HP 935 5.1mp digital camera. Error message: "SD card is locked".Need a cure to take pictures again.

On Tue, 14 Jun 2005 20:01:47 GMT, Steven M. Scharf wrote:

Good idea. I wonder how smart the camera's firmware is. If the switch on
the socket is stuck in "WP" mode for SD, is the firmware smart enough to
ignore this when an a MMC card is inserted, because MMC doesn't support
WP? I wouldn't count on this.

It would depend on how the software was written and what the
actual hardware problem is, but I'm not sure about switches on the
socket. It's not as if the SD card has a protuberance that pushes a
switch in the card socket. The switches are on the SD cards
themselves. They're fairly small, so many people that use SD cards
may never have noticed them.

ASAAR wrote:
On Tue, 14 Jun 2005 20:01:47 GMT, Steven M. Scharf wrote:


Good idea. I wonder how smart the camera's firmware is. If the switch on
the socket is stuck in "WP" mode for SD, is the firmware smart enough to
ignore this when an a MMC card is inserted, because MMC doesn't support
WP? I wouldn't count on this.


It would depend on how the software was written and what the
actual hardware problem is, but I'm not sure about switches on the
socket. It's not as if the SD card has a protuberance that pushes a
switch in the card socket. The switches are on the SD cards
themselves. They're fairly small, so many people that use SD cards
may never have noticed them.

The switch on the SD card doesn't do anything electrically, it's just
mechanical. The switch is on the socket; it looks at the position of the
mechanical switch on the card. It's similar to how the write protect on
cassette tapes work (though these are breakaway tabs that cannot be
undone, except with a piece of tape).

On Wed, 15 Jun 2005 09:38:45 GMT, Steven M. Scharf wrote:

Good idea. I wonder how smart the camera's firmware is. If the switch on
the socket is stuck in "WP" mode for SD, is the firmware smart enough to
ignore this when an a MMC card is inserted, because MMC doesn't support
WP? I wouldn't count on this.

It would depend on how the software was written and what the
actual hardware problem is, but I'm not sure about switches on the
socket. It's not as if the SD card has a protuberance that pushes a
switch in the card socket. The switches are on the SD cards
themselves. They're fairly small, so many people that use SD cards
may never have noticed them.

The switch on the SD card doesn't do anything electrically, it's just
mechanical. The switch is on the socket; it looks at the position of the
mechanical switch on the card. It's similar to how the write protect on
cassette tapes work (though these are breakaway tabs that cannot be
undone, except with a piece of tape).

Well, I was right about there not being a switch-activating
protuberance on the card, and you appear to be right that the real
switch is in the socket. Looking at an SD socket in a PDA it
appears that when either an MMC or SD card is inserted, a mechanical
part in the socket tries to move into an opening in the card, which
would either be uncovered by moving the switch on an SD card into
its 'write-protect' position, or which doesn't exist at all in MMC
cards. So the good news is that the switch in the socket can't be
stuck in the 'WP-enabled' position, as that would prevent the card
from being inserted, and if it was stuck in any position, it would
be in the 'WP-disabled' position. But that simply indicates that
what's broken isn't the mechanical plunger part of the switch in the
socket. Even if some crud found its way into the socket and jammed
the switch, preventing the plunger from moving, that would only
(falsely) indicate a 'WP-disabled' condition. It might be that
another part of the switch failed, or the failure is somewhere else
in the camera, and if that's the case, even MMC cards might appear
to be Write-Protected. But if an MMC card could be found, it would
still be worth trying, but I now agree with your conclusion that
success shouldn't be counted on.

ASAAR wrote:

But that simply indicates that
what's broken isn't the mechanical plunger part of the switch in the
socket. Even if some crud found its way into the socket and jammed
the switch, preventing the plunger from moving, that would only
(falsely) indicate a 'WP-disabled' condition.

Not necessarily. It depends on whether the switch in the socket is
normally closed with no WP, or normally open with no WP.

Usually these set-ups will have an input to the microcontrolled pulled
high with a resistor, and the switch closing will connect the signal to
ground (active low). There could be a piece of solder, or other fragment
of metal stuck between the contacts of the switch, etc. It's a hokey
arrangement. They should have used optical sensing, but this is more
expensive than a mechanical switch.

One more reason to stick with Compact Flash.

On Wed, 15 Jun 2005 17:16:47 GMT, Steven M. Scharf wrote:

But that simply indicates that
what's broken isn't the mechanical plunger part of the switch in the
socket. Even if some crud found its way into the socket and jammed
the switch, preventing the plunger from moving, that would only
(falsely) indicate a 'WP-disabled' condition.

Not necessarily. It depends on whether the switch in the socket is
normally closed with no WP, or normally open with no WP.

No, I think you're missing the point. It doesn't matter whether
the switch is normally closed or open. Either way, the mechanical
plunger part isn't causing the problem, which was the point. If a
normally closed switch indicates 'WP-disabled" but a piece of dirt
prevents the switch's contacts from touching, the card would appear
to be write-protected. Similarly, if a normally open switch
indicates 'WP-disabled' but something broke inside that switch that
prevented the switch from opening, it would also indicate a
write-protected card. In fact, it doesn't have to be a problem with
the switch at all. A bad solder joint, or some conductive crud on
the PCB could cause the problem too.

I see that your next point matches what I just got through saying,
so I guess we're pretty much in agreement.


One more reason to stick with Compact Flash.

Because CF sockets don't have switches? They can have other
problems, and I've seen a couple of people that claim to have had
serious problems due to accidentally bending pins. Some people
prefer CF cards because they're physically large. Others dislike
them for the same reason. Card types don't matter very much to me,
although I'd go out of my way to avoid using MMC and MS cards. More
important to me is that the camera be able to use standard AA (or
AAA) cells. Other people prefer Li-ion rechargeables. Even better
are devices (and I know a few) that let you use either type.

Steven M. Scharf wrote:
ASAAR wrote:

But that simply indicates that
what's broken isn't the mechanical plunger part of the switch in the
socket. Even if some crud found its way into the socket and jammed
the switch, preventing the plunger from moving, that would only
(falsely) indicate a 'WP-disabled' condition.


Not necessarily. It depends on whether the switch in the socket is
normally closed with no WP, or normally open with no WP.

Usually these set-ups will have an input to the microcontrolled pulled
high with a resistor, and the switch closing will connect the signal to
ground (active low). There could be a piece of solder, or other fragment
of metal stuck between the contacts of the switch, etc. It's a hokey
arrangement. They should have used optical sensing, but this is more
expensive than a mechanical switch.

One more reason to stick with Compact Flash.


Looking at pictures of the cards, SD and MMC it looks as if the MMC has
no detail where the SD has the wp switch, so the camera needs its switch
depressed to enable write. Looking inside my usb card reader, this seems
to have a simple contact arrangement, leading to the thought that
contact closed = write enable. So you have either as suggested elsewhere
a camera circuit board fault, dirty contacts, or a card and switch that
are too close to the limit of operating tolerance. Have you tried adding
a couple of layers of tape to the side of the card to press the switch a
bit harder? If that works you could build up a card with glue just for
this camera and forget about the write protect feature