Hardware v0

If you are interested in aquiring a pre-built devboard, please contact @abenstirling on the Discord server. Otherwise the hardware exports are found here, and the BOM is found here

The goal for the hardware is to have a fully integrated:

Microcontroller
UWB module
Lights for visual feedback
Battery management system (for low power consumption)

Devboard

We currently have a devboard that is being used for development. The devboard is a custom PCB that has the following components:

ESP32-C3-MINI-1
DWM3000
2x RGB LED
USB-C for power and programming

Devboard

For the input, we need typical USB-C pins. I didn’t connect any pin other than the required ones for it to function with data and power. DP and DN are for data, VBUS is for +5V, and GND is for GND. I also have an output for us to check for shorts and worst-case to power the board.

Devboard

For the ESP32, this was gathered mostly from the datasheet. Shoutout to the ESP32-C3-MINI-1 datasheet! Most importantly, we have Boot and Reset buttons. We have two bypass caps with +3.3V. A big thing to realize (that is actually non-trivial) is that the pins on the footprint/symbol are not the same as the GPIO pins on the ESP32. This is because the ESP32 has a different pinout than the footprint. Just remember!

We wire up the following:

DWM3000_IRQ - IO1
DWM3000_SPICLK - IO4
DWM3000_SPIMISO - IO5
DWM3000_MOSI - IO6
DWM3000_SPICS - IO7

DP and DN are always on IO19 and IO18 respectively. The IO10 is a testpoint, not sure why.

Hardware

Again, this is retrieved from the datasheet. LED/resistors are used to debug when figuring out SPI comms.

Hardware The LM1117MP-3.3 just needs 10u bypass caps on either side. I also put LED/resistors for debugging power.

Hardware The SK6812 just need 1u bypass caps, they are “daisychained” so are controlled by NEOPIXEL pin, GPIO3.

Hardware They layout is quite supreme, as the ESP32 is just nicely perpendicular to the DWM3000. The board is 50mm X 50mm, with 5mm£ radius corners, and 3mm mounting holes on a 40mm grid. The only thing to note is that I did not fill copper on either layer under the antennas of the wireless chips, likely to help with proper signal.

Hardware The devboard is housed in a 3D printed case. The case is designed to be small and portable. The case has a hole for the USB-C port, and a hole for the the switch to switch power. A true mechanical wonder.

Battery Tester

Battery Tester For testing our battery management system, we have a battery connector that can be used to connect a battery to the devboard. The requirements are as follows:

USB-C for power and programming
Battery connector
Voltage regulator
Battery management system

Let’s take a look at the battery tester in more detail:

Battery Tester

For input, we have a USB-C. I didn’t connect any pin other than the required ones for it to function as a power source. CC1 and CC2 always need 5k1 pulldown resistors, and SHELL_GND always needs a 100k pulldown. We used VBUS for +5V and GND for GND.

Battery Tester

We have the meat of the battery board here. We have a MCP73831-5-OT which is an IC that is meant for this type of application. Mew463’s ESP32 Caliper was a big help to apply some of the concepts from the datasheet. We added a switch so the user can turn off the battery power at any point.

Battery Tester For the output, I decided to have a LP5907MFX-3.3_NOPB regulator right next to the battery because it is meant for the battery. The two ouput pins are meant to be connected to the 3V3 and GND pins on the opentag devmodule.

Battery Tester For routing, I tried to use as many power puddles as possible. I also tried to keep the traces as short as possible. I also tried to keep the traces as wide as possible. Nothing too special here.

Hardware Hardware v1