VDI-RODERICO

[kroman01]

I was wrong with SW4 with SW5 turning on the LCD backlight, I thought SW5 turned ON-OF by PIC16F886

[roderico]

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 backlight

[kroman01]

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/OF

[roderico]

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...

[roderico]

it looks very nice to me

[kroman01]

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 this

[roderico]

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...

[waltr]

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.

[roderico]

the PCB scheme

[roderico]

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...

[kroman01]

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

[roderico]

if you are going to buy a PIC16F876 then it would be better if you can get a PIC16F886 which has an internal oscillator, I can recompile the firmware for PIC16F886 with the free version of the compiler without any problem since it has double program memory and modify Sacchetti's pcb scheme accordingly, although the last option would have been better...

[kroman01]

I can use PIC16F876 with no problem ... whether this modification can be introduced in VDI_BL

[roderico]

the changes in the code are simple, however I tried to rebuild the firmware with the free version of the compiler and it does not fit in the P16F88 even removing metal names and other features. I also tried with the sdcc compiler and has the same problem. You could use a pic with more memory as Sacchetti (post #40) or else I could post the changes in the code and someone else with a valid license could rebuild the firmware...

[kroman01]

I do not use metal names that can be removed ... magnetic stones are in the range +83 interesting metals up to +65 ... setting on aluminum foil -5 to +5