Having problem with programming of PIC's. Power regulator working fine, found
problem with VDDU. Programmer ends hardware test successfully without Q2. If I
insert it back - disconnect on step 2. Q2 is working PNP transistor, no shorts
or ohmic paths in the circuit (tested by multimeter and some other devices).
There are voltages on step 1 - VDDU 4,5V, VPPU 12,43V. Disconnect happens
during switch between step 1 and step 2(power source disconnects, info lines
initiates) ONLY with Q2, Test ends normally without Q2. The PCB is new, with
brand new components (except 18F2550).
R5 - 10k 5%
R25 - 300k 5%
Voltages during test(without Q2)
VDDU - 12,3V
VPPU - 0V
RB5 - 0,5V (tested on main micro pins, without PIC in socket U3) I guess this
RB6 - 4,87V
RB7 - 4,87V
You seem to have CSS turned off.
Please don't fill out this field.
I guess we can exclude the DCDC section and concentrate on VDDU.
On hardware test step 2 VPPU goes to 0 and RB5-6-7 go high, so I would check
for possible shorts between these signals and VDDU (which happens to work fine
on step 1).
Try to monitor the current out of Q2 when you switch to test2.
I think you mean VPPU - 12,3V VDDU - 0V, but for which test? Should be test 3.
RB5 at 0,5V means that it is sinking some current, 5mA, which is not right if
there is no target chip; see if it comes from vdd directly.
What value are R26-27? Any shorts there?
Also are you using a powered hub? are there any other USB devices that sink
current from the same hub?
On step 2 VDDU goes to 0 and disconnect happens(tested on collector of Q2).
VPPU - 12,3 VDDU - 0, is without connected VDDU(Q2 is out). Yes test 3 and
RB5 measured on the main micro pins(without 100 Ohm resistor), so there is no
R26-27 is 10k 5%
I'm using onboard USB connector and I have USB mouse also. Did you mean, that
open programmer consumes more than 300 mA?
By the way ALL PCB tested for shorts more than 10 times, so I can guarantee,
that there is no short circuits.
If there is some anomalous current consumption the device will probably lose
the connection, so it's better to have a separate hub.
Try what I suggested
Nothing changed. Different computer, higher USB output(5,03V) with or without
external hub and no reaction.
By the way, voltage on the RE3 should be 4,4V or higher? I think there should
be at least 4,5... And I still have no "D" signal(RB5)...
RE3 should be at VDD level.
RB5 might be shorted, remove U2 and measure resistance to gnd.
Monitor the current through Q2 entering test 2.
Try to post a picture of your circuit, also the solder side; maybe there's
something obviously wrong.
Here it is. My PCB at this moment. A little dirty, but no shorts. RB5 is not
shorted to GND, and has no ohmic path.
I can see this is not the official pcb; I'm sure you checked all the
connections, but this is the only source of error remaining.
If you do a modification you should always use an automatic checker like it is
done with program PCB on the official source; manual/visual checks tend to
fail fairly often; is this the case?
What do you mean when saying "not official pcb"? I used your PCB from archive
on the site. This PCB is home-made variant without any modifications. I tried
to repeat your device 1 to 1. The only difference is the components (I used
And i still can't understand why there is no RB5 signal? It must be there
because 18F2550 is working. Or there is some kind of error in firmware...
It can be it will help (Quotation datasheet):
"While in Low-Voltage ICSP Programming mode, the RB5 pin can no longer be used
as a general purpose I/O pin and should be held low during normal operation".
To whip off the bit of LVP possibly only in the mode of HVP.
No, this has absolutely nothing to do with the issue; in fact I think the
problem seems to be a short on RB5: when the main micro tries to set it high a
large current flows and the USB connection is lost.
The pcb was modified manually without further checks, so I suspect there is a
wrong connection on RB5.
I'm sorry, but threre is NO MISTAKE AND NO MODIFICATIONS on the pcb! All
connections was made according to your pcb and your schematics! I repeat NO
MODIFICATONS! Short on RB5 could be only inside of main micro, but I have two
of them and this issue happens on second too... Wrong connection? I posted two
high-resolution photos, so you can check it by yourself if you don't trust me.
2 sergeyzuev: Interesting fact. It could explain this issue.
To view the high-resolution variant you should press on the picture.
I can see that the traces are curved instead of straight, but at closer look
it is like the original; this doesn't mean that there are no defects in the
pcb itself; how about a short between RB5 and some other net?
The hex provided has no LVP flag set, so RB5 is a normal IO; if you didn't
change the config word there is no problem.
Allright, let's check the programming flags. Which of them should be enabled?
To open picture - press on it.
I give up. This programmer doesn't work. And it never wouldn't work. But WHY?
I made PCB without any errors. I used components, that matches to your
circuit. I'm going to search another USB programmer...
Last question. What programmer did you used to flash the main micro(and LVP or
You are totally WRONG my friend...mine is working just fine...i can program
PIC, ATMEL and I2C EEPROM...
I used JDM based serial programmer to initially program my PIC18F2455...
JDM-based. It seems, that initial HVP programming of 18F2550 is very
necessary. My mistake is wrong programmer. I used Art-2003 and LVP-
mode(without LVP flag installed). By the way, JDM needs external 13V power
No, JDM is powered by serial port..:D
And I don't believe that it is a software issue, Since your programmer is
detected and driver was installed then it was programmed properly...
For me it's a hardware issue...btw how much voltage is develop across C1?
here is a modified ART2003 with LPV and HVP.
Already tried flashing with 2 different JDM schematics - didn't work. Let's
try yours. Could you please send me settings for LPT -port for WinPic800?
BTW all voltages, measured at OpenProgrammer testpoints is shown in the first
post of this topic.
Here is my setting for ART2003 LPT programmer..
2 kasamiko: Thanks! Great thanks! It worked! RB5 is online, no disconnects in
hardware test and no strange disconnecting when i put my arm over the socket!
Programmer works stable and I have already flashed 16F84A and second 18F2550!
Thanks everyone! By the way, you should include "HVP programming is necessary"
in the manual to avoid such kind of topics.
Thanks again! I love you guys! =)