■ PHOTO 1. If you don’t have one of these, get one. The
PICkit3 is programming and debugging you can carry in
your shirt pocket.
USB portal is not to be powered from an external source.
This is where universal comes in. By allowing an alternate
input to the 3. 3 volt regulator, you can nix the USB portal
and use the D+ and D- pins as PORTC I/O pins while
sourcing power from an external power supply or battery.
The same idea goes for the 32.768 kHz crystal and its
load capacitors hanging onto RC0 and RC1. If you have
plans for the real time clock/calendar, pads for the
required 32.768 kHz crystal are there for you. If you run
with Mick Jagger and time is on your side, you gain two
more PORTC I/O pins by simply not mounting the crystal
EDTP Electronics, Inc.; microSD Card Interface;
USCM-46J50: www.edtp.com
and supporting capacitors.
I didn’t double-label the OSCx pins. However, you can
choose to use the PIC18F46J50’s internal oscillator which
would allow you to use OSC1 and OSC2 as RA7 and
RA6, respectively. The pads for the 12 MHz crystal and its
supporting load capacitors can also be left blank if you
don’t wish to use the particular type of FOX crystal I’ve
designed in.
The ICSP connection is designed to be used with a
Microchip PICkit3 like the one pictured in Photo 1. If you
don’t have a PICkit3, you’ll have to lash up an adapter for
the programmer/debugger of your choice. The MPLAB
Real ICE, MPLAB ICD2, MPLAB ICD3, and MPLAB PM3
programmers/debuggers are all supported if you can cable
them in. The ICSP interface will also directly couple to a
PICkit2.
I’ve added filled planes on the top and bottom sides
of the daughterboard in Screenshot 4. Both planes are
ground planes. Note that I have used various thermal feed
through pads and vias to electrically connect the ground
planes and their associated electronic components. For
instance, you’ll find thermal connections that electrically
1
2
3
4
5
6
1
2
3
4
5
6
VBUS
C3 100nF
MINI-B USB RECPT
34
35
36
37
38
39
40
41
42
43
44
CS
RC5/D+
RC6/RP17
RC4/D-
VUSB
RD0
RD1
RD2/RP19
RD3/RP20
SCK
NC
Y2 32.768 KHz
C8
U1
C7
12pF
SDO
SDI
23
24
25
26
27
28
29
30
31
32
33
VDDCORE/VCAP
RA5/RP2
RE0
RE1
RE2
VDD
VSS
OSC1
OSC2
RC0/RP11
NC
Y1 12 MHz
C6
20pF
3V3
3V3
PIC18F46J50
C4
100nF
C2
22
NC
NC
RB4/RP7
RB5/RP8
RB6/RP9
RB7/RP10
MCLR
RA0/RP0
RA1/RP1
RA2
RA3
13
14
15
16
17
18
19
20
21
12
C1
10uF
VBUS
EXT-5V0
C10
4.7uF
VR1 TC1262-3.3
1 IN
3V3
3V3
3 OUT
3V3
1
2
2 COM
C9
4.7uF
C2
SDO = MISO
SDI = MOSI R1
10K
R1
10K
5
R2
330
1
EN
SDO
2
4
IN
U1
MC74VHC1GT125DT
3
SDI
3V3
SCK
CS
ICSP
1
2
3
4
5
6
3V3
microSD CONNECTOR
1
2
3
4
5
6
7
8
EDTP microSD INTERFACE CARD
56
November 2010
