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A Standard Camera and Electronics Pack

Posted: 07 Jul 2015, 11:36
by duerig
The diversity of scanners and cameras and controllers have let us explore the problem space rapidly. But it has also left us with a legacy of a huge number of mostly-working solutions that still require tinkering and expertise to get right. To help address this problem, I am proposing a standard electronics and camera pack. This is not meant to replace working setups. But for any new members or new scanners, this is a good default. Here is the shopping list:
  • 1x Raspberry Pi 2 (For control with Spreads)
  • 1x Raspberry Pi 2 Case
  • 1x 7-Port Powered USB Hub
  • 2x USB Mini B Cable
  • 1x USB Micro Cable
  • 2x Canon Powershot A2500 Camera
  • 2x AC Adapter For Camera
  • 1x SD Card Reader (For writing/updating SD Card Imags and for Kiosk Mode)
  • 2x 4GB SD Card (CHDK Images for Cameras)
  • 1x 16GB Micro SD Card (Spreads Image for the Pi)
  • 1x Power Strip (Surge protection, acts as a single power switch for everything)
  • 1x Small Mirror (For camera callibration)
I have been using this electronics pack for testing with the Archivist and will be offering it as a tested pre-configured kit on for those who want something that is more plug and play. But you can order and configure this set of components yourself for less money, especially if you look for refurbished or used cameras.

I've been working on a Spreads image for use with this standard pack. Unlike the nightly builds, it is based on Raspbian with a standard pi user. My Spreads image can be used as a network appliance just like the nightly build. But you can also plug a keyboard/mouse/monitor into the Pi and use it as a standalone kiosk instead. In either mode, you will be able to copy books off onto SD cards using the card reader.

This version of Spreads has been tested with a pair of CHDK images for the cameras. These images are already bootable and configured. The 'odd' image is for the camera that will point at the odd numbered pages and the 'even' image is for the camera that will point at the even numbered pages. For the CHDK images, unlock the SD card, write the image, then lock the SD card.

If you pick the hardware described here for your new scanner, then you should encounter fewer problems getting started. And when you do encounter a problem, I will likely be able to reproduce it because I have the same hardware. As others make scanners with this standard hardware, they should be able to be more helpful as well.

Regardless, more documentation is on its way. I will be documenting the quirks and potential pitfalls in this hardware setup. And I will also document more about how to use the mirror technique to calibrate your camera (see the Footsie Bookscanner thread for more discussion on this).


Re: A Standard Camera and Electronics Pack

Posted: 07 Jul 2015, 13:29
by vitorio
duerig wrote:
  • 1x 7-Port Powered USB Hub
When I upgraded the Austin Hackerspace scanner to an RPi 1 model B+ (same form factor), the additional USB ports meant I could do away with the powered USB hub (left camera, right camera, USB keyboard, USB extension cable for user-supplied USB stick; network connectivity is via Ethernet). Why do you need the additional ports?

Also, since it's in a public space, I found keeping a small level by the scanner was useful.

Re: A Standard Camera and Electronics Pack

Posted: 07 Jul 2015, 14:06
by duerig
There are minimal builds that wouldn't require a powered USB. If you are using it as a net appliance, you only need two ports for the cameras and one port for a wifi module (or skip the wifi module if you connect via Ethernet).

But I found the addition of a powered USB hub added greatly to the flexibility. You can plug both cameras in, plug a keyboard and mouse in, and plug a foot pedal or wifi module as well. It also means you have plenty of slots for USB drives or SD card readers to copy off scans.

One additional trick is that you can plug your Raspberry Pi into the hub *twice*. You plug in as the 'master', but you also plug in the micro USB power cable. This means you don't need to purchase or manage a separate USB power supply. Given that the hub replaces another piece and adds so much flexibility, I thought it was worthwhile to include it.

In the standard kit, you might be able to forego the hub, the SD card reader, the mirror, and the power strip if necessary. They all add convenience and flexibility. But you can get along without them if you need to.


Re: A Standard Camera and Electronics Pack

Posted: 12 Jul 2015, 23:05
by nafraf
duerig wrote: [*]1x Small Mirror (For camera callibration)[/list]
I have not experience with camera calibration, I don't know how to use the mirror. Is there any documentation for that?
If camera calibration means camera alignment, with CHDK it's possible to draw a grid on LCD, there are default grids on standard CHDK, and uses can define new grids, probably we can add that feature to spreads.
EDIT: Now I read the post about camera alignment :)

Re: A Standard Camera and Electronics Pack

Posted: 12 Jul 2015, 23:15
by duerig
nafraf, I am working on the documentation for this right now. For the discussion which prompted this, see the last several posts here: ... 5&start=30

As part of the instructions I am working up, I explain how to enable the grid in CHDK. That is *super* handy for this. :-) I am not sure that it needs to be part of Spreads itself. It is fine to just use the CHDK menus on the camera itself.

BTW, since you are the CHDK developer that I know reads the forums, do you have an A2500 camera yourself to test/develop with? PM me.


Re: A Standard Camera and Electronics Pack

Posted: 13 Jul 2015, 22:01
by duerig
I have created two new pieces of documentation. First, I wrote some explanation of how to put together the standard hardware kit, including how to create all the SD card images:

Second, I have written a step by step guide specifically about how to align the camera precisely. With this guide, you will be able to draw a fairly accurate crosshair on a mirror, place it at the center of your (Archivist) scanner platen, and then align your camera exactly to the center of the mirror. While the exact dimensions of the alignment cards I made are for the Archivist, you can adapt this method to any scanner.

I am now offering both an electronics pack (which includes the alignment kit) and a standalone alignment kit on if anyone is interested. But I have provided instructions on how to make these as well.

Let me know if you have any comments or questions or fixes on either of these guides or in the software.


Re: A Standard Camera and Electronics Pack

Posted: 11 Aug 2015, 01:12
by peterZ
im having a lot of trouble getting 2 x Canon Powershot A2500 Camera's

i have managed to get one, but can not get another a2500.....

i have 2 x cannon g15 powershot camera's , i assume these are a more recent camera, but probably more expensive.
is it possible they could be offically supported.?
'im prepared to give a donation to help make it happen .....

thank you

my shift key is not working ....

Re: A Standard Camera and Electronics Pack

Posted: 11 Aug 2015, 10:05
by duerig
PeterZ, it is getting harder to find A2500 cameras everywhere. Anthony Dong and nafraf have been working on a port of CHDK for the newer replacement model that is still in production. This will become the new 'standard' that I can help provide support for. When they are confident that their port works well, I'll announce it here.

In the mean time, you should continue to use your g15 cameras. There is already a CHDK port for them available. If they work for you, there is no reason to switch away from them. The idea of a 'standard' camera model is to provide something that is known to work well for people who haven't already chosen a camera yet.