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Sunday, 28 May 2017

Video of DRO Operating

Video of DRO Operating

I've made a little video of the DRO operating so you can see how fast the update rate is. It's several readings a second and easily fast enough for anything I do. The gauge data stream is pretty fast and all six channels are read by the main processor over I2C, only three are displayed.

The main TFT is quite slow with big updates, but just about responsive enough when I use the menus.

One thing I was worried about was the auto power-off that the gauges have. After a period of inactivity they shut down, but fortunately all they do is turn the display off. The data stream continues, which is perfect for a DRO like this. It also might explain why the batteries go flat so quickly...

Tuesday, 16 May 2017

Latest OLED Watch (Isn't OLED)

The OLED watch project started when I saw some small OLED displays on ebay and thought 'What can I do with that?'. The watches followed, but there was always the problem of the power consumption of the display. I manage about 400 hours of use from a rechargeable 2032 battery, more from a non-rechargeable (the capacity is higher).
So, I had a look around and found a lower power display, one of the Sharp memory LCDs. These are very low power LCD displays.

A redesign of the hardware to drive the LCD was needed as the display isn't I2C, it's a serial bit stream. The hard part of using this LCD was finding a way to solder the 0.5mm pitch connector on to a PCB. Milling that connector was challenging as well. In the end I got a new soldering station so I have hot air. I also have a stencil for solder paste application. As well as milled PCBs I had a few made up by Dirty PCBs so I have a full solution if I need it.

The code was adjusted and the display was up and running.

The PCB is reversed due to the layout of the display connection. It's a cleaner look, but less interesting. I may revisit that in a later iteration.
The battery has also been reversed.

The overall watch is as thin as the OLED one and is very wearable.

So far the battery life seems to be far in excess of the OLED watch. The display update takes 20ms and to get power consumption to an absolute minimum the display is updated every 5 minutes. I'll see what real world battery life I get from this and then decide on what update rate I'll settle on.

Friday, 5 May 2017


Microprofessor MPF-1P

I recently bought an MPF-1P, which is an old Z80 training board. The one I got was in a bit of a state. The crystal had been removed, as had the processor. There were no ROMs and the 7805 regulator had also gone. The display power supply wasn't working as a transistor had blown.
These old bits of kit are very fixable, as the schematics are findable, and the PCB is all through hole technology.
I had all the parts I needed to fix the MPF in my parts bins, and got to the stage where the display had a scanning across all the digits. When the reset key was pressed the scanning stopped. I had found a ROM image online, but it had 'BAD DUMP' next to it, which was suspicious. I put out some feelers via email and on a forum (EEVBlog) and within about 5 hours I had a reply that listed a site which had many images and files. One programmed 2764 later and the MPF is alive:

I have some other images I'm going to try, but unfortunately I found that my old EPROM eraser no longer erases. I think the bulb has gone. As it's cheaper to get a new eraser from China than buy a new bulb (if I can foind one), I've ordered a new eraser. It'll arrive in about four weeks I'd think, so things are on hold for a while.

After this success, I thought the keyboard deserved a clean: