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Kris Winer designed this is a small 4-layer PCB for remote logging of absolute position and orientation:


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STM32L433-based board with CAM M8Q concurrent GNSS, EM7180 + MPU9250 + MS5637 for absolute orientation, and an ESP8285 for wifi connectivity.

The absolute orientation engine uses the MPU9250 accel/gyro/magnetometer IMU sensor plus the MS5637 barometer as slaves to an EM7180 motion co-processor that sends quaternions and drift-stabilized altitude to the host via I2C.

PeskyProducts has shared the board on OSH Park:



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STM32L4 Sensor Tile

From Kris Winer on


STM32L4 Sensor Tile

Small, connected device for smelling and hearing in any environment.

This is a 20 mm x 20 mm four-layer pcb tile full of interesting sensors (ICS43434 I2S Digital Microphone, MPU6500 acclerometer/gyro, BME280 pressure/temperature/humidity, and CCS811 air quality) with a Rigado BMD-350 UART BLE bridge for sending data to a smart phone all managed by a STM32L432 host MCU.

The STM32L432 is programmed using the Arduino IDE via the USB connector and serial data can be displayed on the serial monitor to verify performance and proper function, etc. But it is intended to be powered by a small 150 mAH LiPo battery for wireless sensing applications. The STM32L4 is a very low power MCU and with proper sensor and radio management it is possible to get the average power usage down to the ~100uA level, meaning a 150 mAH LiPo battery can run the device for two months on a charge.

A library for it is available on GitHub:


A collection of sketches to run the STM32L432-based (20 mm x 20 mm) sensor tile with an MPU6500 accel/gyro, ICS43434 I2S digital microphone, BME280 temperature/pressure/humidity sensor, and CCS811 air quality sensor. The sensor tile has an on-board MAX1555 LiPo battery charger, an on/off switch, and a Rigado BMD-350 nRF52 BLE module.




STM32L4 Sensor Tile

Hackaday Prize Entry: Sub Gigahertz RF

For his Hackaday Prize entry, [Adam] is working on an open source, extensible 915 and 433 MHz radio designed for robotics, drones, weather balloons, and all the other fun projects that sub-Gigaherts radio enables.

The design of this radio module is based around the ADF7023 RF transceiver, a very capable and very cheap chip that transmits in the usual ISM bands. The rest of the circuit is an STM32 ARM Cortex M0+, with USB, UART, and SPI connectivity, with support for a battery for those mobile projects.

via Hackaday Prize Entry: Sub Gigahertz RF — Hackaday

Hackaday Prize Entry: Sub Gigahertz RF

Mesh networking for sensor grids

Mesh networking board by Daniel on


Low-power mesh networking for small sensor grids

Tiny MQTT-interoperable broadcast mesh networking with simple radios

This project is a low-resource mesh networking stack and mote with battery-powered routers based on state synchronization. The target is for the stack to use less than 2kb SRAM. Nodes use low power listening and an adaptive gossip protocol to synchronize key/values pairs with each other without relying on explicit routing or per-node addressing.


For example, a light might transmit (/lamp, {“state”:”on”}) to the mesh. Write (/lamp, {“state”:”off”}) to the mesh, and the lamp application will notice. The powerful but simple state synchronization primitive allows you to update the state of the mesh to update the world, and update the state of the world to express the same on the mesh. Trivially bridged to a private MQTT server and managed with off-the-shelf MQTT applications.

The design files and source code are available on Bitbucket:


Mesh networking for sensor grids

Castellated Edges

Castellations are small plated edges, typically used for making circuit boards into small PCB modules. These are often seen on wireless modules, such as the ESP8266-12E.

While we don’t offer full support for castellations, they can be fabricated if you don’t mind a few minutes of rework and verification of the PCBs.

Design Considerations

It’s helpful to include a fallback hole near the edge. The ESP8266-12E boards, are a great example here. The extra via allows easy connecting of wires for rework, and makes it easy to salvage a module if the fabricated PCB doesn’t turn out perfectly.

ESP2866-12E, available at

Indicating in the design file

Castellations are simple to call out in most design tools. Simply include a via on the PCB, so the board outline goes through it.

However, due to our panelization process, the castellated vias must be indicated with round pads for copper and stop mask. The pads must also not extend more than 40 mil from the board edge. Square pads or pads that extend far beyond the edge will be trimmed, and the via will not be plated.

It’s also helpful to use a 10 mil wide line for the board outline. With our milling tolerance of 5 mil, this provides a good visual indicator of where the physical board edge might be. The fabricated edge can be anywhere within that line. This is very helpful for fine-pitch castellations with smaller holes.

Callout as seen in a design tool
Callout as seen in a design tool

Rectangular castellations can be made by using vias with round pads as noted above, and adding overlapping rectangular SMD pads. Since these pads are inside the board outline, they will not be trimmed, and will provide additional area for soldering (see below for example).

Cleaning up the final boards

We make a best-effort to minimize support tabs on castellated edges, but it sometimes happens. In these cases, you’ll need to file the tab off of your edge.

Additionally, the via plating may not be fully removed during the milling process. In some cases it’s smashed next to the edge, where it can cause unwanted connectivity between vias. In others, it’s smashed inside the via, where it will prevent good solder flow. A fine point file or hobby knife will help remove excess plating.

An unreworked castellated PCB, with visible plating stubs
An unreworked castellated PCB, with visible plating stubs
Another version, with tabs on castellated edge and modifications for rectangular pads
Another version, with tabs on castellated edge and modifications for rectangular pads
Castellated Edges

SIS-2 Universal Remote Receiver

Jeremy Cook writes on the Tindie blog about this IR receiver board by Atomsofttech:


SIS-2 Universal Remote Receiver

When you think of a “universal remote,” you generally picture an infrared (IR) emitter that can be setup to control your TV, AV receiver, and any other number of devices that work using IR signals. On the other hand, what’s to keep someone from doing the opposite, and having a universal receiver that can be programmed to accept codes from a remote that you just have lying around?

Watch the receiver board in action:

SIS-2 Universal Remote Receiver


Patrick Van Oosterwijck created an audio BLE beacon that can be activated by the vision impaired to find exact locations of doorways, bus stops, crosswalks, and more:



The idea is that a blind person uses a navigation app, and can query to see “what is around”. In the list of beacons that are around, they can tap the one they want to know the location of and it will start to produce an audible signal for a short time.

The BLE module is configured as an iBeacon and allows connections. It has a battery service and an “Immediate Alert” (AKA “Find me”) service.

Patrick used the following to build the prototype:

  • A 550 mAh 3.2 V LiFePO4 cell
  • A #LiFePO4wered/Solar1 prototype to charge the battery
  • A 5.5V, 0.6W monocrystalline solar cell
  • A Silicon Labs (formerly BlueGiga) BLE113 module
  • A beeper that works very badly (better solution needed)
  • And a IP65 enclosure

xorbit has shared the booster for loud piezo beeper on OSH Park:



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