Device Provisioning Is an Identity Problem Disguised as Wi-Fi Setup
Getting credentials onto a device is easy; binding the right device to the right backend identity is the security boundary.
TOPIC
Embedded & Firmware
Lessons, explainers, experiments, and implementation notes.
Signed Dual-Slot OTA Needed an Acceptance State, Not Just a Boot Flag
A new image should become permanent only after the device proves it can boot, verify, connect and report healthy.
RTP Playout Got Better When I Stopped Letting Packet Arrival Drive the Speaker
Network arrival time is not an audio clock. A stable playout schedule needs its own timing and buffer policy.
I2S Audio Made Timing Bugs Audible
Digital audio bugs are often scheduling and buffer bugs that happen to come out of a speaker.
Signed Firmware Changed OTA from File Delivery into a Trust Decision
A device should decide whether firmware is authorized, not merely whether the download completed successfully.
The ESP32-S3 Voice Pipeline Was Really Several Clocks Sharing One Device
Microphone sampling, RTP packetization, network arrival and speaker playout each have their own timing domain.
What Happens if Power Fails While Writing Flash?
It is easy to think of saving data as one indivisible event: write it and it is done. In reality, power can disappear in the middle of a write. The next boot then has to distinguish complete, incomplete, and usable state.
E-Paper UI Design Forced Me to Treat Refreshes as a Resource
A slow monochrome display changes interaction design: information hierarchy matters more than animation.
A Watchdog Should Observe Progress, Not Just a Timer
A regularly fed watchdog does not prove that important work is progressing. A dedicated task can keep feeding the timer while an audio or network task is stuck, making the real failure invisible to the watchdog.
AEC Only Worked Once the Reference Signal Was Actually the Far-End Audio
An echo canceller cannot remove what its reference channel does not represent.
Watchdogs Are Useful Only After the Firmware Has a Recovery Story
Resetting a stuck device is not the same as fixing it; watchdog design needs crash evidence and bounded recovery behavior.
My ESP32 Wi-Fi Lab Started with Reconnects, Not Features
An embedded network client is only useful if it survives AP loss, DHCP renewal and reconnect loops without wedging the application.
AEC Debugging Started with Channel Mapping, Not DSP Tuning
Before tuning echo cancellation I verified that the algorithm was receiving the microphone and far-end reference channels I thought it was.
OTA Updates Became a Reliability Problem Before They Became a Delivery Problem
Downloading new firmware is easy; proving the device can recover from a bad update is the real OTA design work.
A SIP Endpoint on an Embedded Device Changed My Definition of 'Small'
Once SIP, RTP, codecs, Wi-Fi and a UI share one MCU, memory and timing decisions stop being implementation details.