Devlog 1: The 43-Minute Charging Core

Project Context & Architecture

I’m designing a custom handheld navigation device from scratch. The goal is a custom carrier board in KiCad that ties together high-performance computing, location tracking, and power management. Here’s the hardware stack:

• The Brain: Raspberry Pi Compute Module 4 (CM4) — Runs the core OS, custom parsing utilities, and handles all the high-level computing.
• Location Tracking: u-blox NEO-M9N GNSS/GPS Module — Connected to an active external antenna for live coordinates literally anywhere.
• Power Management: BQ25895RTWR (QFN-24) — A highly efficient switch-mode 3A buck charger handling autonomous LiPo charging, direct power-path management, and a deep-sleep “Ship Mode” hibernation circuit to prevent battery drain.
• Power Input & Battery: USB-C Interface & 1S LiPo (via JST-PH) — Hardwired strictly as a one-way power sink (charging input only because I have zero motives to actually use the port for anything else).

The Update

PS: My incompetent brain used plain text boxes for my schematic labels instead of just pressing the L key to make actual net flags.

So, here’s what I got done in exactly 43 minutes: a charging circuit. That’s it. That’s literally all I did. Right now, there is absolutely nothing connecting over to the CM4 compute engine yet. I’m an absolute beginner at physical PCB layout, but I am a certified pro at reading datasheets. If you think about it, it’s the biggest engineering bottleneck of the century. Either way, I need to get this entire hardware project finished by tomorrow to actually get this PCB sent over to JLCPCB, get leads on parts, get it shipped ASAP, and take measurements for the enclosure. (That is if I get actual funding..) I’m currently sitting at a solid 5% completion. This is going to be an absolute sprint. (Not like my teachers once asked me to write a drama script last minute that was like 50% of my grade and I managed to pull off a 30-page script in one night… but yeah.) I’ll see you in a bit when I’ve actually got a few more sheets knocked out.