging, and the landing station will be powered by USB-C and the power goes through pogo pins into the drone
5. The whole thing will be about 50mm tall so the drone can still recognize the AprilTag in the last centimeters of landing
6. Everything will be mountable without screws so parts like the AprilTag holder can be moved forward/backward for adjustment

After that (now), I first wanted to create a new file called “platform”, but when I tried I got a message that I reached the document limit, so I was cooked T-T.

So I submitted the form for pro for students, but it takes up to 24h. SOOO I decided to make the PCB of the drone instead (scared, never did a PCB before!!!).

So I started KiCad and created a new project.
Then I had to check how I could add a Raspberry Pi and the flight controller so I can make my circuits.

For that I first opened the MAVLink connection video again to check which pins I needed. I saw that I needed TX2, RX2, and GND → so 3 wires.

Then I remembered JST-GH connectors, which are like safer and better male/female connectors. So I decided to use them. The Raspberry Pi would then connect like this:

RX2 → TX2
TX2 → RX2
GND → GND

At first I didn’t really understand what these pins do, so I started researching:

TX (Transmit): sends data out
RX (Receive): receives data

So basically they allow communication, and the drone can receive commands from the Pi.

After that I wanted to add a 2x20 pin header so the Raspberry Pi can connect later. I didn’t know KiCad, but I found out that you just press “S” and search the component, and then I found Conn_02x20_Odd_Even.

Then I added JST-GH 3-pin connectors and after checking I found Conn_01x03.

But the KiCad workflow confused me at first!!! But then I understood that you first design the logic in the schematic and then define the physical PCB layout.

So I started drawing the Raspberry Pi and the flight controller:

Then I continued adding the servo motor JST-GH and the 4 sensors, but I was so tired (0:20am) that I went to sleep:

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Next day: continuing PCB
(Btw my Fusion 360 student pack got approved!!!)

I started adding the 4 connectors (JST) for the ToF sensors. They have 4 pins:

After that I started wiring Raspberry Pi ↔ Flight Controller connections.
I didn’t know how to connect them, so I searched and found:

• W = create wire
• L = create label

So I checked which pins are TX2/RX2/GND on the controller:

Then I added labels:

After wiring the FC and Raspberry Pi, I continued with the 4 sensors.
But then I realized I should combine them properly, so I researched and found that I should use I2C.

I2C allows multiple sensors to connect to one controller using only 2 wires. It avoids conflicts that would happen if each sensor had a separate connection.

At first I wasn’t sure how it worked, but then I understood it better:

Instead of directly asking each sensor, the controller communicates through a shared bus.

But then I still wasn’t sure, so I chose the TCA9548A, because:

• very common
• 8 channels (very good)
• well documented

So I started integrating it:

After reading the datasheet I understood:

• SCL/SDA → Raspberry Pi I2C pins
• GND → GND
• VCC → 3.3V
• pull-up resistor (10kΩ) for safety

Then I connected A0/A1/A2 to GND to set the I2C address (0x70).

Then SCL/SDA of the sensors connect to channels 0–7.

But while doing that I noticed something important: the ToF sensors actually have 6 pins, not 4:

Pins:

• VCC → 3.3V
• GND → GND
• SDA → data
• SCL → clock
• XSHUT → enable/disable sensor
• GPIO → not used

So I updated everything and changed the connectors to 5–6 pin layouts.

Quick update:

Then I connected:

• VCC + GND
• XSHUT → 3.3V
• SDA/SCL → I2C bus

After that I moved on to the servo motor.
I wasn’t sure if I could power it directly from the Pi or not, so I searched and found out:

You should use an external 5V supply for better stability.

So I decided I need to design the full power system of the drone first. That will be harder, but I will need it anyway.

But since it was already late and I have a physics test tomorrow, I stopped here and will continue tomorrow with the power system.

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Overall I’m really happy with the progress. I learned a LOT about KiCad, PCBs, I2C, and electronics in general. Tomorrow will be power supply day!!