Category Archives: Tech

NodeMCU (ESP8266) IO Pin State During DeepSleep() Going High, Low or Inbetween

Not a long post, but something I found little reference to.

I have been working on a project that uses the NodeMCU v1 board to drive a couple of transistor based outputs. The project uses a battery, so I was keen to keep the module in DeepSleep() for as long as possible.

It turns out however, that contrary to what is stated in the ESP8266 datasheet – the GPIOs do not hold their state through DeepSleep(). For me the pins I was using went high during sleep, turning on relays and LEDs galore.  I found that a fairly stout resistor would pull them back down during the sleep, without impacting normal operation – but this added a couple of milliamps to my sleep current, and seemed wasteful to have the board sit burning current in a resistor.

A little exploration found, for me at least that D0-D4 would always go high during sleep, but D5-D7 actually held their state. So far this has worked for several weeks, and quite a bit of testing.

So if you are having this problem, maybe try using the higher numbered outputs!

My thanks to RADARC & Members

Recently, I gained my foundation amateur radio licence with the help of the fantastic Reading & District Amateur Radio Club. Their course was practical and not too formal, with a great sense of what was required, and what was “required hoop jumping”.

There is broad membership, young to old and a good community feel – and certainly enough anecdotes to keep anyone busy.

I am looking forward to attending some meetings, and moving on to intermediate in the future, for now, I need to wait for Ofcom to update their database so I can claim a callsign!

Technical Fixit : Comfort Curve 3000 Keyboard

While at the local supermarket, I happened upon a reduced, but brand new in box, Microsoft Comfort Curve keyboard. For a few quid, I was not one to argue and gleefully stuffed it into my trolley, After all the Tesco value keyboard I had been using  was well past its hygienic and useful life.

When I got home, I happily ripped the PS/2 keyboard off my desk, re-routed my USB hub and plugged in the new item. For a few minutes everything was good, until of course I tried to use the S and A keys. It was at this point my heart sank, the keyboard was faulty. My mind was awash with predictions of trial by fire when trying to return and end of line, reduced item which only cost a few quid. Having worked in retail, I knew the £3 keyboard was not worth the petrol to get back to the store.

At this point I figured I may as well rip it apart, maybe I can solder something to get it working again, my oscilloscope is always sat on my desk ready. You can imagine the shock that came, when after removing around 25 screws, I found no PCB in sight. I suppose I should have known from the outset that a modern cheap keyboard would have some fancy internal workings, I was greeted with three plastic films, covered in a conductive web.
Keyboard Internals

Upon closer inspection, the problem is obvious, someone has nicked the film when assembling the keyboard and cut the sensor current to the feed pads. A quick lick of the finger and a broad press across the area confirms the problem . How a keyboard got past QC with two keys failed I don’t know ! I stopped for a moment and thought, then grabbed an old woodwork pencil on my desk, a little colouring later and a quick test and the keys are alive again !

Keyboard Internals

A few million screws later, and I have finally saved myself a few quid ! From writing this post, I can also confirm the keyboard is pretty nice to use, and the Windows key mappings printed are quite cool! Not to mention it has a calculator button, a total requirement, at least for all my future keyboards.
Keyboard On Desk