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Thread: Oh FreHd, how thou hath thwarted me!

  1. #11
    Join Date
    Aug 2013
    Location
    Philadelphia,PA area
    Posts
    80

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    Quote Originally Posted by Hans01 View Post
    @Kevin

    If you want to solve the problem by yourself, there is a known problem with the BS170, this is what the manual says about it:
    2A. It turns out there are two different polarities for the BS170 (Q1) and the Fairchild product I used for the first 100 or so FreHDs is backwards which is why it is mounted reversed to the screen printing on the PCB. If you are building a FreHD from scratch and it gives flashing RED LED and otherwise won't work, try changing the polarity and see if that helps.
    There's another problem with Q1. As wired Q1 doesn't do anything useful. It's supposed to convert the 3.3V data from the SD Card to 5V. The gate of Q1 should be connected to 3V3 without a pullup resistor. Consult NXP Semiconductor's App Note AN10441 for details. You can also remove Q1 & R15 and jumper Q1's Source to Drain. See the attached photo. I did this on my FreHD and it works fine with my 4p. Q1-R15_mod.jpg Hope this helps.

    Tom

  2. #12

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    Hello,

    Sorry for the long delay. I actually posted awhile back, but I guess I forgot to submit it. I took Hans's advice and bought one of the TL866cs programmers, and my FreHD's now work! Wow, I thought I was losing my mind. I would highly recommend staying away from the VStager units. I think it was programming the PICs incorrectly. Interestingly, the TL866cs complained that the hex file for the FreHD was larger than the memory on the PIC, but it works anyway. Never saw that error on my other programmers. Whatever the case, I can finally move on.

    Thanks so much for everyone's help, and sorry for the delay in response. It took awhile for the new programmer to get here.

    Take care,
    -Kevin

  3. #13

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    I agree that it's probably not needed. Honestly, there are several changes I would propose making to the board, but all in all, they work fine as designed. I think the original version didn't have the FET, so there must have been a reason it was added down the road.

    As much as I've used them, I've never seen an error on a read or write.

    Thanks Tom, and take care,
    -Kevin

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