Dev Notes

GPS RTC Backup Power: Why I Replaced the MS621FE Coin Cell with a CPH3225A Supercapacitor

Sep 06, 2026

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11 min read

GPS RTC Backup Power: Why I Replaced the MS621FE Coin Cell with a CPH3225A Supercapacitor

A design decision breakdown for GPS module RTC backup power — comparing the MS621FE rechargeable coin cell against the CPH3225A supercapacitor on the MAX-M10S, covering backup duration math, India sourcing, and PCB footprint tradeoffs.

#KiCad 8.0 #GPS #PCB #Power Electronics +2

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The Raspberry Pi Power Trap: GPIO Back-Powering, SD Card Death

Aug 23, 2026

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14 min read

The Raspberry Pi Power Trap: GPIO Back-Powering, SD Card Death

A dev-notes breakdown of why Raspberry Pi companion computers keep dying in robotics builds — GPIO back-powering, SD card corruption on power loss, and power-bank brownouts.

#Raspberry Pi #Power Electronics #PCB #Robotics +2

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Complementary vs. Mahony vs. EKF: Choosing the Right Attitude Estimator for Your Drone

Aug 09, 2026

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13 min read

Complementary vs. Mahony vs. EKF: Choosing the Right Attitude Estimator for Your Drone

A practical breakdown of the three dominant drone attitude estimators — Complementary Filter, Mahony Filter, and EKF — comparing computational cost, accuracy, and the hardware each one actually needs.

#Drone #Embedded Systems #Sensor Fusion #EKF +3

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I Got My DGCA RPAS Pilot Certificate. Here's What the Exam Doesn't Teach You.

Jul 24, 2026

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12 min read

I Got My DGCA RPAS Pilot Certificate. Here's What the Exam Doesn't Teach You.

An embedded systems engineer's honest take on India's DGCA RPAS Remote Pilot Certificate — what the exam tests well, what it completely ignores about drone engineering, and where Digital Sky creates real friction for custom firmware builders.

#DGCA #Drone #Robotics #India +2

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Designing a 4S Smart BMS with the BQ76920: Every Trap I Hit and How I Fixed It

Jul 14, 2026

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12 min read

Designing a 4S Smart BMS with the BQ76920: Every Trap I Hit and How I Fixed It

A KiCad design diary for a 4S Smart BMS using the TI BQ76920 AFE and TPS5430 buck converter — covering cell mapping, resistor math errors, and schematic traps before fabrication.

#KiCad 8.0 #BMS #BQ76920 #PCB +2

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