Need recommend a MCU that is to creat jpg file.

Not without a lot more data. Lkely image size is the 'obvious' extra bit of data?. Second, is how fast the conversion needs to be?. JPEG, in common with most formats of it's 'type', is harder to compress, than to decompress. You talk about collecting the data 'from a UART', but unless you are using a seriously fast data rate, if the images are any sort of size, this will take a _lot_ of time. For example, a relatively low resolution 'webcam' type image, will take 53 seconds, to send over a serial link at 57600bps. If you intend to handle colour latter, then you need to include this in your calculations at the start. What colour model is the source data in?. If (for instance), it is going to be RGB, then this will need to be converted to YCbCr, before the start of jpeg encoding. Seriously, if you need good speed, then you should probably be looking at an off the shelf hardware encoder chip, or doing the core work in a gate array, rather than using a simple processor. This will involve a lot of development work, but will give fast results. The 'cheapest' solution in terms of software development, would be to use a simple 'embedded PC', and run one of the minature Linux kernels.

Best Wishes

1) How fast do you need to do it? 2) How much raw data is there? 3) If you are using an LCD controller then why not just write the points to the screen directly and not bother messing around with compressed images?

1) I not sure, of course, as fast as good, due to it is not for real time, how about

martin

I'd be thinking about an ARM with a good bit of RAM for what you are trying to do or a dedicated codec like the one Martin suggests. If you need non-volatile storage I'd consider battery backed ram more than flash because you'll wear flash out quite quickly by decompressing to it for every picture.

If your images are a collection of single points or line drawings, jpeg is a poor choice. GIF, PNG, or one of the TIFF sub formats should work much better. Jpeg is great for photos with generally many shades of color, but poor for line art. The other formats mentioned are good at compressed storage when there are only a few colors with sharp demarcations. Unfortunately, many people misuse jpegs, especially in PDF screen dumps.

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Thad

That's 60K per page (1 bit mono), which rule out the internal memory of all 8051/PIC/AVR. So, you need to look into external memory with fast enough interface.

With what? RS232 or USB?

Do you have to save through power cycle? If not, SDRAM.

First look for a jpeg compression algorithm and find out if you can compile it for a certain MCU. I'd start looking at an MCU which can address more than 64KB.

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Reply to nico@nctdevpuntnl (punt=.)
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An ARM7 will not JPEG compress an 800 x 600 picture in 1 second. IIRC someone tried running an ARM7 at 10 MIPS and it took ~40 seconds to compress a 640 x 480 picture.

(40,000,000 us)/ 640 /480 => 130 uS / pixel at 10 MIPS or 1,3 ms/pixel at 1 MIPS. At 1 MIPS you would need 1,3 ms * 800 * 600 = 624 seconds. So you need 624 MIPS to do it in 1 second.

Maybe you can find a (significantly) better algorithm, but do not underestimate the need for performance.

A DSP is what you are looking for...

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Best Regards,
Ulf Samuelsson
This is intended to be my personal opinion which may,
or may not be shared by my employer Atmel Nordic AB