Oscilloscope Watch: The Time Of Your Engineering Life

Sam Davis

Power Electronics

Described as "The nerdiest thing you can put on your wrist.” The Oscilloscope Watch has the features of a modern watch (time, calendar, alarm, etc...) along with those of an oscilloscope, waveform generator, logic analyzer, protocol sniffer, and frequency counter. It was developed by Gabriel Anzziani, the founder and CEO of Gabotronics, a company that’s pushing the state-of-the-art for smaller and less expensive test equipment.


Figure. 1.	*Hand-held Xprotolab oscilloscope*

One of Gabotronics first products was the hand-held Xprotolab oscilloscope (Fig. 1) that served as a “template” for the design of the Oscilloscope Watch. The Watch is now a fully funded Kickstarter project whose first prototype is shown in Fig. 2. The watch is scheduled for shipping in 2014 for $150. The Xprotolab oscilloscope now sells for $98.
With access to the hardware design, users can write their own applications. The brain of the device is a powerful 8-bit XMEGA microcontroller, easy to program in C or assembly.


Figure. 2.	Prototype Oscilloscope Watch

Special attention has been given to extend the battery life of the device. When the Oscilloscope is not used, the analog section is turned off, so the estimated battery life will be over 30 days on each charge. When using the oscilloscope, the battery will last about 12 hours. These are initial estimates, and could be different if the battery capacity is changed to reduce the size of the watch. Fig. 3 shows the different operational modes.


Figure. 3.	*Oscilloscope Watch modes and functions*

The enclosure will be made out of plastic. Although the current prototype looks kind of big, it is not much bigger than a regular sports watch, but reduction of the size will be one of the goals of the project.

Probes are one of the challenging aspects of the design. The oscilloscope can't be truly wearable/portable if not accompanied by the probes. There are a few solutions for this problem:

Carry small probes in a keychain.
Make a wristband made out of the probe cables.
Use the probes as the watch straps.

The keychain is the most feasible option, maybe a small case, or perhaps a retractable cable, similar to those used with tiny USB mouses. Options 2 and 3 could also be considered if backers are interested.

A special BNC adapter will also be designed that will plug in the 9 pin header, this will allow to use standard probes.

The original Xprotolab uses an OLED display, which has nice features like high contrast, and fast refresh rates. But if battery life is critical, then OLED is not the best choice.

The Oscilloscope Watch will use a 1.28 in. e-paper display which combines fast refresh rate and great contrast, with a very low power consumption.

Features

Mixed Signal Oscilloscope: Simultaneous sampling of analog and digital signals.
Advanced Trigger: Normal / Single / Auto, with rising or falling edge and adjustable trigger level.
Meter Mode: Average, Peak to peak and Frequency readout.
XY Mode (Plot Lissajous patterns or see the phase difference between two waveforms).
Spectrum Analyzer with different windowing options and selectable vertical vertical log.
Horizontal and Vertical Cursors with automatic waveform measurements.
Arbitrary Waveform Generator with Sweep on all parameters.
Display options: Persistence, Different grid options, and more.
Curve tracer function

General Specifications

ATxmega256A3U 256 KB Flash, 16 KB SRAM, 4 KB EEPROM
Sharp Memory LCD display 1.28 in., 128 × 128 pixels
Approximate watch size: 2 × 1.6 × 0.6 in.
Li-Ion Battery 400 mAh, rechargeable via the micro USB connector
Internal PDI interface
8 tactile switches
USB connectivity: PC application available, Android App available.

Logic Analyzer Specifications

8 Digital Inputs, 3.3 V / 5 V tolerant
Maximum sampling rate: 16 MSPS
Frequency counter: 16 Mhz
Buffer size: 4096 bytes

Protocol Sniffer Specifications

UART: 5,6,7,8 data bit formats, 2560 byte buffer.
SPI: 439 kHz max clock, All combinations of CPOL and CPHA, 2560 byte buffer.
I²C: 400 kHz max clock, 2048 byte buffer.

Oscilloscope Specifications

2 Analog Inputs
Maximum Sampling rate: 4 MSPS
Analog Bandwidth: 200 kHz
Resolution: 8 bits
Input Impedance: 1 MΩ, 15 pF
Buffer size per channel: 4096 bytes
Input Voltage Range: -14 V to +20 V

Arbitrary Waveform Generator Specifications

1 Analog Output
Maximum conversion rate: 1MSPS
Low pass filter: 50 kHz
Resolution: 8 bits
Output current > ± 7 mA
Buffer size: 512 bytes
Output Voltage: ±4 V

The design of the electronics is ready. The firmware will be similar to the Xprotolab's firmware, with the addition of the watch specific functions. The second revision of the PCB is ready.

The PCB is a four layer board (Fig. 4). Most resistors and capacitors are size 0603, and some ICs are not in the tiniest package available, so there is room for improvement for the next version. The PCB assembly has been modeled in 3D in order to design the enclosure.


Figure. 4.	*Oscilloscope Watch PCB Assembly*

Gabriel Anzziani

My name is Gabriel Anzziani, I am an electronic engineer from Venezuela, graduated in 2003 from University Simón Bolívar.

I founded Gabotronics in February 2009, I chose the name of my company when I was very young, when I started playing with electronics (mainly dissasembling toys and electronic stuff to see how they worked).

Gabotronics is recognized by Atmel as a Third Party Vendor.

My main interests (besides electronics) are music, chess, and biking.

powerelectronics.com