The PIC HomeCockpit Controller (PHCC) Motherboard
The PHCC motherboard is the core component of the PHCC system. It connects to the computer via serial port (RS-232) or via USB.
A PIC18F452 microcontroller is used as the "heart" of PHCC. It is responsible for communicating with the PC via a simple protocol and it scans the Analog inputs as well as the keymatrix every few milliseconds.
The motherboard houses the following subsystems:
- 35 analog inputs (3 priority, 32 normal) in form of a pinheader with 3 terminals for each analog input
| Potentiometers with a rating of higher than 10K Ohms is discouraged. This is because the input impedance of the analog-to-digital converter on the PICs is 2.5kOhms.|
The higher the potentiometer resistance, the more time is needed for proper conversion. With longer conversion times, the scanning rate goes down and has the potential to cause timing delays on reads.
- 16 connectors for 16 keymatrix daughterboards (64 inputs per board). For IDC flat ribbon cables.
- a RS-232 serial port (for Null Modem cables) with level converter (MAX232)
- a socket for USB interface board
- an I2C port
- a connector for Output daughterboards of "Type A" (DOA) using a 2x5 pinheader for IDC flat ribbon cables.
- and a connector for output daughterboards of "Type B" (DOB) using a 2x5 pinheader for IDC flat ribbon cables.
Schematic and Layout
Current revision (Rev.4B) of the motherboard (Sept 28th 2004):
Revision 4 schematic and layout (Aug 16th 2004):
See download page
Note about Resistors: all resitors are standard kind, ie. 1/4W, carbon film, +/-10% (Its generally a good idea to get lots of 10k and 330R resistors. the 10k are for pullups, the 330R for LEDs)
North American Bill of Materials Media:Motherboard rev4b BOM.pdf
The Rev.4 boards as sent to the boardhouse have a tiny mistake:
The numbering of the capacitors skips C8/9.
Changes between Revisions:
|Rev.2||These were never finished/fully routed boards. They were results of tests of either trials of how to run the traces or with different chips.|