My BLE module.
February 2014. There was a discussion on the B9Creator forum wether it would be advantageous to use something other than a fully grown PC/Mac to drive the B9Creator.
The device would at least have to offer a way to calibrate Projector and Build Table and print files. It would be good if you could select files - instead of i.e. reading the first file on a thumb drive - and edit print parameters.
There were some proposals the iPad one of them. I use my iPad on hourly basis, so this would not be an option - if I wouldn't still have my last generation iPad lying around.
So I decided to give it a try and do a Proof of concept - a project to show that an iPad could be used to control a B9Creator - or not.
The printer needs a VGA video signal for the data and an USB connection for control messages. As a mortal developer you can not "just connect" a device to an iPad using USB. You will have to use WiFi or BT 4.0 (Bluetooth 4.0 ) also called BLE (Bluetooth Low Energy). Cost wise BLE is cheaper so I settled for that. The Arduino in the printer converts the data received by USB to a serial data stream. Luckily you can overwrite this data-stream with your own, not very elegant, but possible.
From a different project I had BLE modules that provide a serial data-stream so I just added some interface circuit for level conversion - and to make sure the BLE module will be stronger than the USB module :) - made a little PCB (MCB would be more appropriate as I milled the board) and e voila there was a data connection.
The video connection was even simpler, because you can buy an VGA Video Adapter for the iPad.
Normally the printer electronics are supplied via USB. As USB wouldn't be used any more I used an power supply for an Arduino. As the power socket on the printer electronics couldn't be reached I added an power socket to the BLE module.
Total cost 7$ BLE Modul, 0,3$ interface chip 3$ connectors and cables 40$ VGA Adapter, 14$ power supply, Thats about 65$ not really cheap, but paired with the price of an iPad it is still cheaper than an PC dedicated to the printer.
I did a video showing the thing in action. It can be watched here. It's a bit longish. I might shorten it in the future - if you believe that, I will be happy to sell that bridge of mine to you. It's located in central New York.
March 2014. In the meantime I added Dropbox support and I replaced the Arduino power supply by an ordinary USB charger/power-supply that will be connected via an USB cable - cheaper and saves an connector. There is now a settings page and I made some other minor modifications.
The BLE module I use has two drawbacks, for one it is not commercially available and secondly it needs to be configured before use.
So I looked for an commercially available Arduino compatible BLE module and found one. But it didn't really work , it didn't proof strong enough to overtake communications, and it was also configured differently. To not waste it I modified and configured it, but found the connection to be not too stable. Probably because the shield (that's what the Arduini call their expansion boards) is mounted between to othe PCBs in the bowels of the printer.