Thursday, February 19, 2009


PIC32 controller – OLED

On my last post I detailed the basic outline of the new controller board, one significant part was missing from the complete assembly, the OLED screen.
Since this is the main interface I thought it might be worth doing a few notes of the kind of stuff we are putting out.
The last couple of images are of the Windows application that controls the USB Boot loader.
Its very easy to use.

First step is to power up the controller board while holding down one of the switches, this initialises the USB interface and displays the screen message.
Start the windows application and if the board is in boot mode it links in.
Once the coms are up and running point the application at the HEX file and download.
Resetting the board allows the new file to run.

The top pictures show the screen activity during normal running, the BfB logo on power up followed by the run screen.
The run screen is showing Firmware version number followed by the tool type found. We use an analogue input on the board to read a static voltage returned by the device attached to the tool header. The voltage is prefixed with a resistor that is unique to each of the tool types that may be fitted.

In this instance it has found the device attached and returned its type.
The tool type is used throughout the code to enable appropriate control.
Top of the Blue section of the screen shows the file being run is MINIMUG.TXT, this field changes as we jog through the contents of the card. The “Open” flag indicates the file status.
Below this we see the machine is in AUTO mode running the txt file from the SD card. We can switch this to MANUAL at any point and move the head using the axis buttons.
G_Code Line needs little explanation, it simply is a running line count of the G_Code lines executed.

A solid bar below G_Code Line represents the print progress, we can see at this point we are at line 3687 in the file and this is just a bit less than half way through the print. The bar reaches the right hand side of the screen when it gets to the end of the file.

The shorter bar below, is a representation of the step buffer contents, this line flicks side to side as the fill status of the buffer changes. The status is reported just before the code renters the Bresenham routine where its contents are replenished. As it stand it looks like the buffer is still about 25% full after preparing the next line ready to run. I don't know if I will leave this in, it was useful during development to see a more or less real-time status indicator, there are probably more interesting things to show on this line.

The temperature reading at the bottom is the current extruder temperature,measured by the thermistor, its low as the pictures were taken with the board on the bench during test.
One thing to note is that the screen is small, the pictures make it look huge, the actual size is about 25mm wide x 15 high (128 x 64pixel.)
For those with an interest in the screen, the contrast is fantastic, the text is small but very crisp and clear.

Screen images like the BfB logo can be changed quite easily, basically if you have a 128x64 bit map file in line art, single bit colour depth, I have written a short program that reads the standard file and outputs a text file containing the bitmap translated into a Byte array that plugs directly into the code. Any picture on the screen in 10 mins. There is loads of memory spare so you could even play with animations!

That about wraps it up, Ian has designed a Laser cut protective shield that fits over the display, this has some nice little extensions that bring out the buttons and a window for the display.

I forgot to ask in the last page. You guys ship the electronics fully assembled but only with the whole kit. By any chance, are you going to sell the electronics as a single item as well. So people can make their own parts but use your electronics. You'll still make money off of it, but it will make construction much easier for more laymen people who have already producing repraps in their area and the only thing that scares them is the electronics.
The electronics will be available as a separate item or even for those who want to build it, an electronics kit.

It is shown as part of the RapMan as this is the complete product available as a kit from BfB. I know Ian has been working on the web site so I would expect to see a few more things up there in the near future.

The priority for him is to cover the orders for the machine then in the next few weeks we can sort out the other bits and pieces.

I keep saying “we” as the board has been developed in collaboration with BfB. I do not work for them, for me its just a something I choose to play with in my spare time. I have no financial arrangement with BfB. What I have been given is more or less unlimited access to their parts and new machines as they have been produced, for this I am indebted to Ian as without his help there would be nothing here to talk about.

I hope from this you and others will see that this project is not about making lots of money. The source code needs to be available for people who buy the kit, we literally have not had time to even think through the practicalities of how we go about this. I would like to thank all the contributors to my last blog, it fired off in an unexpected way, I now have a much better idea of what the issues are.
"The electronics will be available as a separate item or even for those who want to build it, an electronics kit."

Any idea of what sort of prices you'll be looking for on those offerings yet? I expect that you should get a LOT of interest from folks who want to build reprap machines but who are intimidated by electronics.
Thanks again for your comments.
Regarding the price of the board alone, Ian has borne all the cost in getting the boards produced and populated, and I don't have those figures. I think its only this last week when he got the final materials list together and I have not seen him since then. Keep an eye on their web site I am sure they will put something on there soon.

Just to pad out the ideas we have had for the board. We are thinking possibly two versions, one fully populated and tested, and if there is demand for it, maybe a lower cost one with the PIC chip soldered in place and tested with other components supplied loose.
Will these boards be populated by someone manually, or will there be a more industrial process? As an industrially-produced board in large quantities from China, I suspect the board (at least without the OLED) shouldn't really cost more than 50 quid or so. As a small-production-run essentially prototype-made board, I think the price should still be competitive (certainly given the features) with the old price for a complete RRRF kit of $150.

If it turns out that, say, the electronics board is half the cost of the 750 pound full kit, I think personally I'd source electronics elsewhere.
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