Bitten by SI units

The USA is one of a few countries that have not fully adopted SI units (sometimes called Metric units) of measurements across the board. Generally for people working in the USA on electronics projects it is a small issue. We quickly learn whatever translation is required. However, sometimes these units do cause problems when the same digits represent different objects.

I was just bitten by this with the footprint of a capacitor on a PCB I was having assembled. I read the data for the capacitor and saw the footprint was “0603”, so I searched my footprint library and dropped in a “0603” footprint. Unfortunately when assembly was attempted the capacitor was way smaller than the footprint. A few minutes of research revealed the issue, what I had used was an “0603” inch footprint, the part was “0603” mm.

Not sure how may other numbers like this exist in both measurement systems for capacitors and resistors, however you can bet that in the future I will be triple checking that!

Isn’t it about time the USA joined the majority of the rest of the world and fully adopted the SI unit system:


The journey to a new product

Over the next several months I will documenting the development of a new tool for embedded system software debugging. The tool will be launched in 2018 on the Crowd Supply web site. The design, when completed will be Open Source Hardware and Software.

The first couple of stages have already been completed; earlier in 2017 a bench prototype was constructed to enable some basic research to be done. It comprised of a ST Microelectronics Nucleo evaluation board, a Texas Instruments wireless evaluation board and a breadboard to hook it all together.

Early prototype

As is typical of such breadboard prototypes some of the higher speed signals (for example the SPI interface) were a little unreliable; once the basic concept was proven the design of a printed circuit board was begun. The initial design is once again a prototype to provide a stable platform for the completion of the controlling software.

Prototype PCB

The first PCB is currently being assembled and I will write about the initial testing when it arrives.