Design Decision

Side Project:

I am moving forward with the Compass toy prototyping.  I am designing a simple breakout PCB for testing the display. I may put the display breakout for sale on Tindie.

Project Intent:

The primary goal of this project/blog is to show electronics design start to finish.

The design goal is an inexpensive in circuit chip programmer that will work for most devices available.


The Raspberry Pi Zero was released November of 2015 at a price of $5 US each.  I even got one with a copy of MagPi.  To Make it run any code at all, it needs a power supply and microSD card.

Of course I could continue with the current design.

Common components:

Both the Raspberry Pi and the current design need the following components.

Printed Circuit Board
Battery for power supply and charging circuit
Vpp Supply
Level Shifter Circuit
External ADC(Still undecided for current design)
USB to serial Bridge (not sure it’s necessary for R Pi)

Additional components for Raspberry Pi:

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Level Shifter Research


My ADC feature request on Espressif’s BBS has had 118 views. Unfortunately no word from the developers.  This might mean I have to add an ADC chip to the design.

The problem:

I’ve been thinking about the level shifter and why it was causing my software to crash. 10M Ohm and 10pF capacitance are very small loads. The software crashing just because a scope probe is connecting is very bad.(stating the obvious)

The hypothesis:

Bidirectional level shifters are typically designed to react quickly to transitions and drive very weakly in the steady state. With the target pins unconnected the shifter is steady state and the scope probe might be enough to cause a problem.

The Experiment:

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I have received a reply on the Espressif forum that gives a few suggestions.  The suggestions did get me thinking about the problem in a new way, I’ll see where this leads.

Moving Forward:

I have not been very motivated to work on this project.  The lack of feedback makes me wonder if anybody is getting any value out of what I write.  I have been very busy in my Embedded systems consulting business. I have worked on it for over two years now.  I feel like I have hit two significant roadblocks.

I have decided to fight this lack of motivation.  There are a few things I do when I am struggling with motivation.  There is a song by Martina McBride called “Anyway”, I like to play it when I am feeling discouraged.  I also saw a couple of Ted talks by Brene’ Brown about vulnerability and shame that I like to revisit.  They remind me that the risks I take in putting my work out to the world have intrinsic value.

Vulnerability is the birthplace of innovation creativity and change. — Brene’ Brown

Man in the Arena

The Roadblocks:

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