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Data storing

95.ashish

Jul 14, 2010
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Hi,
I am new to the form and i am really sorry if this kind of problem has been posted before(In that case, I would be grateful if you could redirect me to that post).

In a project that i am currently working on(university level), i would like to know the options i have to read and store data on to a memory from a timing circuit.

Consider, i am trying to build a range finder circuit. I measure the time taken for the reflected wave to reach the receiver. From this i get the distance. Now i would like to store this distance on to a memory, so that i can later use it to transfer it to a comp.

What options i got? Any places i can get help on this.

Regards,
Ashish(India)
 

NickS

Apr 6, 2010
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At first I thought you just wanted to store the data say in uC flash for later use(low complexity/cost) but at the end of your post I thought perhaps you were talking about say saving to an SD card or the like(high complexity/cost).

But their are so many options here ranging in difficulty/complexity. The two methods I have used are saving data to a EEPROM via micro controller and streaming the data off through RS232 for capture in software(used for my school project). But that does not even scratch the surface of data storage.
 

95.ashish

Jul 14, 2010
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Jul 14, 2010
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Thanks for the reply, Nick. I do not have hands on experience in this circuit building. SO what are the requisites if i am to use a EPROM? Are such circuits readily available, or do i have a design one? And what would be the approximate cost of such a circuit?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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We could tell you lots, but would it be useful or a waste of time?

Here's an analogy: I ask "I need to travel between 2 places, what do you recommend that's not too expensive?" You reply "I use auto-rickshaws". I then ask you to tell me all about them -- but I live in a snow covered area and snowshoes would be a better option, and I didn't tell you that. All the effort you go to in explaining auto-rickshaws is wasted.

So, what we really need to know first is:

1) How much data (bits, bytes, kilobytes, megabytes, gigabytes?)
2) Is timing critical (e.g. data must be written in 100nS)
3) Is it a logging application?
4) What will be doing the writing (microcontroller?)
5) What will be reading it (same uC, or do you want to have removable storage)?
6) Does it matter if data is lost if power is removed?
7) what is your power budget?
8) Do you already have any form of data or address bus (e.g. 1-wire, 8 bit bus, etc)?
 

95.ashish

Jul 14, 2010
4
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cool, point taken.

All this is for a ranging device.

1) the data is considerably small. Just the distance in metres or feet with a precision of 2 integers. So, says data in bytes.
2) Timing is not a issue. It need not necessary write data in a hurry.
3) Once I store the data, i intend to transfer it to a comp-readable device/storage.
4)" What will be doing the writing?" This option i have kept it open. Whatever does it in the simplest way, i will take that. If thats a micro controller, then it will be a microcontroller.
5) Option open again. Anything thats simple, efficient(no other constraints).
6) I am looking at a battery powered device and it doesn't matter if the data is lost. I can redo the reading.
7) Nothing specific. As mentioned, anything simple and efficient.
8) No, i don't have a specific address bus yet.

PS: I am currently pursuing engineering in Electronics and communication and this is my first time in trying to implement a circuit as this. I am comfortable with the theory aspect, the only trouble being when it comes to physically implementing the circuit.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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OK, if the storage is only a couple of bytes, then you may be able to store it in a uC itself. However I imagine that you want to store a series of these measurements?

If so, then the eeprom in some microcontrollers may be large enough. If not, then there are plenty of examples of how to interface to chips like the 24LC16B.

Since speed is not an issue, you might like to look up PicAXE data loggers in google. There are probably simpler solutions, but picaxe's are cheap to get in to, and if you're only building one or two, the slight extra expense for the chip will be easily outweighed by the lack of any need to purchase specialised programmers.

Your next issue will be how to get the data from your equipment to the uC.

I would use the inbuilt RS232 to get data out. Removable storage is an option, but it adds a lot more work (e.g. to use an SD card)
 

95.ashish

Jul 14, 2010
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Jul 14, 2010
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Thanks a lot, Steve. This surely should get me started to a great extent. Will get back if i come across any roadblocks. Thanks again.

Regards,
Ashish
 

NickS

Apr 6, 2010
367
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Thanks for the reply, Nick. I do not have hands on experience in this circuit building. SO what are the requisites if i am to use a EPROM? Are such circuits readily available, or do i have a design one? And what would be the approximate cost of such a circuit?

I want to add that if this sort of engineering is what you want to do then now is a good time for you to try laying out your first board. It seems daunting at first but it gives you better options for your projects. The schematic capture and layout software can be expensive but there are freeware packages available as well(though I have not tried them).

As for cost I used a board house that let me buy my PCB's in single quantity for cheap($33). But that deal is only for students.
 
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