VOTI Wisp648 User manual

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Wisp648
© VOTI – Wouter van Ooijen – 2007, 2008, 2009, 2010
last modified 30-MAY-2010
Content
Introduction 1
In-circuit programming 1
Programming details 3
Power 4
Serial pass-through 5
Firmware upgrading 6
Circuit description 7
Kit construction 8
Troubleshooting 13
Connector pin assignments 13
Connecting a target chip 16
FAQ 17
PCB 1.05 bug 19
Abbreviations and acronyms 21
Document history 22
Introduction
Wisp648 is a serial port in-circuit programmer for Microchip FLASH PICmicro microcontrollers.
The list of target PICs that are supported changes too often to include here, check the Wisp648
page at http://www.voti.nl/wisp648 for an up-to-date list.
In-circuit programming
In-circuit programming (often abbreviated as ICP or ICSP) implies that you program your target
chip while it is in its target circuit. There is no need to extract the chip from its circuit, put it in a
programmer, and put it back in the circuit after programming. Instead you make a connection (a
few wires) between the programmer and the target chip, and you can program it without even
touching the circuit.
To make in-circuit programming possible the target circuit must comply with some rules. The
details are explained in the Programming details section (p 3), but the summary is stated in the
table below. When a resistor is mentioned the stated value is a minimum (higher is OK), and any
circuit is OK that has at least the indicated impedance (for instance: an UL2803 has an input
impedance of at least 2k7, so it can be connected directly to PGC, PGD or PGM pins, which
require a minimum impedance of 1k). Pin 7 and 8 (RxD and TxD) are needed only when the Serial
pass-through (p. 5) is used. The colors correspond to the wires supplied with the Wisp648 kit (but
for readability grey is used in the table instead of black).

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Wisp648
programming
connector pin
Target PIC
pin Requirements
1 Ground (Vss) -
2 +5V (Vdd) When supplied by the target circuit: must be 5V +/- 5%, the
Wisp648 will draw less than 50 mA.
3 PGC Programmer connects directly to the target chip; 1k resistor
between target chip and rest of the target circuit.
4 PGD Programmer connects directly to the target chip; 1k resistor
between target chip and rest of the target circuit.
5 MCLR Programmer connects directly to the target chip; 33k resistor
between target chip and rest of the target circuit. The programmer
will ‘load’ this pin with a 1kΩresistor connected to a 22µF
capacitor. This might interfere with the applications’ use of this
pin.
6 PGM For chips that have a PGM pin, either:
•Target circuit pulls this pin low
•Programmer connects directly to the target chip; 1k resistor
between target chip and rest of the target circuit.
For a target chip that does not have a PGM pin this line can be left
unconnected.
7 RxD Optional, programmer connects directly to the target chip; 1k
resistor between target chip and rest of the target circuit.
8 TxD Optional, no requirements
The previous table stated target PIC pin functions, not the pin numbers, because the numbers of the
pins used vary from chip to chip. The table below works for most DIL chips, but the chip’s
datasheet is the final authority. Especially the UART pins (RxD and TxD) and the PGM pin vary.
Pin name 6/8-pin
chips 8-pin chips 14-pin chips 18-pin chips 20-pin chips New 28-pin
chips
Old
28-pin
chips
New
40-pin
chips
Old
40-pin
chips
Example
chips
10F2xx 12Fxxx 16F630
16F688 16F6x8(A) 16F88 16F690 16F689 16F8x6(A) 16F57 16F8x7(A) 16F59
Ground
(Vss) 7 8 14 5 20 8, 19 4 12, 31 5
+5V
(Vdd) 2 1 1 14 1 20 2 11, 32 15,35
PGC 4 6 12 12 18 27 16 39 12
PGD 5 7 13 13 19 28 17 40 13
MCLR 8 4 4 4 4 1 28 1 14
PGM - - - 10, 11* - 24 - 36 -
RxD - - - 7* - 18* - 26* -
TxD - - - 8* - 17* - 25* -
The first column, 10F2xx, refers to the DIP version of these chips. These chips are also available in
a tiny 6-pin SMD version (with a different pinout). The DIP version has two unused pins.
Microchip sells two popular programmer/debuggers, the ICD2 and the PICkit2. Beside the DB15
connector the Wisp648 also has two connectors that are compatible with these Microchip
programmers. These connectors lack the PGM, RxD and TxD lines, because those functions are
not present on the ICD2 and PICkit2. If you use these connectors it is probably to connect to an
existing board that is ICD2 or PICkit2 compatible, so the pin assignment of these connectors is of

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little interest to you. If you would want to make your own board with either of these connectors,
check Connector pin assignments (p. 13) for the pin assignments.
Programming details
Three pins of a PIC chip are central to programming the chip: MCLR, PGC, and PGD (and of
course +5V and ground). The MCLR pin is by default the reset pin of the chip. On newer chips this
pin can also be configured as an input pin. The PGC and PGD functions are often on pins that are
also I/O pins, on most chips RB6 and RB7.
On most chips programming mode is entered by the following sequence:
•reset the chip: +5V present, MCLR is low.
•MCLR quickly rises from low to Vpp (for most chips ~ 13V)
This sequence is called the Vdd-before-Vpp sequence. Vdd is the Microchip term for the +5V.
Another sequence, required by some PIC chips, is the Vpp-before-Vdd sequence, which is
described later. The Wisp648 requires (or generates) +5V. It can not be used with a lower voltage.
Note that MCLR must rise quickly. The exact timing requirement is in the programming
specification of each PIC, but it is such that no capacitor on the MCLR pin can be tolerated. As a
simple rule: the programmer must be connected directly to the MCLR pin, the rest of the circuit
connects via a 33k resistor (10k will often be enough, but 33k is recommended). A reset-delay
capacitor can still be present, but it must be on the other side of the 33k resistor.
When the chip is in programming mode PGC is used as clock line (programmer to target chip) and
PGD as the data line (bidirectional) to enter programming commands and data into the chip, or to
read the content of the chip. The programmer must be able to control these two pins: the rest of the
circuit must not load these pins too heavily. As a simple rule: it is OK when the programmer is
connected directly to the PGM and PGD pins, and the rest of the target circuit is connected via a
two resistors of 1k or higher.
The programming mode used by Wisp648 is called HVP for High Voltage Programming (because
a high voltage on the MCLR pin is used to enter programming mode). Some PIC chips support
another, more limited programming mode: LVP for Low Voltage Programming. To use LVP it
must be enabled in the configuration word in the chip. When so configured, one I/O pin (on most
chips RB4 or RB5) is now PGM, for ProGraMming enable. When this pin is high immediately
after a reset the chip enters the Low Voltage Programming mode. This LVP is not supported on all
PICs, and it claims one I/O pin, which for the popular 18-pins chips is right in the middle of the
only full 8-bits port. Hence LVP never became popular, and on newer PIC chips it is no longer
available. This would be of little interest to you as Wisp648 user, except for one bug which is
present in some PICs (but no-one seems to be able to tell in exactly which ones – it might even
depend on the silicon revision): when the PGM pin is high during reset this can interfere with high
voltage programming! This can happen even when LVP is not enabled in the image that is
programmed into the chip. The solution is to make sure that the PGM pin is tied low. This can be
done by adding a suitable resistor to the target circuit (maybe one is present already), or Wisp648
can take care of this via a pin in its programming interface. Note that the target circuit must allow
the PGM pin to be drawn low – if you connect it to +5V with 10 Ohm resistor Wisp648 will not be
able to pull it down. But 1k or more is OK. Note that this LVP problem is not specific to Wisp648:
whenever you use an HVP programmer with a chip that has this problem, you must take care to
pull the LVP pin of your target low.
Some PIC chips have a peculiar requirement for entering programming mode: Vpp (~ 13V) must
be applied to their MCLR pin and only after that the power (5V) must be applied. This is called the

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Vpp-before-Vdd sequence. Wisp648 can do this by generating the Vpp and then (very briefly)
shorting the 5V supply. This is done by the big transistor (TIP122) on the Wisp648 board. Some
target chips can not be programmed when this feature is active, and power supplies do not take this
abuse well, so this feature can be disabled. To disable it you must remove the jumper on the pins
J1. I suggest that you leave that jumper out by default, unless you are sure that all your power
supply(s) can handle this. Your power supply must also limit the short-circuit current to a
reasonable value. A few Ampere or less will be OK. All supplies based on 7805, 78L05 and similar
chips have no problem with this. The Wisp648 has an on-board 7805-based power supply which
can handle this shorting.
Power
The Wisp648 is designed for programming a target PIC which uses 5V power. The Wisp648 needs
this 5V too. There are two possibilities for powering the Wisp648 and the target circuit:
•The target circuit has its own 5V supply. Do not connect a wall-wart to the Wisp648; the
programmer will take its power from the target circuit.
•The target circuit does not (yet?) have its own 5V. Connect a wall-wart to the Wisp648; the
programmer will supply 5V to the target circuit.
Do not mix the two situations, when both the target circuit and the Wisp648 supply 5V a small
difference in the two voltages might damage one or both power supplies.
The Wisp648 has an on-board 7805-based power supply. To use this supply you must connect an
external wall-wart that supplies 9 .. 18V DC. An AC wall-wart might work, but only for a target
circuit that uses very little current (< 100 mA). The wall-wart connector on the Wisp648 is a
2.5mm centre-pin connector, which is commonly used for wall-warts. The centre pin is positive,
which seems to be the most common polarity. Unfortunately, about 10 other connectors (and 1
other polarity) are also commonly used for wall-warts. If you prefer a more permanent and stable
connection (those centre-pin connectors disconnect very easily) you can use the PCB screw
connector block. The + mark on the PCB indicates where you must connect the positive wire.
The 7805 is a linear regulator, so the voltage difference between the input (from the wall-wart) and
the output (5V under normal circumstances, but could be 0V when you accidentally short-circuit
the power) will be dissipated as heat. The 7805 is short-circuit and thermally protected, so it should
withstand all normal use. But it might get (very) hot when you use it to supply a large current,
especially when combined with a high wall-wart voltage. The temperature rise can be calculated as
Λ
t
= ( V
in
– 5.0V ) * I * R
th
Λ
t
= temperature rise in degrees Kelvin
V
in
= Wall-Wart voltage
R
th
= thermal resistance, for a bare 7805: 60
o
K / W
I = total current in A
With a common 12V DC wall-wart and 100mA ( = 0.1 A) total current the temperature rise will be
42
o
K, which is reasonably safe. For a higher current and/or a higher input voltage you might want
to attach a heatsink. A small heatsink might have an R
th
of 20
o
K / W, which rises the safe current
by a factor of 3. For a heatsink with a still lower thermal resistance the internal thermal resistance
of the 7805 must be taken into account (check the datasheet).
The Wisp648 contains a diode (D4, 1N5819) that will short the +5V power when it is supplied by
the target circuit but accidentally connected in reverse. This diode can handle 1A, probably more
for a short time. You of course will never apply power in reverse (I do), but just in case, it might be
a good idea to use a power supply that is current-limited to 1A or less. In fact 100 mA will be

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enough for most ‘beginners’ projects. Using a switching power unit from a PC is a very bad idea;
such a PSU can deliver currents that are more appropriate for an arc welder than for an electronic
project.
Serial pass-through
The Wisp648 can connect your serial port directly to the target chip. This can be very convenient:
after programming your target chip you can communicate with it, using the same serial port,
without re-plugging cables or other manual actions. This pass-through is done in the Wisp648
firmware, so it is limited to lower baudrates (up to 9600 baud seems to work OK). In-circuit
programming requires two wires data between the programmer and the target chip, so it makes
sense to re-use those two wires for serial communication. But the two PIC pins used for in-circuit
programming are not the pins used by the PIC UART, so using these two pins forces you to use
software (bit-banged) UART code in your target chip. The Wisp648 has two extra lines that are not
used for programming the chip, but can be connected to the target chip UART pins. This requires
you to make two extra connections, but now you can use the hardware UART in your target chip.
(That is, if it has one. Not all PIC chips do.)
Note that the two extra lines (for connection to the PICs UART pins) are available only on the
DB15 programming connector. The ICD2 and PICkit2 programmers do not have a pass-through
function, so no pins are available on these connectors for such a function.
The common asynchronous serial communication (as used by the PC serial port) uses RS232
voltage levels and polarity. These PIC UART pins use TTL (0 .. 5V) levels and inverted polarity
(inverted with respect to the RS232 line levels). A MAX232 or an equivalent chip is the standard
way to interface between the TTL signals and the RS232 signals. But some dirt-cheap PIC circuits
interface the PIC pins directly to the RS232 signals. This violates all design rules and
specifications, but sometimes it works. Note that in this situation the TTL signals have the same
polarity as the RS232 signals. Hence a PIC UART can not be used, because it uses inverted
polarity.
The Wisp648 pass-through function interfaces between the signals on its RS232 connector and the
target chip. Two choices are available:
•Use the programming lines (PGM and PGD) or use the extra lines (pin 7 and 8 of the DB15
connector)
•Use inverted polarity (the target PIC assumes that it interfaces to RS232 via a level/polarity
converter – MAX232 or similar), or use true polarity (the target PIC assumes that it
interfaces directly to RS232).
I recommend using inverted polarity: true polarity makes sense only for dirt-cheap circuits and its
reliability is questionable. The choice between using the UART or bit-banging the serial
communication on the PGC/PGD lines is up to you. The UART is easier to program, but the
UART is not present on all PICs, and it requires two extra wires, which are available on the DB15
connector only. Using the PGC/PGD lines requires more work on the target chip, but needs no
extra wires and allows the use of the ICD2 or PICkit2 compatible programming connectors.
When the target circuit itself has an RS232 interface and you want to ’take over’ this interface with
the Wisp648 pass-through feature a resistor must be inserted to make it possible for the Wisp648 to
‘override’ the signal from the RS232 level converter. I suggest a value of 1 .. 10k. Figure 1
illustrates this trick. It also shows isolation resistors between the PGM, PGC and PGD lines and the
rest of the target circuit, a 33k pull-up for the MCLR pin, and the mandatory 100nF decoupling
capacitor for the power.

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Figure 1 : combination of RS232 interface and serial pass-through
Firmware upgrading
The PIC 16F648A in the Wisp648 contains the Wisp648 firmware. This chip can not update its
own FLASH, so to upgrade the firmware you will need either another 16F648A chip or a
programmer that can program this chip.
If you have a second programmer that can program a 16F648A chip:
•Remove the 16F648A chip from the Wisp648
•Use that second programmer to program the new firmware into the chip
•Put the 16F648A chip back into the Wisp648
If you don’t have a second programmer you will (temporarily) need a second 16F648A chip:
•Use the Wisp648 to program the new firmware into the second 16F648A chip
•Remove the 16F648A chip from the Wisp648
•Put the second 16F648A chip in the Wisp648
•Verify that the Wisp648 works and has the new firmware (the PC application will report the
firmware version). You can now re-use the old 16F648A.

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Circuit description
Figure 2 : Wisp648 circuit diagram
Figure 2 shows the Wisp648 circuit diagram. The MAX232 chip in the lower left corner handles
the conversion between RS232 voltage levels and polarity, and the TTL levels and polarity used by
the 16F648A PIC chip. The MAX232 connects to the RB1 and RB2 pins of the PIC, so the UART
hardware of the PIC can be used. The LED (above the MAX232) is connected to pin RA4 of the
PIC, so the PIC can switch the LED on and off. Pin RA4 is not very useful for other purposes
because it is open-drain only (it can not pull itself high, only low). The LED can be activated
permanently by closing solder jumper J2. This could be done when the PCB is (mis-) used as 7805
power supply only.
The 16F648A (lower right corner) chip has a 20 MHz resonator (cheap, robust, no capacitors
needed) and the mandatory 100nF decoupling for its power. No MCLR pull-up is needed because
the chip is configured for internal MCLR (pin RA5 is available as I/O pin, but not used here).
The three BAT85 diodes and the capacitors C7, C8 and C9 are a charge pump. When the PIC
makes pin RA2 high, and then switches pins RB3 and RB0 high and low (180 degrees out of
phase) it will create 3 x 5V (minus some losses) on capacitor C9. This is the source for the

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programming-enable voltage Vpp. Transistor T1 is used to (briefly) pull the MCLR pin of the
target chip to ground. When T1 switches off the MCLR pin will quickly rise to the ~ 13V on C9.
Transistor T2 can (under control of the PIC, and only when jumper J1 is placed) short the 5V to
ground. While this is done the 16F648A PIC and the MAX232 run on the charge stored in
capacitor C10.
The circuit around the 7805 (top) is a standard 5V power supply. Two connectors are available to
connect a wall-wart. Diode D7 prevents damage when the wall-wart is connected in reverse. Diode
D5 protects the 7805 when the target circuit provides 5V power (a 7805 does not like to be reverse-
powered).
The resistors R1 .. R6 provide a minimal level of protection against misuse by limiting the current
that could result. They also damp ringing effects that could be caused by long wires.
Three connectors and a row of PCB pads are available for making the connection to the target
circuit. The male DB15 connector is a cheap and robust connector, and provides the full Wisp648
interface. The RJ12 and pin-header connectors are compatible with the Microchip ICD2 and
PICkit2 programmers / debuggers, but they lack the TPGM, TRDX and TTXD lines. The row of
solder pads can be used to make a permanent connection to a target, for instance when the Wisp648
is installed permanently in a system.
Kit construction
PCB
BAT85
1N5819
BC550
R 1kΩR 47Ω
DIP ICs and sockets
PCB
LED
C 22µF
C 1µF
C 470µF
C 100nF
Pin header
jumper
IC 7805 TIP122
resonator
RJ connector
Power connectors
DB15 connector
DB9 connector
Right-angle
connector

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Place and solder the three BAT85 diodes. The (black) band on the
diodes must be at the side of the white band in the PCB silkscreen
(white print on the PCB). Trim the wires.
Place and solder the four 1kΩ(brown – black – red) resistors.
Resistors are not polar, so it does not matter in which direction they
are placed, but for aesthetic purposes it makes sense to have them
all point in the same direction. Trim the wires.
Place and solder the six 47 Ω(yellow - purple – black) resistors.
Resistors are not polar, so it does not matter in which direction they
are placed, but for aesthetic purposes it makes sense to have them
all point in the same direction. Trim the wires.
Place and solder the four 1N5819 diodes. The white band on the
diodes must be at the side of the white band in the PCB silkscreen
(white print on the PCB). Trim the wires.
Place and solder the right-angle pin-header connector. For a good
connection it is recommended to solder both top and bottom sides.
Place and solder the two 100 nF capacitors. Trim the wires.
Place and solder the two PCB sockets. The sockets have a notch at
one end, which should be above the notch in the silkscreen (white
print).
Place and solder the DB9 (female) and DB15 (male) connectors.
Shifting the connectors over the PCB edge might require some
force. There is only one way the two connectors can be places with
each solder cup over a copper field on the PCB.

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Place and solder the LED. The longer wire must be put in the hole
in the middle of the silk ‘symbol’ for the LED. In other words:
insert the longer wire in the hole nearest to the DB15 connector.
Trim the wires.
Place and solder the BC550 transistor. The flat side of the transistor
must be as show: towards the resistors.
Place and solder the 20 MHz resonator. Trim the wires.
Place and solder the two-pin header.
The latest version of the PCB uses a three-pin header.
Place and solder the screw connector.
Place and solder the centre-pin power
connector. I find it convenient to bend two
of the pins before soldering.
Place and solder the one 22 µF electrolytic capacitor. The longer
wire must be inserted in the hole marked with a +. Or: all
electrolytic capacitors must have their white bands towards the
DB15 connector.
Place and solder the six 1 µF electrolytic capacitor. The longer wire
must be inserted in the hole marked with a +. Or: all electrolytic
capacitors must have their white bands towards the DB15
connector.

11
Place and solder the 7805 regulator IC. Be careful not to use the
TIP122 transistor, which has the same TO220 shape! The metal tab
of the regulator must be oriented away from the black power
connector. The metal tab corresponds to the thick wide edge on the
silkscreen drawing. I prefer to limit the component height of the
Wisp648 programmer, so I bend the regulator towards the power
connector. This requires a little slack in the wires, so it is easiest to
do this before soldering. Trim the wires.
Place and solder the TIP122 transistor. Check again that it is indeed
the transistor, not the 7805 regulator! The metal tab of the
transistor must be oriented towards the resistors. Like the regulator,
I prefer to bent the TIP122 slightly over the resistors.
Place and solder the big black RJ11/12 connector.
Place and solder the two 470 µF electrolytic capacitors. The recent
versions of the PCB have one 470 µF capacitor and one of 2200 µF,
check the PCB. The longer wire must be inserted in the hole with
the square copper pad and marked with a +. Or: all electrolytic
capacitors must have their white bands towards the DB15
connector. The capacitor nearest to the four diodes has a very tight
fit, but with some pressure I could always push it in place,
Place the two chips in their sockets. This will
be easier if you first bent the two rows of
legs a little bit towards each other. Note that
each chip has either a notch at one small side,
and/or a marking near a pin. This notch or
marking must be nearest to the edge of the
PCB.
Place the pin jumper on one pin of the pin header. The jumper
activates the TIP122 power-short option. As explained elsewhere in
this document, it is advised to have this option disabled unless you
are certain that it should be enabled.
Recent versions of the PCB have a 3-pin header. The power-short
option is activated by placing the jumper nearest to the resistors.
The power-short is disabled by removing the jumper, or (at a
request from a user who kept losing the jumper) by placing it in the
position away from the resistors. On the most recent version of the
PCB this position is marked ‘dis’, the active position is marked
‘ena’.

12
Cable
Strip a few millimeters of the six colored wires and solder them to
the female DB015 connector. The solder cups are numbered from
left to right: 1 … 8. You use only the top row, the bottom row has
only 7 cups. From left (1) to right (6) the wire colors are black, red,
green, blue, yellow and white.
Shift the six 1.6 mm diameter heat-shrink tubes over the wires and
the solder cups. The picture shows white tubes, but the color can
vary.
Apply heat to shrink the heat-shrink. The fumes from the heat-
shrink are not healthy, so do this in the open air. An electrical paint
stripper is an ideal heat source, but a cigarette lighter or even a
match could be used as alternative.
Shift the one 6.4 mm diameter heat-shrink tube over the six wires.
Bend the wires to form a bundle centered behind the connector.
Shrink this tube too.
Fasten the strain relief at the appropriate place over the wire
bundle.

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Close the hood. I prefer not to use the two locking screws because
the Wisp648 connector has no mating nuts, but feel free to use
them if you want.
Strip a few millimeters from the other ends of the wires so they can
be inserted in a solderless breadboard.
Troubleshooting
Does the LED blink?
When power is applied to the Wisp648 (either by the target circuit, via the in-circuit programming
wires, or by a wall-wart), the red LED should blink three times. When the LED does not blink you
should check
•the power supply, and
•the Wisp648 circuit around the 16F648A chip in the programmer.
Is your power OK?
If you use a wall-wart to power the Wisp648, it must supply 9..18 V DC. An AC wall-wart might
work, but only for a target circuit that uses very little current (< 100 mA). If you use the target’s
5V to power the Wisp648, make sure that it is really 5.0 V, certainly not 4.5Vor 5.5V. In either
case you must put a 100nF capacitor over the power pins of the target PIC. A larger capacitor (22
uF or more, electrolytic is OK) must also be present, not more than 20 cm (sum of ground and 5V
wire or trace lengths) away from the target PIC.
Connector pin assignments
DB9 female: RS232
Note: if you use a cable between your PC and Wisp648 it must be a straight cable (not crossed).
Pins 2, 3 and 5 (ground, receive, transmit) need to be wired, the other wires can be wired or not.
Only three pins (GND, RxD, TxD) are used by the Wisp648, the other pins are wired to provide the
usual handshake feedback.
Wisp648 is designed to work with USB-to-serial converters. The performance (the time it takes to
program a chip) might be somewhat slower than with a ‘real’ serial port, but the functionality
should not be affected. It has been tested OK with converters based on Prolific and FTDI chips. If
you find a converter that does not work with a Wisp648 I am very interested.

14
Pin name Wisp648 function
1 CD not used, but connected to 4 and 6
2 RxD Serial data: Wisp648-to-PC
3 TxD Serial data: PC-to-Wisp648
4 DTR not used, but connected to 1 and 6
5 GND Ground
6 DSR not used, but connected to 1 and 4
7 RTS not used, but connected to 8
8 CTS not used, but connected to 7
9 RTI Not used
DB15 male: connection to target
The colors correspond to the colors of the wires supplied with the kit. No wires are supplied for
pins 7 and 8, so no colors are shown for these lines.
Pin Wisp648 function
1 Ground
2 +5V
3 PGC
4 PGD
5 MCLR
6 PGM (LVP)
7 Asynch Wisp648 target
8 Asynch Wisp648 target
9..15 Not used
Black centre-pin connector and screw connector: wall-wart
The Wisp648 has two power connectors; you can use the one you prefer. The black 2.5 mm centre-
pin connector is convenient and matches the connector often found on wall-warts. The screw
connector is more reliable and should be used when a more permanent connection is to be made.
The crew connector is clearly marked ‘0’ and ‘+’. The centre-pin of the black connector must be
positive.
RJ11/12 connector: connection to target, ICD2 compatible
Pin use
1 Not connected
2 PGC
3 PGD
4 Ground
5 +5V
6 Vpp / MCLR
The RJ11/12 connector is compatible with the connector on a Microchip ICD2. Note that the
Microchip ICD2 cable reverses the pins, so the pin assignment at the target side is the mirror of the
pin assignment at the programmer side. The table shows the pin assignment at the programmer
side.
2 3 4 5
1

15
6-pin header: connection to target, PICkit2 compatible
Pin use
1 Vpp / MCLR
2 +5V
3 Ground
4 PGD
5 PGC
6 Not connected
The Wisp648 has a PICkit2 compatible pin-header connector. You can use this connector connect
to a target board that has a PICkit2-compatible pin-header connector. The table shows the use of
the pins. Pin one is the one marked with the triangle.
1 2 3 4 5

16
Connecting a target chip
●
1 8
MCLR
VCC
2 7
GND
3 6
PGC
4 5
PGD
10Fxxx chips in 8-pin DIP
●
VCC 1 8 GND
2 7 PGD
3 6 PGC
MCLR 4 5
12Fxxx chips in 8-pin DIP
●
VCC 1 14 GND
2 13 PGD
3 12 PGC
MCLR 4 11
5 10
6 9
7 8
14-pin DIP
●
VCC 1 20 GND
2 19 PGD
3 18 PGC
MCLR 4 17
5 16
6 15
7 14
8 13
9 12
10 11
20-pin DIP
●
1 28 MCLR
VCC 2 27
3 26
GND 4 25
5 24
6 23
7 22
8 21
9 20
10 19
11 18
12 17 PGD
13 16 PGC
14 15
28-pin wide DIP
●
MCLR 1 40 PGD
2 39 PGC
3 38 PGM
4 37
5 36 PGM
6 35
7 34
8 33
9 32 VCC
10 31 GND
VCC 11 30
GND 12 29
13 28
14 27
15 26
16 25
17 24
18 23
19 22
20 21
40-pin DIP
(newer PICs)
●
MCLR 1 28 PGD
2 27 PGC
3 26 PGM
4 25
5 24 PGM
6 23
7 22
GND 8 21
9 20 VCC
10 19 GND
11 18
12 17
13 16
14 15
28-pin skinny DIP
●
1 18
2 17
3 16
MCLR 4 15
GND 5 14 VCC
6 13 PGD
7 12 PGC
8 11
PGM
9 10 PGM
18-pin DIP
The pictures show how the colored wires of the Wisp648 should be connected to various target
chips. For readability the black wire is shown here as gray, and the white wire (PGM) is shown in a
box on a white background.. Note the difference in pinout between the 10F and 12F series, which
both use an 8-pin package, and between the small and wide 28-pins packages. Also note that, as far
as in-circuit programming is concerned, the 8 pin (12Fxxx only), 14 pin, and 20 pin DIP packages
are sufficiently similar to program these chips in one (20 pin) socket. The PGM pin varies between
chips, check the chips datasheet for the correct pin.

17
The FLASH versions of some older 40-pins chips, like the 16F59, use a different pinout, shown
below.
●
1 40
2 39
3 38
4 37
GND 5 38
6 35 VCC
7 34
8 33
9 32
10 31
11 30
PGC 12 29
PGD 13 28
MCLR 14 27
VCC 15 26
16 25
GND
17 24
18 23
19 22
20 21
(older PICs)
FAQ
Can Wisp648 be used with Linux
Yes, but you will have to use either the Python source version of the XWisp tool, or check whether
one of the third-party PC programs will run on your particular Linux version.
I have a Wisp628
The Wisp628 is an older version of the Wisp648. It lacked a number of hardware features that are
present on the Wisp648:
•No build-in 7805 power supply
•No build-in TIP122 circuit (could be added externally as ‘dongle’)
•No LED
•No ICD2 and PICkit2 compatible connectors
•MCLR (Vpp) was ‘forced’ to +5V (via diodes and 1k resistor)
The Wip628 used the pin 7 of the DB15 connector for the ‘dongle’ enable function. When the
dingle circuit was connected, this pin could not also be used to pass serial data from the target to
the PC. The Wisp648 firmware does drive this pin, to be compatible with Wisp628 hardware, but
its on-board ‘dongle’ circuit is connected to a different pin of the 16F648A, so it can not be
activated inadvertently by serial data.
Wisp628 board can be used with the Wisp648 firmware. It will behave as a Wisp648, except that
the hardware features that are not present on a Wisp628 will of course not work. Note that you will

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need a 16F648A chip. Recent Wisp628’s will have this chip, older Wisp628’s can have a 16F628
or 16F628A chip. The Wisp648 firmware does not fit in a 16F628 or 16F628A.
I don’t have a serial port
Wisp648 is designed to work with USB-to-serial converters. The performance (the time it takes to
program a chip) might be somewhat slower than with a ‘real’ serial port, but the functionality
should not be affected. It has been tested OK with converters based on Prolific and FTDI chips. If
you find a converter that does not work with a Wisp648 I am very interested.
I want to use a ZIF socket
Are you sure? In-circuit programming is so much easier. But assuming you know what you are
doing: you can of course connect a ZIF socket to a Wisp648. Just take care that you connect a
100nF capacitor over the power pins. And for target chips that have multiple ground and/or power
pins: connect them all. Note that the actual pins you must connect depend on the chip. Most chips
with the same number of pins use the same pins, but you might want to check the datasheet to be
sure.
Can I use a Wisp648 at 3.3V?
No, you can’t. At 3.3V the charge pump that creates the ~ 13V Vpp does not function correctly, the
MAX232 chip is out of spec, and the 16F648A can not run at 20 MHz. The Wisp648 is designed
for 5V only, if you want to program at another voltage you will need another programmer.
I want to copy one PIC chip to another PIC chip
Wisp648 and its PC software can be used to read the content of a supported PIC, save this content
into a .hex file, and write this file to another PIC chip, but only when the source PIC chip is not
read-protected. Read-protection is a feature that the author of a program can enable if he chooses to
do so. If he did, you are out of luck (and you probably have no business copying that chip). There
are companies that will read a read-protected chip for you (for some fee), so don’t rely on read-
protection as an infallible protection mechanism for your own product. But it will prevent copying
by anyone with only ‘normal’ tools.
Can I use Wisp648 for LVP programming?
No. But why would you want to? Wisp648 uses HVP programming, which can do everything that
can be done with LVP programming, plus a bit more (like changing the LVP enable fuse bit). Note
that after programming a chip, it makes no difference whether it was programmed using LVP or
HVP, except that you can not use LVP to change the LVP-enable bit in the configuration fuses.
Should I enable the power short?
(The power short is enabled by placing the jumper on pins J1.) Some PICs always require this
feature, some require it only with certain fuse settings (internal oscillator and internal MCLR),
some can’t be programmed when this feature is enabled, and some don’t care. To complicate
matters, some power supplies (especially expensive lab equipment) restart slowly after a short, so
they won’t work with this feature enabled. The most simple choice is to disable the power short,
until you need it. You will probably only need it when you program a PIC with internal MCLR
(MCLR pin configured as input pin).
Can I build my own Wisp648?
Yes you can. I explicitly allow anyone to build a Wisp648 for his own use. Of course I prefer you
to buy a kit or build Wisp648 from my webshop, but for some people even the price of the kit
might be too high. If that is the case for you: go ahead, build your own. The firmware and PC
software can be downloaded from my site. But don’t sell Wisp648 programmers, kits, PCBs or

19
programmed PICs for such programmers, and don’t build them except for your own use. Some
borderline cases:
•It is allowed to design and make a Wisp648 PCB, but it is not allowed to have it made for
you by a PCB company, nor is it allowed to sell such a PCB, or to provide the PCB design
to the general public.
•It is allowed to program a 16F648A with the Wisp648 firmware, create a PCB, or even
build a complete Wisp648 programmer for a friend, provided that it is a single programmer
(don’t start a neighborhood Wisp648 building service), and you do not make any money
doing so.
Note that there is no restriction on the use of a Wisp648 programmer. Why these restrictions at all?
Because I must make a living, and I would like my PICmicro activities to contribute to that, so I
can justify spending more time on those activities. That includes updating the Wisp648 design and
PC software for it, so in the end you will benefit too.
Can you send me the Wisp648 circuit and PCB files?
Sorry, I won't. I sell a kit containing all Wisp648 parts, including a programmed 16F648A and a
PCB. I want to encourage Do It Yourself activities, but you will have to use a breadboard, or
design your own PCB. If you want the comfort of an existing PCB: buy the kit!
Why does my Wisp648 identify itself as Wisp628?
Most PC firmware for Wisp628 checks the programmer name, and refuses to work when it is
anything but Wisp628. Wisp648 is compatible with such firmware, except that it would not work
when it revealed itself as Wisp648. So I decided to let the Wisp648 identify itself as Wisp628, at
least until all third-party PC software is modified to accept the identification ”Wisp648”.
Programming 18F fuses does not work
Some PIC fuses settings, in particular the enabling of the PLL in 18F chips, require a power-up to
take effect. Just a reset is not sufficient. By default the Wisp648 will reset the target chip after
programming, but it will not automatically cycle the power, so when you (for instance) enable the
PLL in an 18F chip for the first time you will need to remove and re-apply the power.
Your PC software sucks. I want to make my own.
No problem. But you are not the first with this idea, so you might check on the internet for third-
party PC software for the Wisp648, maybe you like it better than mine. Rob Hamerling is one
source. His website is currently at http://www.robh.nl, otherwise google will be able to find him.
But if you insist on making your own software, by all means do so. I would appreciate it if you
make your software available on the internet and drop me an email so I can mention it on the
Wisp648 page. The communication protocol used by the Wisp648 is described in other documents,
check the Wisp648 page. If these documents are not clear feel free to ask me for an explanation. Or
read the Wisp648 firmware, this too is available from the Wisp648 page.
PCB 1.05 bug
Version 1.05 of the Wisp648 PCB has a bug: the PGM line is permanently shorted to ground. The
effect is that if you use the white wire to pull the PGM/LVP pin low during programming, this pin
will permanently be pulled low, thus preventing normal use of this pin. If you don’t use this pin
you won’t notice this problem (which is why I did not discover it – thanks Johan Van Hecke!)
Now what can be done about this?
1. When you use a target chip that does not have the LVP feature you have no problem. Read
no further (at least not for now).

20
2. Instead of using the white wire you could put a pull-down resistor between the PGM/LVP
pin of your target chip and ground. A value of 10 .. 100 kΩshould work fine.
3. If your Wisp648 was bought ready-made you can contact me to have it replaced by a
corrected version.
4. You could repair the PCB. This requires cutting two traces and soldering one wire. The
pictures below show the steps. This is probably best done after the board is assembled.
Cut the two PCB traces at the
indicated places.
Now only the diagonal trace
connects to the PCB pad.
Use a short piece of wire to
connect the two pads that were
previously connected.
This is what the result should look
like.