Hardware selection UI

For flashing the devices it is very nice if you can have some form of UI and there are many ways of getting there.

Output:

  • Attach the device to a HDMI screen
  • Attach LEDs to the board
  • Attach an LCD screen or 7-segment display
  • Run a web server and access the UI on a phone or similar
  • Use sound as output
  • Use the usb gadget framework(e.g. allow to attach to the board with a phone and interact with the device)

Input:

  • No input, just flash what is on the system
  • Use different USB keys or MMC cards to flash different software
  • Add buttons to the design
  • Allow the device to connect to a server and configure the device online
  • Run a web server

Requirements: I looked at the different options and sometimes came up with more options but in the end I wanted something that can work standalone. The idea to have a standalone device that can be taken to evens really sounted very nice.

Here are other options I was thinking about and some reasons I did not follow up on them: Runing a webserver was not feasible because one also then needs do networking/discovery and I did not want to dig into that. I might have to combine this with a small display on the device as to publish the IP address of the device.

I also looked at using the HDMI port and hooking a keyboard to the device but that really started to become a cumbersome project(We might as well provide documentation on flashing devices from a standard PC).

I therefore settled for adding a screen and a few buttons to the flashing device

_images/ui_think.jpg

Choice of LCD displays

I looked a different displays that where present and available for the Olimex board. This is where a RyPi might have been a no brainer because there are probably many (but still quite expensive) display and solution present. Looking the available options and seeing that in many cases I would have to spend and additional 40 Euro would bring the cost of this “little” hardware project to something I did not feel confortable with specially knowing that one can buy cheap Android phones or tablets bellow that price range.

Device type price connectivity Size
LCD screen +- 40 euro cape quite big
LCD screen + touch pad +- 40 euro cape quite big
7Segment display few euro lots of wires quite high
16x2 char display 10 Euro i2c nice fit
Nokia 3310 display few euro spi slim fit

Knowing that the Lime also has an expansion board and an UEXT connector it was nice to see that there was an LCD3310 module and I (wrongly) assumed that the board would be plug an play We later also found that olimex is selling the display and corresponding connector on their website

_images/MOD-LCD3310-1.jpg