Hardware Overview

In order to bring some clarity about the hardware that we are working with, I thought I would type out some quick details about the hardware that our open-source Wireless Mesh module, the Swift01, is based on. The hardware design is very bare-bones as we have made every attempt to keep this design as inexpensive as possible.

Chipset

The main brain of our module is Atmel’s ATSAMR21E17A. This is a system on chip (SoC) that is essentially an AT86RF233 die packaged with a SAM D21 die. In our case, the SAM D21 is a 32-pin package with 128K of flash and 16K of RAM, but there is also a 48-pin package version and the memory size scales from 64K to 256K. The RF233 chipset handles the 2.4GHz communication and also has built-in hardware AES support.

The whole package that Atmel offers is very attractive to the DIY community with an open-source tool-chain and code libraries available for the MAC layer of the software stack.

Power

The chipset itself will accept power from 1.8-3.6V, but in order to qualify for FCC module pre-certification, the device needs to regulate its own power supply. To accomplish this, In Rev 2 of the board, we are adding a Micrel LDO voltage regulator (MIC5317) at 3.3V which is capable of accepting input voltages up to 5.5V. We will also add a cuttable-trace/jumper combination to bypass the regulator in case the user does not have access to a supply voltage higher than ~3.45V.

Memory

The Swift01 has an SOIC8 footprint for a SPI flash memory on the circuit board. This is to enable future features such as OTA programming and on-module scripting. Currently, the plan is to populate that footprint with an 8Mbit flash.

Serial Interface

With a serial bootloader already installed, the device can be updated and configured over a serial connection arranged to match the pinout of the Sparkfun FTDI Basic Breakout board.

Inputs and Outputs

The module has a number of external I/O pins accessible from castellated (PDF) holes on the board edge. 2 Analog inputs/outputs, 4 Digital inputs/outputs, and full access to one processor serial unit yielding a UART, SPI, or I2C connection (4 pins). All I/Os can be used as digital I/Os and 9 of the pins can use digital interrupts.

Antenna

The device is equipped with a 2.4GHz trace antenna design according to Texas Instruments’ AN043. This is a pretty good, omni-directional antenna, but also about as low-cost an antenna as you can get.

FCC Certification

One major goal of this project is to pre-certify the module with the FCC. This should open the door to using this module in a much broader range of applications and even allow it to be integrated into other products.

ECAD

The v1 board was designed on Upverter using the CERN Open Hardware License and the schematic and layout source files are accessible here:  https://upverter.com/dantheman2865/75c8af0c10cff21f/Swift01/

Conclusion

This is the design as of v1, but I would love to get the community’s feedback on this design and understand if there are any other features that would make sense for this design.

Thanks!

Dan Kurin
Founder, CEO of Swiftlet Technology