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There is an issue when trying to program a SAMD21 like in the Arduino Zero using OpenOCD with a ST-Link v2 which gives errors like this: ** Programming Started ** auto erase enabled Info : SAMD MCU: SAMD21E18A (256KB Flash, 32KB RAM) Error: Failed to erase row containing 00000000 Error: SAMD: failed to erase sector 0 Error: failed erasing sectors 0 to 0 The issue is that NVMCTRL_CTRLA is a half-word register and the ST-Link v2 emulates the half word write using two single byte writes.


In follow up to my build, I’ve always wanted to design PCB and try my hand at SMD soldering. I normally use veroboard on a 0.1” pitch but the time to cut and solder wires makes for a slow build. Here’s the result: It has: An AT91SAMD21E18 (256 KiB flash, 32 pins, 0.8 mm pitch) USB, regulator, Cortex SWD debug header, LED, and pullups on I2C Footprint for a RFM69CW radio Adafruit Feather form factor Two layer PCB with 0603 passives The soldering turned out well.


It gets warm and humid here in the summer and feels too dry in the winter. To measure this I built up two MySensors Sensebender Micro boards and designed a 3D printed a case to go with them: The holes in the case are to save on print time and let the air flow. The battery is far oversized and probably self discharges faster than the board draws current. I ended up using a Raspberry Pi Zero with a RFM69HW as the gateway.


As part of adding MySensors based sensors around the house, I want to make an integrated version of the Sensebender Micro upgraded with a SAMD21 and a RFM69HCW radio. I’ve never had much success with making PCBs at home, so I thought I’d give it another try and record the experiments. Try 1: HP M252dw, laminator @ 10 mm, 4 times through, Migros-brand T-Shirt transfer paper. Some transfer but lots left behind.


The short story is that this blog is now available on IPFS at and This is done by generating the blog a second time with ipfs/ as the basepath, changing to relative links, and then adding and updating the name as part of the buildbot script. Hugo has relative and canonical link support but it seems inconsistent, and it’s hard to resist a sed script… I quite like how you can map ownership across DNS and IPFS using a TXT record.



C++ in 2017

Seeing how C++17 compares to Go


A fast indoor mousebot


A rover tracking camera


A balancing robot written in Go and running on ARM Linux.


Ideas for future projects.


Some things I’ve hacked on.

PL/0 implementation

A toy compiler for the PL/0 educational language.


Markdown templates for project plans, etc.


The Never complete; often never started autopilot.


ser2neo makes it easier to drive a NeoPixel ring