Front panel pcb

[Muntari]

Hi Carl,

I have been working on a PI design for about 18 months or so and as part of this I needed a front panel design that could have programable function buttons and a simple 2 line LCD display. The panel has 8 push buttons and 8 pots and is based around the PIC18F258. The unit communicates to the main DSPic board via either an SPI or I2C serial connection (10 pin header).
It is in circuit programable via a 6 pin header. I have attached a screen shot of the draft layout (original was built on prototype board) which will be done over the next few months all going well.
I will post the schematics as soon as I can extract them from Protel DXP as a screen shot does not cover the entire circuit.

The purpose of this post was to see if there were any members out there interested in such a board.. If so, I will keep this in mind when tooling up comes around. I am not really into selling boards but just thought it may be useful for others too. If there was enough interest, I would consider having a few boards loaded (SMD parts mostly).

Anyway, I have attached a 3d screen shot and will follow up with circuit in the next day or tw when I extract from DXP.

Regards

Brian K

[Carl-NC]

Looks interesting! Why so many pots?

[Unregistered]

More position options than actual usage Carl.
Although, in my design I require Threshold, Frequency,PWM, Sample period,
Sample delay, Tracking and Coil Balance.
The push buttons are for Select, Mode, Auto, Tracking ,Clear, Up, Down (although I have toyed with using a pot for the latter).
I have left options open for final design as I still have a few field experiments to try with multiple coil arrangements that require signal tweaking.

I am sending this reply from work so I will give a more in depth overview tonight...I need Adobe Writer to get the schematic so I'm off to purchase this now.

Regards

Brian K

[Muntari]

Hi Carl,
As promised,
Here is the schematic of my PI front panel design.

I have added a couple of opamps and zero ohm resistors to allow off board analog signals x10 gain.
Thought this might be useful for other folk with perhaps you front end boards.
I only use the serial SPI for my DSpic main board so a lot of parts can be left off.

Any comments welcome.

Sorry for the short explaination but i have tried 3 times to post this and until this try, the pop up add blocked killed my post....ah well.

regards

Brian K

[Muntari]

Here is the final draft of my PI front panel controls.
Corrections made to ICSP programing pin pull down resistors and adding the headphones connection.

The PIC is progammed to convert via the multiplexers (4051) 8 ratiometric inputs from the pots and 8 pushbutton inputs switched to ground.
How many switches and pots are used is up to the user.
The 2 opamps are also optional but were included for those who may wish to use say Carl's front end board design to interface to the panel. The Gain of both amps is 10 but can be changed to suit. They are both AC coupled but again, you could as easily replace with resistors.

The main purpose of this board however, was to convert user input from pots and transfer the position value and switch status in serial packet format to the DSPic based main board where all the grunt work is carried out for my particular PI design.

The LCD is simply for menu display and setup data in my application but one could readily program other features...bargraph etc.
The zero ohm links R35 and R36 are left off the board if using the OPamp inputs. Likewise C7 and C8 are left off if using the board with SPI.
You can still use I2C and Opamp features together without any conflict however.

The pot scaling resistor values can be changed to suit whatever but as shown the scale is from 0-4.9v or there about.

R7 can be dropped and just have R4 as a pullup for the switch to ground push buttons. With R7 in circuit the input is ranged from 0- 2.5v.

The LCD backlighting control can be PWM, push to activate via switch then turn off after delay or both.
The headphone jack is simply a feedthrough from the DSP baord via J5.
There is plenty of decoupling caps which should NOT be omitted.
The 5 volt reg is capable of 1 amp and could have been a 78l05 but I decided to up the current and include J3 for those who might want 5v off board.
LK1 and LK2 select pot or OPamp for feeding to multiplexer inputs.
You can drive a Mosfet from any of the port pin header connections with suitable drive transistors. I did not include these on board but could if enough people are interested.

Sorry Carl,
Just realized
I should perhaps start another thread under schematics which would be more suitable for this type of post.



Regards

Brian K.