Looking for Pi display to use in direct sunlight

Chris,

If an update rate of, say, 30 seconds is adequate, and a 74 mm diagonal is adequate, you could look at the Pimoroni Badger - 296 x 128 pixels. Available plain, or with embedded wireless:

E-paper is the correct technology

E-paper up to around 400x300 is not hard to find, but 7" is a bit harder.

- 4 and a bit inches

This is a great compromise between teeny, and silly money

No, sadly those E-Ink displays are too slow. I don't need really fast refresh but I do need to be able to refresh in, say, 100mS (or maybe a bit more).

How about this ?

Do you need to refresh the whole screen? Many of the e-ink displays are able to do a partial refresh in much shorter time.

The Pixel Qi company went bankrupt in 2015, and while supposedly this one has the rights to manufacture and claims to do so:

However it is possible to buy the 7" panels on Aliexpress:

The Adafruit 10.1" panel is also available, for a higher price:

The 7" is about 2W in 100% backlight and 0.5W in 0% backlight, so not as low power as e-ink, but acceptable if you don't need such low power consumption.

Almost tempted to get one to play with, if only I had an application...

Theo

Will they really not do that speed? Shame, I like e-ink

The fastest (E-ink Carta) are around 450ms for a complete refresh which is OK for turning pages in a book.

Mmm. But aren't they essentially pixel level addressable, so some smart software could keep a RAM copy of a small display and only update the changed pixels?

Not thinking of running videos, y'know!

No, I don't need to refresh it all. The only relatively fast refresh is for the rudder position indicator which would just be a single dark cursor (or similar) moving about.

Power isn't an issue for me, it's on a canal/river boat with (relatively) lots of 12 volt power available.

My Kobo reader feels much faster than that, pages turn in what feels like a (significant) fraction of a second.

On Sat, 29 Jul 2023 10:18:46 +0100, The Natural Philosopher snipped-for-privacy@invalid.invalid declaimed the following:

SPI is NOT an old-fashioned serial UART. Depending on hardware it can run at MHz bit rates.

I am fairly sure that you can update on a per pixel basis. If you maintain an in memory copy of what you have *and* what you want, you can rip through and compare them and only send the updates.

I suggested e-paper because its very good in bright sunlight - less so in the dark. Not because of its amazing power consumption.

Personally I think it would do the job, but you would need to code some fairly low level 'set a pixel, clear a pixel' type stuff. And then build some graphics libraries on top of that to move your rudder indicator.

A really small one would suit my room thermometer app. Tempting..

Rip any dial out of a modern car and replace the fascia. They are all 'digital'

Or use PWM on a model R/C servo.

No, it's an approach that I'm seriously considering. As the 'transducer' at the rudder end is simply a pot stuck on top of the rudder post the whole thing can be analogue. I'm actually thinking that an edgewise meter might be best.

If you decide to use e.g. a radio control servo, there are very inexpensive 'servo testers' which do in fact have a pot in the middle. The whole lot could be had for just a few dollars. You could wire your pot up to them. Or generate your own PWM with a pi - the servo spec is a

And every time the servos dies its trivial money these days to plug in a new one

Analogue meters don't come cheap or with suitable scales these days. And thay are soewahtt fragile.

It's not an old RS232 port! SPI is clocked up to 250MHz, and it's used to drive many types of display on the Pi, including LCD and OLED, which are much quicker that e-ink.

---druck

If you want to use a servo to move a nice, big rudder position indicator, another low-cost option is to use a PICAXE device to drive the servo.

The PICAXE-08M2 is a simple, cheap 8-pin DIP package with a serial port that's used both to load programs, which are written in a simple integer compiled BASIC, and to accept ASCII strings containing textual commands and/or integer values. All PICAXE models have built-in firm-ware to drive radio control servos. There are bigger chips, i.e. have more i/o pins, but those are likely to be overkill for this application.

The BASIC compiler/downloader can be run on an RPi, though you'll also need a PICAXE USB Download Cable £14.99 inc. VAT, though most users only need one of these: it connects to an RPi USB socket and has a 3.5mm coax jack at the PICAXE end.

They also sell prototyping boards with a 3.5mm socket: an RPi, BASIC compiler, prototyping board and download cable forms a fairly complete development and prototyping outfit.

Full details and prices are here:

Unless you go to hamfests, in which case you can usually buy great quality old ones for $5 or less. Ebay seems to have cheap Chinese ones in the $5-$10 range too.

Well they _might_ not survive being dropped on the floor, but then neither might a Raspberry Pi board.