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PIC16F886 is easily accessible, so you can compile ... I'll make a PCB from a schematic or a description of used ports .... it's worth adding a display backlight setting
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I would suggest some small modifications to Sacchetti's schematic (see the attached pdf): removed the external oscillator (not needed for this pic), added an optional ICSP header for programming (e.g. for pickit2/3), a reset button and replaced the backlight control by an external switch which IMO would be more practical since you don't need to navigate through the menus to turn on/off the backlight (and you can save some components). You would need to make the PCB layout with these two PCB schema with the only constrain of following the PIC16F886 pin connections of this one for the firmware to work...Comment
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the PCB schemeComment
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The PIC16F886 is a better, newer choice, than the 16F876 which is an old part.
Schematic looks ok. Having an ICSP header pined out to match PICKit2/3 is very handy.
Only suggestion I'd make is to bring all unused pins to through hole pads. Then it is easy to use these if ever needed or using this PCB for other projects.
I do add pads for an external osc/XTAL just in case I wish to run at higher speeds. This PIC will run up to 8MHz on internal but up to 20MHZ on an external osc.
Adding a few pads will not increase cost of PCB. A reason to make the PCB universal is typical minimum orders for PCBs is 5. Then only need one to build the detector. The other four can be then used for other projects.Comment
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the schematic is based on previous designs to be backwards compatible but IMO your suggestion is a better approach. It would be better to bring back the external oscillator, so that the pic can be replaced with other model without changing the PCB, put the LCD in 8-bit mode to be replaced by a GLCD (e.g. KS010
and move the switches to other pins. Maybe the battery (12V) could be connected to the voltage regulator to save an input as Sacchetti did...
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with this backlight switch a good solution I used in the previous VDI only minus the switch is mechanical and stands out from the keyboard and looks like thisComment
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it looks very nice to meComment
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this is a more generic schematic that should work with a broader range of 28-DIP pics and upgradable to a GLCD display KS0108 based, it might need some further improvements though...Comment
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Schemes are, in my opinion, demonstrative and require testing the prototype. VDI2 should have a large number and other characters that will be readable for people with poor eyesight ... I would add SW4 to turn on the backlight without PWM, ON/OFComment
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if you use an LCD there won't be any difference with respect to the existing vdi's based on PIC16F88/690, however, what this design addresses is to be able to use the xc8 compiler in free mode as the license is very expensive and the demo expires in 2 months. At the same time, it allows to use a graphical display and a broader range of PIC’s without redesigning the pcb each time the pic is changed. The size of the numbers and letters won't be any problem since you can always zoom in with any pdf reader at the desired size... SW4 is for resetting the vdi, e.g. you can press SW4 and then enter the menu without turning off the vdi or if it is not working, instead you have SW5 to turn on/off the backlightComment
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I was wrong with SW4 with SW5 turning on the LCD backlight, I thought SW5 turned ON-OF by PIC16F886Comment
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these schemes are final I can order PIC16F886 to perform prototypes to test in the field on my IDXComment
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yes PIC16F886 would be sufficient to drive a LCD, however, if you would like later to upgrade to a GLCD (more expensive) then probably a pic with more memory would be necessary. I added a small change in the schematic following waltr's suggestion to include also sacchetti's backlight control for version 2 since there will be now plenty of memory and it would be compatible with an external switch. If you would like to do some tests, you could also use the sample prototype 80x53mm I have just made, it can be improved if there are suggestions, only missing to adapt the firmware...Comment
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SW5 will be now pins 3 and 1 of Q1 in the new schematic, but any of SW1, 2 or 3 can be programmed to replace SW5Comment
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Compliments to the bold design ... my suggestions for changes will be given after the prototype and tests in IDX .... a good solution with this SW5 - you can use SW3 to turn on the backlight ... I do not want to power the system with + 8V only with BAT, in IMUT + 8V to be deleted, power the system with BATComment
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