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Wojciech Zabolotny | 11 May 17:38
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[EE]: GPS logger with voice recording - Wear balancing for SD/MMC card needed?

Hi All,

I'm just working on the open source GPS logger with voice recording (to
facilitate recording tracks for the http://www.openstreetmap.org project).

The current architecture includes:
GPS module - http://www.f-tech.com.tw/datasheet/GPS/FGPMMOPA2.pdf -
first tests show, that it performs very well even at low level of GPS
signal.
CPU - Atmega32 or PIC18F4550 - not decided yet (the second one could
provide the USB access to the stored content, but Atmega32 is easier to
program...)
Slot for the SD/MMC card,
The microphone amplifier with the AGC (based on SSM2165 or similar, eg
this one:
http://www.cyfronika.com.pl/kityAVT/avt2312pdf.pdf [Polish, sorry])
UI - very limited. LED diodes or LCD display showing the quality of the
GPS signal and current operating mode. Switch ON/OFF, switch
record/pause, unstable switch - record voice annotation.
Device should be safely operable when driving a car o a bike.

The track will be stored in the NMEA format (no problem with 1GB SD/MMC
capacity).
The short voice annotations will be stored in 8-bit 8kHz PCM (also no
problem with this capacity).

The most important problem I'm facing right now is: how to store the
information on the SD/MMC card to balance the wear?
Does the internal controller perform any block readdressing to balance
the wear?
(Continue reading)

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Shawn Tan | 11 May 17:57
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Re: [EE]: GPS logger with voice recording - Wear balancing for SD/MMC card needed?

On Sunday 11 May 2008 16:40:26 Wojciech Zabolotny wrote:
> The most important problem I'm facing right now is: how to store the
> information on the SD/MMC card to balance the wear?
> Does the internal controller perform any block readdressing to balance
> the wear?

The cards these days have an extremely large number of write cycles before 
failure. And, they are fairly cheap to replace anyway. So, I wouldn't worry 
too much about write balancing.

-- 
with metta,
Shawn Tan

Aeste Works (M) Sdn Bhd - Engineering Elegance
http://www.aeste.net

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Marcel Birthelmer | 11 May 18:16

Re: [EE]: GPS logger with voice recording - Wear balancing for SD/MMC card needed?

>
> The most important problem I'm facing right now is: how to store the
> information on the SD/MMC card to balance the wear?
> Does the internal controller perform any block readdressing to balance
> the wear?
>

Wojtek,
I'm fairly certain that SD cards do their own internal wear levelling. No
need for you to worry about it.
Rgds,
- Marcel
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Brendan Gillatt | 11 May 19:11

Re: [EE]: GPS logger with voice recording - Wear balancing for SD/MMC card needed?


Wojciech Zabolotny wrote:
> Hi All,
> 
> I'm just working on the open source GPS logger with voice recording (to
> facilitate recording tracks for the http://www.openstreetmap.org project).
> 
> The current architecture includes:
> GPS module - http://www.f-tech.com.tw/datasheet/GPS/FGPMMOPA2.pdf -
> first tests show, that it performs very well even at low level of GPS
> signal.
> CPU - Atmega32 or PIC18F4550 - not decided yet (the second one could
> provide the USB access to the stored content, but Atmega32 is easier to
> program...)
> Slot for the SD/MMC card,
> The microphone amplifier with the AGC (based on SSM2165 or similar, eg
> this one:
> http://www.cyfronika.com.pl/kityAVT/avt2312pdf.pdf [Polish, sorry])
> UI - very limited. LED diodes or LCD display showing the quality of the
> GPS signal and current operating mode. Switch ON/OFF, switch
> record/pause, unstable switch - record voice annotation.
> Device should be safely operable when driving a car o a bike.
> 
> The track will be stored in the NMEA format (no problem with 1GB SD/MMC
> capacity).
> The short voice annotations will be stored in 8-bit 8kHz PCM (also no
> problem with this capacity).
> 
> The most important problem I'm facing right now is: how to store the
> information on the SD/MMC card to balance the wear?
(Continue reading)

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Dr Skip | 13 May 02:51

[EE] slave flash for digital cam

Anybody on the list do any digital photography? Has anyone put together 
interesting equipment for it? I'm interested in slave flashes right now, but 
also looking for neat, simple add-ons.

One of my digital cams is a Fuji s6000 which puts out great images and has a 
lot of really nice features, but it's only drawback is that it's got a pop-up 
flash instead of a shoe. It's handy, and some others offer both, but I'd like 
to use my external flashes.

On digitals, they often shoot a series of fast, almost invisible (to the eye) 
pre-flashes to meter before the real thing. Some solutions use a 200mS timer to 
delay the slave flash, others count and you set whatever count your cam does 
(play with the settings till it works). Typical external flashes come in low 
voltage trigger (10v I think) and high voltage (200v on one I measured, and it 
runs on 4 AA's). Triggering is by shorting the terminals.

I believe I can fashion a hood over the popup flash and drop the output. That's 
important, since I put a burn mark on a piece of paper when covering it and 
letting the cam set the power. It was amazing! A test with lens cover on and 
manual aperture or shutter and it stayed cool (low output).

It still puts out some light, but does anyone have any really simple trigger 
circuits already worked out? Maybe a phototransistor is all? Maybe a 555 timer 
on it or use a CdS cell and cap to delay it? FET or bipolar? Is there a design 
for both voltage ranges? I figure I'll make the hood, wire it to a shoe with 
this circuit, and use my flashes old-school style.

I don't want to trigger from the popup flash, since it changes the lighting. I 
have tried it with slaves with built in triggers, bouncing the popup flash to 
them and blocking it from the subject, but it still gives out of control
(Continue reading)

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