4550 works with fat???

Bilal · Joined: 24 Apr 2010 Posts: 75 Location: Islamabad

hi.. i am working with PIC18F4550 + mmcsd.c + fat.c + ex_fat.c
But it can be able the create any file or do anything right.
I need to know am i using the right tools??
4550 is suitable for this purpose???
My compiler is 4.093
and i have updated fat.c and mmcsd.c according to some posts i have seen in this forum.
Kindly help me regarding this.
and sorry for my English.
best wishes
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Ttelmah · Joined: 11 Mar 2010 Posts: 19253

Probably.

Big question, is how you are handling the voltage translations between the PIC, and the card?. This is the commonest source of problems. The 18F4550, operates down to 4.2v minimum, and level translators are needed between the card and the PIC.

Best Wishes

Bilal · Joined: 24 Apr 2010 Posts: 75 Location: Islamabad

I am using 3.3v for both controller and multimedia card.
Maybe I am wrong but I thought 18f4550 can perform at 3.3v.
Its datasheet said its (Wide operating voltage range) (2.0V to 5.5V).

And also mplab do program my chip on 3.3 volt. I am using PicKit3.
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Ttelmah · Joined: 11 Mar 2010 Posts: 19253

You need the _LF_ variant to run below 4.2v.
Figures 28-1, and 28-2 in the data sheet.
Maximum 18.7MHz operation at 3.3v, with the LF version.

Best Wishes

Bilal · Joined: 24 Apr 2010 Posts: 75 Location: Islamabad

Thank you very much for your help.
Actually I am using 18F4550 with 3.3V and running at 48MHz.
It works fine with other features.
Only problem with "fat".
Maybe I need controller which is made to operate on 3.3V.
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ckielstra · Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands

I don't know the Microchip production process, but very likely the 'F' and 'LF' chips are just from the same production wafer where the better chips are selected to become 'LF' types and the others 'F'. If you are creating a hobby project and your chip is running at 3.3V then you might get away with it. For professional use you don't want to take this risk as the prototype might function and then when you order 10.000 more chips you would always see them fail (Murphy's 3'rd law).

The maximum of 48MHz is too high for 3.3V. You are now overclocking the chip at both a lower voltage than specified and at a higher frequency than specified. A bad combination. At least reduce the frequency to 18.7MHz maximum.

As mentioned before, in the SD-card projects most problems come from the 3.3V SD card to 5V PIC conversion. But since your PIC is running 3.3V this isn't for you to worry about.

Other possible problems:
- What memory card are you using? The CCS drivers are getting quiet old and were designed for the original SD-cards up to 4Gb. Newer SDHC-Cards will probably fail.
- You say you can not create a file? Are you creating the file using the CCS driver or on the PC? I don't remember exactly, but there was a problem doing it one way or the other.

temtronic · Posted: Mon Sep 26, 2011 4:37 pm

If you can switch over to USB 'flash drive' modules, you could use the Vinculum modules....$35..super easy to use....

asmallri · Joined: 12 Aug 2004 Posts: 1630 Location: Perth, Australia

Bilal · Joined: 24 Apr 2010 Posts: 75 Location: Islamabad

joseph20480 · Joined: 21 Dec 2011 Posts: 42

Hi bilal !

Could you say me if you have found your bug... i try to do the same like you ... Sdcard with pic18f4550....But anything..

The compilation is ok, but any init, any file...
Thanks in advance