10/25/2025 - Research + schematics draft

Greetings, I am planning to make a custom devboard based on the ESP32-S3-Wroom1 with the size of a raspberry pi pico. I do intend however to have an IMU for future robotics/IOT projects, I think that would be a great addition to this board since the only devboard I am aware of that has that is the arduino nano IOT.

Since the WROOM1 has WIFI, BLE, Antenna etc built in that would really save a lot of costs and parts that has to fit into the sufficient yet constrained space that we have. I do also know for a fact after researching that ESP32 has its own devkit in that size, so I guess what sets my project apart is the IMU.

Below is the early draft of parts, after researching (tho not complete yet), I would need. All things still not yet final apart from the esp32 of course. We've got:

• ESP32-S3-WROOM1
• TPS63060 (buck-boost converter)
• BQ24072RGT (Li-Po battery charger)
• B2B-XH-ALFSN (Li-Po connector)
• USB-C receptacle
• Connector 01x20
• (CP2102N-Axx-xQFN20) USB-UART
• ASM330LHHXTR (IMU)

10/27/2025 - Drafting Schematic pt2

I found out that the ASM330LHHXTR was way too expensive of an IMU for a hobbyist. And so I looked for alternatives, lo and behold, the MPU-6050:

I struggled with the idea of, how would I classify this, boot-loading? What I mean to say is the question of how I was going to program my board. I found that the ESP32-devkit-C had two buttons: boot and reset.
What were they?
BOOT: pulls LOW to enter bootloader
RESET: pull LOW to reset chip
ok cool, but I know that I can just program an Arduino board by connecting it to the PC via USB?
Yes, and that's possible because of a pre-installed bootloader and USB-UART bridge that handles the reset.
So now I needed a USB-UART bridge (I already had one but I didn't know what it was for); I ended up switching to CH340C copying Arduino Nano's -cheap and works perfectly.
And then I noticed some pins on the CH340C datasheet that puzzled me: DTS & RTS
After reading, I found that they are control signals that would allow me to ditch the buttons. My IDE can toggle them to automatically reset the ESP32 and the bootloader. Also thanks to the ROM-bootloader I wouldn't have to install anything extra.

10/30/2025 - Routing PCB draft

The plan of making it in somewhat the size of a Raspberry Pi Pico is still on full steam. This is the first draft. Not every passive is there, but I think I've spent long enough for today drafting this:

Also, you may have noticed that the DHT11 sensor is not on the board. That is intentional as I am in a dilemma: to include or not to. It arose from its placement requirements, it can't be near ICs as they may tamper with the accuracy of the sensor. Plus the IMU as well have to be placed more meticulously and I still hadn't figured out where I would be positioning it. Below is the attached photo of the DHT which I had tried including a while ago:

11/1/2025 - Routing again

I've got to plan my layout once again. I opted to place the battery charger and the buck-boost converter on opposite sides almost mirrored on the USB and USB-UART bridge line:

But I do really need to make this neater, it doesn't look so appealing to me...

Future additions:

• NTC thermistor
• SMD temp sensors

there was a suggestion to me to tackle the sensitivity:
"place a connector and have a long NTC probe"

11/4/2025 - Finished routing

A rough look on how the board will look like. I don't quite like the large space at the bottom after the connector pins. Feels too bold. Looks too weird.

I guess I'm struggling with the layout, I don't know if that battery connector is gonna disrupt the IMU's accuracy. Need to verify with the community if that layout is alright. Will also ask the community for tips on improving the layout!

11/5/2025 - Re-routed PCB

Rather quick re-routing. I just pushed my components upward so now it's more compact.
This morning as I was scrolling through youtube I saw Phil's vid. That helped a lot with routing, but unfortunately I am still running into some problems with the DRC. Dominated by the error: thermal relief connection to zone incomplete, I can't quite find a solution to that yet.

I shall fix that error in the next journal

Edit: lol it was a quick fix, it didn't need another journal at all
So for the copper fills, it was just as easy as selecting solid instead of thermal reliefs. I also forgot to put a keep-out rule for the IMU which I did now :D

11/6/2025 - Increased pins + aesthetics

I increased the pins to 22 on each side after receiving advice from fellow hackClubbers. Not much trouble with routing there. I think I've gotten the hang of it.

Today, I finalized the PCB color to be black and added my personal touch to the board:

What took a long time was figuring out a way to make things more interesting with the board. I dug up Kai's message about the placement of which layer a vector image should be in. I found this

I wanted that shiny silver/gold for my elements. This was simply done by using the image converter from kicad. I created a footprint library for it and uploaded them on the layer F.Mask (B.Mask more accurately). I can't wait to manufacture this board!

11/7/2025 - BOM

Upon finding out that JLCPCB does not support ESP32-S3-WROOM1 for Economic PCBA, I headed to #blueprint to ask about alternatives. They replied:
1). Tbh if possible just hand solder it. Esp modules are not that hard to hand solder
2). the wroom 32e 8mb has economy pcba
3). ESP32-WROVER-B-N8R8
4). ESP32-WROVER-E-N8R8

Frankly I evaluated options with the intent to not have an extravagant schematic + pcb layout overhaul. I was fine with a few re-routes if the pins are not far too distinct. I then immersed myself into its respective datasheets and to my surprise I convinced myself that I am alright with hand-soldering the ESP32-S3-WROOM-1. What did? The dual-core XTensa LX7 of this module was too difficult to pass on. Perhaps the WROVER-E can get to 1/4th of its capability but I intend to use this devboard for future robotics projects and having a core that's ready for ML is a huge++.

11/10/2025 - IMU change + Cost optimization

I asked the community if there are any alternatives to MPU6050 as it just is too costly. ICM-42670-P was suggested to me since it is newer and cheaper! I rerouted the board, no major changes, took out a few passives only.

At that point the board was still costly due to the extended parts (about $30 worth). So I tried my figuring out resistors with basic libs either by making them 0603 footprint or rounding it up to the nearest basic resistor value. I did the calculations ofc to make it safe and reduced it further to $24 worth of extended parts. Now the PCBA costs $47

I am sourcing the ESP32, the ICM-42670-P and the 680k resistor (it was extended figured that it would save costs).