Sam

I'm a remote contractor working for international clients. The main client I worked for was Wagz, a US company making smart dog collars featuring GPS tracking and containment technology that communicate metrics on the pet's health to the cloud.

Tasks and achievements include implementing:

• Initial driver for the u-blox SARA-R5 LTE cellular modem with integrated GNSS functionality.
• New Git workflow for firmware release management, which was ultimately adopted.
• BLE characteristic for reporting pet walk information.
• Power-saving measures, including cellular eDRX and CPU light sleep.
• New state machine for controlling when cellular transmissions occurred based on signal strength.

Technologies used: C, ESP32, FreeRTOS, AWS IoT SDK, WiFi/BLE/LTE/GNSS, PlatformIO and Ceedling unit testing, GitHub Actions.

Project size: 60k lines of original code in a single repository shared by multiple devices.

Switchee is a UK start-up company that invented a smart thermostat for the social housing market, providing data-driven property insights to landlords and energy savings to tenants.

I was in the founding team developing the new generation of thermostat, Econa, consisting of: (1) a battery-powered e-paper display unit; and (2) a mains-powered hub that controlled the heating system and sent sensor information from the display to AWS via lwIP and a cellular connection.

Tasks and achievements include implementing:

• GUI for the display unit using the LVGL graphics library and simulator.
• Screens for new features such as creating heating schedules.
• Optimised rewrite of the e-paper graphics driver.
• Data transfer mechanism for transferring firmware images over the bespoke wireless link (between hub and display) while utilising low-power modes. * Intelligent download manager for resuming firmware downloads when they fail due to packet collisions between different "piconets" (networks of hubs and displays in neighbouring properties).
• Battery-usage statistics collection on the display, with subsequent transfer to the hub.
• Custom bootloader with firmware upgrade capability, shared by both the hub and display.
• Integration of AWS IoT SDK and mbedTLS library into the hub code base for secure MQTT cloud connectivity.

Technologies used: C, STM32 F4 and L4 series, FreeRTOS, e-paper, LVGL, mbedTLS, lwIP, AWS IoT SDK, OTA, LTE, sub-GHz radio, Python.

Project size: 50k lines of original code between two main repositories, one each for the hub and the display unit.

Various projects for the Australian government incorporating: hardware design, schematic capture and PCB layout, firmware, embedded Linux systems, and reverse engineering.

• Electronic circuit design: Eight-layer PCBs, blind and buried vias, high-density interconnect (HDI), impedance matching.
• Schematic capture and PCB layout: Mentor Graphics Xpedition and Altium EDA / CAD tools.
• PCB manufacture: Ordering parts and blank PCBs, SMT assembly with pick-and-place machine, testing, solder rework.
• Embedded Linux development: Gumstix computer-on-module, Yocto Project, BitBake, kernel configuration, driver modification, application software.
  Reverse engineering of embedded Linux systems.