The past few weeks have been very discombobulated with lots of heavy priorities and travel interceding in my project plans. And project progress has been stubbornly slow. However my second PCB arrived and it looks good.
This card is a QWERTY keyboard for the micro:bit. It needs a PSoC4 MCU to read all the keys and output ASCII using SPI because the micro:bit doesn't have enough I/O pins on its own.
Of course it is also one of those things that didn't go as smoothly as I had hoped. After spending lots of time troubleshooting, I don't think there is anything wrong with the design which is a relief, but how come it didn't just plug and play? I tend to be pretty meticulous with my designs and it pays off in them pretty much always working on the first power-up. But when they don't work first time it seems much tougher to troubleshoot - you know you already rechecked everything multiple times during the design phase so what could possibly be wrong? It turns out a little assumption can end up costing a lot of self-doubt and endless rechecking, oscilloscope testing and head scratching. In this case I had set the LCD contrast so light, there was no discernible activity on the display. I'm happy that is what the problem was, but not happy I spent so long to figure it out. Here is a video of the first signs of life from the new PCB...
The card is designed to have an alternate configuration with its own LCDs and a Bluetooth radio, making it a stand-alone Bluetooth terminal. This configuration will be implemented first because it doesn't depend on the micro:bit firmware also working at the same time. The micro:bit variant doesn't need Bluetooth of course, because the micro:bit has BLE built-in.
I keep promising to write a blog about Stirling engine technology, but it always seems that getting something working has higher priority - maybe next time...
This project it starting to look like there is a lot to accomplish in the time remaining, but at least there is progress.
Upcoming blogs:
- the micro:bit keyboard
- how Stirling engines work
- start connecting some sensors to the PSoC6
- designing the sensor interface PCB
Related Links:
Bluetooth Unleashed Design Challenge
Bluetooth Unleashed Design Challenge: The Challengers
Bluetooth Unleashed Design Challenge: About This Challenge
Links to other blogs for this project:
Stirling Blue - Project Description - Blog 1
Stirling Blue - Unboxing Hero - Blog 2
Stirling Blue - micro:bit TXTR - Blog 3
Stirling Blue - Fuel Measurement - Blog 4
Stirling Blue - Interface Description - Blog 5
Stirling Blue - BBC micro:bit LCD - Blog 6
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