Project Greenback, Mission Impossible and a new $29 display from 4D

Tubular

Greetings all,

Here's my first attempt at a low cost, "garage etchable" pcb for the prop. The aim is to sell the pcb for $1, and will be single sided in green solder mask, with just a few wire jumper links under the prop. If you can't afford the $1, you will be able to download a 1:1 pdf for toner transfer or photoetching, and make it yourself.

The specs are:

• Fits a Hammond 1551K cheap, widely available case (80x40x20mm)
• Support for slim VGA output, or
• 4D systems new $29 uLCD144 128x128 colour LCD, and 5 way navswitch
• USB A female at top for "BradC" or "Micah" port
• Micro SD surface mounted on back (P24-27), or KB/MS via wires
• Regulator on back
• P0-15 can expand out the side using DIL or SIL header.

I'm currently wrapping up rev2, which will add

• Headphone amp, and 3.5mm 4 pole jack for TV & headphone out
• Microphone/analog sigma delta pickup as per prop demo board
• Spot for optional MAX155x LiPo charger and small LiPo
• power switch
• optional lasercut metal fascia, instead of plastic lid that comes with the box

Finally, since the uLCD144 can display video animations, I'm trying to work out a way to 'smoke' a sacrificial resistor, for that "this message will self destruct" mission impossible kinda feel

So why post about this before completion? 1) to request any feedback or possible improvements before getting the batch made, and 2) to bring attention to the new $29 display; Sparkfun have only 20 in stock but have not yet announced it, so get in quickly if you need one for this or any other project! http://www.sparkfun.com/commerce/product_info.php?products_id=10090

tubular

TonyWaite

This looks superb!

T o n y

jazzed

Very nice! Totally tubular!

Dr_Acula

That is a rather nice display - good find. More details at http://www.4dsystems.com.au/prod.php?id=121

Hmm - there is an sd card on the back. I'm looking at my dracblade board thinking
1) sd card on the display
2) no need for a 20x4 LCD display
3) no need for the propeller driving a VGA - use this display instead.

That frees up another 12 pins on the propeller. So the prop uses 2 for keyboard, 2 for eeprom and 4 for two serial ports. 24 pins free - what ram chip could you drive directly off 24 pins? There might be a few options there.

It could lead to a very simple propeller board with an associated external ram chip, one of these displays, and not much else.

I think you might be onto something very clever here.

WBA Consulting

Tubular, That is a beautiful design and I would love to use something like this as my "reader" for the data that my plungelogger creates when I do my Polar Bear Plunges. I just noticed the uLCD-144 on Sparkfun yesterday and was going to post to see if anyone had plans on using it with the prop. I have a uOLED-128-G1 that needs a new screen (vapors from curing superglue absorbed into one side of the glass) and that costs $30. I think I may spend my $30 on this screen instead. Are you using the uOLED-128 object from the OBEX? From what I could gather at first glance, it uses the same command set, so that should be possible.

The MAX1555 is an excellent addition, I have samples of the IC to make a "LiPoTwig" in the formfactor of my PowerTwig.

In regards to the case, I have made several obvious declarations in the past that I am a big Polycase fan. We use several of the enclosures for products at work and a few of mine use them as well (IE: the metronome I made)In regards to this type of project, they have a few cases that would work well. In particular, I am using the VM series and the AG series for similar projects. The VM series is meant to be handheld and you can get an optional rubber boot which makes the finished project look really nice. The AG-43 is meant to be a desktop case, but due to its curved sides on the top, it actually fits rather well in your hands as a handheld device (I have a near finished design of a propeller platform style layout that fits into the AG-43). I have an AG-43 and a VM-24 with red boot that is not currently "allocated" so I could send them to you to check out or you can just request samples directly from Polycase. They are really good about samples.
The other nice thing about Polycase is that they do machining and silkscreening in-house. So, if you would like to offer cases precut, they can do that for you and at higher volumes (50+) the machining cost is minimal. When I had a case that had 4 holes machined by them, the cost was cheaper per unit when I bought 50 machined cases as opposed to buying 10 at a time unmachined.

Tubular

@wba, those polycases sure look nice. Thanks for the links. I'm going to have to get some. The fact that they can machine them in a cost effective manner makes them appeal for production.

For this particular greenback project I don't intend to do any machining myself - users can do that depending on what connections they need. The hammond case won me over due to its low cost and really widespread availability - I can even buy them at a few of the local electronics hobby stores. The focus here is on minimal barriers to others adopting a prop.

The Max1555 is a very useful chip. Unfortunately it also seems very popular at the moment too, and widely out of stock with a couple of exceptions

@drac, you're right, you could certainly free up a lot of pins. The command interface is the same as previous (SGC for pre-defined serial commands), but there is also 4DGL language which lets you define your own programs or mini applications. The 4dgl ide has come a long way since I last used it.

It should be possible to use 4DGL to ignore the EEPROM SDA and SCL lines for the first 3 seconds while the prop boots, and take over after that, providing display, uSD card, and single 10 bit ADC access over the 2 eeprom lines. Might want to have a "write protect switch" on the eeprom, though, just in case.

@jazzed and tony, thanks!

tubular

Harley

Since the screen is 128 x 128 pixels, if one were to use 5 x 7 font in a 6x8 character space, that would provide 21.5 char/row by 16 lines. However, text spaced only one space from line above is difficult to read for long. So for lots of text it would be limiting.

I'd like to play with one for a while, though, for sure. I wonder if the micro SD card could be accessed very easily by an external device, say if it were reprogrammed to turn the access to the SD card over to a Prop?

Cute but tiny. Compared to the 4.3" LCDs (Rayman's) it would only occupy about 1/3 of the area of PSB Graphics Demo active region, about 1.5 x 2".