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Topic: Inserting SD card causes a reboot? (Read 644 times) previous topic - next topic

mprowe

Hi,

I think that this is a hardware question? So here goes:

The attached is a schematic for a data logger that I have built. In (most) cases it works as I would wish.
However (isn't there always!), when I insert my micro SD card, the ATMega reboots. Not what I would wish.
My first thoughts were Brownout? As the supply voltage drops as the card is powered up. Scoping the supplies (3v3 & 5v) shows no problems that I can detect. And bunging in larger & larger capacitors on the supply line have no effect.
I also understand that the SD Cards IO are tri-state until CS is activated and I can't see any disturbance on them as I insert the card..

I read various comments on the requirement for pull-up resistors on the control lines but I think the consensus is "Not needed". I also see designs with HC4050's as level shifters  But this design is all 3v3 (except for the I2C display). 

Any thoughts or comment will be most welcome.

Regards, Martin

knut_ny

Quote
I also understand that the SD Cards IO are tri-state until CS is activated
This may not be true. ..
Try 'insert card' routine with MO/MI disconnected
Ny

jendalinda

Try some buffer chip. 74HC125, 74HC244, 74HC245 etc.

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