If you’ve had a look on my EasyEDA page (link on RHS), you will have seen two new designs for the mobile terminal (and a few others that I did while testing but never got off the ground)
The first design was to test a way of mounting the LCD into the case by providing a daughter board for the TFT to mount on as below, this provided a stable back for the TFT so sit on and as an experiment it worked quite well, however I will not be progressing the design as subsequent to making it we have decided not to use a TFT in our first version and will instead concentrate on a 128 x 128 GLCD which is fully sunlight readable.
From the two pictures you can also see that the daughter board mates with the main board using a standard 2.54″ header, the height being perfect for the case, though the barcode module is a bit too high and forces the TFT back to the bottom of the case which doesn’t feel as nice (its also upside down but that can be fixed in programming). Also the position of the WiFi chip is real bad (notice the improvised enlargement of the case!) It needs to be well away from fingers and other obstructions to get the best possible coverage, preferably at the top. In case you haven’t looked at the designs the PIC32 is under the main board leaving all the components quite well spaced. the 8 pin chip on the daughter board by the way was a PIC16 which handled the touch screen, it worked but it was a pain programming two micros, so scratch design 1 (for now)
The second board I had made was the GLCD board. I made some big decisions this month to push the project on and in the process took a giant leap backward in the case design!
However I have finally ordered 50 cases and 50 keypad overlays, the design of the second board supports this decision.
The case is 135 x 70 x 24mm and has 2 x AA batteries. I went to a chinese manufacturer and after two attempts found a company willing to modify their standard case with my min order qty of 50. Having the cut-outs was easy but getting them to put a transparent front for the reader was a real PITA, the transparent front added $200 to the total cost making it a smidgen over $500 for 50 cases or $10 each.
The keypad overlay (above) was a bit more expensive, coming in at just under $1000 for 50, this may be the biggest gamble but I need to get something made and at least this way I’m going to have something. (Note the bulls-i text at the top, this is because these first prototypes will be trialled at Indevin on their production system which is called bulls-i)
The next big order was for 50 barcode scanners. I eventually decided in the first version to go with the Marson MT700 module and these cost me $38 each for a qty of 50. The second version will probably use lasers but for the standard checklists the majority of the cellar-hands will be using, CCD is fine
The GLCD is an east rising ERC128128-3 which works in 8-bit mode and SPI, in the above design the keypad and the LCD will be using the 8 data lines, as a fallback I will use SPI
Even before the case has arrived I found a few problems with my circuit. As I am using 2xAA batteries I needed to boost the voltage up to 3.3V, the RN-131 had such a boost converter built in, so lets use it! however try as I might I have not got this to work, the manual seems a bit contradictory with the text stating to use pin 21 for the 3.3V output but the diagram and pin description saying not to use pin 21, I’m missing something here but I don’t know what! I may be back to using the ON-Semiconductors NCP1410 which provides up to 250mA (achievable with some power management) and works quite well.
Secondly I regressed to a smaller PIC32 chip I am not familiar with and made a few newbie errors with the design ( I wired up the secondary osc not the primary and cannot use ISCP when the GLCD is connected) the reason I regressed is its a bit cheaper, a bit easier to solder and their are 256K Flash/64K Ram variants which are now available but which were not before. Also the dimensions of the board are slightly out. I will work with the board as best I can but will need to wait for the cases to arrive to get some proper measurements and respin another. Did I mention I love EasyEDA by the way 🙂
Thirdly USR just released an $11 wifi module which is tiny! How tiny?
The centre module is the RN-131 (the one I’m using), the bottom module is a WizFi210, the module on the right is a TI CC3000 (a good choice but I don’t trust my antenna PCB skills) and the tiny little one on the left is the new WiFi232-S, the antenna looks a bit on the dodgy side but it may be worth a test, I now have 5 of them so it will be a worth while test for a potential $22 saving on the BOM!
So my current board is still not the final one!
I’ll leave the case pictures as a surprise (good or bad) for the next post!