Hardware

Each layer is printed on a 53 x 53 mm PCB and it is populated by 4 through hole 14-pins connection ports one for each side. Each port forwards signals to the top and to the bottom making it possible to create a stack of several layers.

The MCU layer

MCU layer

The basic layer containing the MSP430 MCU, eeprom, EUI-48, and RTC.

The MCU layer contains the MSP430F5418A micro-controller unit (MCU), the 512K serial eeprom, the 48-bit Extended Unique Identifier (EUI-48), and the Real-Time clock calendar.

The micro-controller unit has an optimized architecture and exhibits a large set of low-power inactive modes (ranging from ≈0.1µW to ≈73µW) conceived to achieve extended battery life in portable measurement applications and to enable the implementation of autonomous WSNs harvesting supply power from the environment. Nevertheless, the MCU is a powerful 16-bit RISC CPU running at up to 25MHz with a built-in digitally controlled oscillator (DCO) which allows wake-up from low-power to active modes in less than 5 μs.

[Schematic][KiCad/Gerber][Functional Diagram] – V1.1.0

 

 

 

The Radio and Sense layer

Radio and Sense layer

The radio and sense layer with the Texas Instruments CC2520 RF transceiver, temperature, luminosity, and pressure sensors.

The radio layer hosts a Texas Instruments CC2520 RF transceiver, a second-generation ZigBee/IEEE 802.15.4 RF transceiver working in the 2.4 GHz band. CC2520 RF provides several integrated features, including: hardware support for frame handling, data buffering, burst transmissions, data encryption, data authentication, clear channel assessment, link quality indication, frame filtering, standard RX mode, and low-current RX mode. All these built-in features significantly reduce the MCU computational load and power consumption.

Temperature, luminosity, and pressure sensors are pre-installed on this layer to facilitate simple applications development.

[Schematic][KiCad/Gerber][Functional Diagram] – V1.1.0

 

The Programmer layer

programmer

The Programmer/Debugger layer

The programmer and debugger layer is a low-cost solution to fully programs and debug the VirtualSense node. In fact, it allows MSP430 programming, througth the built-in USB  port (in BSL mode), and RS323 communication without need to buy a dedicated programmer hardware or software. In the same time, it allows JTAG programming and debugging, through a dedicated port, using a standard Texas Instruments MSP-FET430UIF programmer.

Finally, the programmer layer acts also as a power supply converting the USB 5V to a 3.3V to powering VirtualSense.

[Schematic][KiCad/Gerber][Functional Diagram– V1.1.0

 

 

 

The Power Supply layer

battery

The Battery Power Supply layer

The Power Supply layer hosts 2 AAA batteries needed to powering the VirtualSense mote. It is designed to easily test and deploy a small in-lab network. It is also equipped with an on-off  switch and with a protection fuse.

[Schematic][KiCad/Gerber][Functional Diagram– V1.1.0

 

 

 

 

 

 

 

 

The Ultrasonic Wake-up and

Distance measurement layer

audio_trigger2

The Ultrasonic Wake-up Trigger and Distance Measurement

The Ultrasonic Wake-up and Distance measurement layer gives to VirtualSense the capability of triggering the wake-up of a node over the air. This layer supports a simple out-of-band addressing scheme to enable the selective wake-up of a target node. In addition, it makes it possible to exploit the propagation speed of ultrasonic signals to perform distance measurements.

[Schematic][KiCad/Gerber][Functional Diagram] – V1.1.0