Part of my project to write new firmware for the Aqara E1 Zigbee light switches involved implementing the Zigbee Cluster Library OTA Update function. It didn’t go particularly smoothly, with two main obstacles. Firstly:

Sanity check - Blinky For an initial sanity check, I modified the NXP SDK’s blinky example for the 4 LEDs of the Aqara QBKG41LM (DIO lines identified here) to make sure that it would accept and run new firmware.

Any new firmware needs to know the GPIOs After confirming that the chip had write access in ISP mode, the next step was to determine the appropriate inputs and outputs.

Aqara are one of the few manufacturers producing affordable, well built, Zigbee “compatible” light switches that are both available in my part of the world, and suitable for local electrical installations. Aqara are a brand of Xiaomi-backed Lumi United Tech.

Smart homes save energy right? Occupancy sensors turn off lights in vacant rooms, scenes and timers activate only the devices that are needed, only when they’re needed, and energy use feedback adjusts our behavior.

A comprehensive list of major Zigbee IC vendors and module makers, including a matrix of which module maker use which vendor's ICs.

After measuring the standby power consumption of various Zigbee and Z-Wave devices, I became curious about what efficiency regulations governed them. The EU has typically been at the forefront of energy use regulations, famously introducing the idea of a common charger back in 2009 before later mandating it, and issuing ecodesign requirements for transformers as early as 2009 (EC No 278/2009). Infact their first energy labelling directives were issued way back in in 1979.

How to configure an ATMega328p to consume lest than 1uA, while still retaining the ability to wake the processor up periodically via timer (or external interrupt).

Discussion of the design and implementations problems encountered during the design/construction of my in-wall Bluetooth audio player, with environmental sensors, proximity wake-up, metadata display, and cat animations.

Installation, power, and speaker connections for the custom made in-wall Bluetooth audio player. The wall plate connects to the speaker connections and power control electronics via a single RJ45 cable.

Firmware design for the Bluetooth audio player project. The basic architecture uses events to trigger external interrupts. Handlers post the event details into a queue and a simple control loop polls the queue and dispatches events to various handlers.

Mechanical design for the in-wall Bluetooth audio player project. The most difficult aspects of the design are mechanical. Fitting the module into a standard electrical junction box without visible fasteners, while allowing for it to be easily removed and look good is quite a challenge.

Circuit and PCB design for the Bluetooth audio player project. The circuit design is not complicated. The main sections are MCU with 8MHz crystal and supporting caps, ...

My latest project is a cat-themed Bluetooth audio player to be permanently installed in my bathroom. The unit will be housed in a standard electrical junction box on the bathroom wall..

STM32 microcontroller cheat sheet by product line, feature, model number. Includes product code descriptions and timer/peripheral information.

This is part 4 of a 4-part series on building a toaster reflow oven: Oven hardware Controller hardware Manufacturing Controller software Continuing on from the prior posts on the controller hardware and manufacturing, the device needs software.

This is part 3 of a 4-part series on building a toaster reflow oven: Oven hardware Controller hardware Manufacturing Controller software So far we’ve looked at the hardware design, but aside from modifying the oven in part 1, nothing has been built yet.

This is part 2 of a 4-part series on building a toaster reflow oven: Oven hardware Controller hardware Manufacturing Controller software In part 1 we discussed the selection and modification of the oven itself. It’s now time to work on the external controller.