topic Re: SDHC card MISO Remains Low in ColdFire/68K Microcontrollers and Processors

SDHC card MISO Remains Low

Dave_W — Fri, 16 Sep 2011 20:25:13 GMT

I'm having an issue communicating with my SDHC card. I should mention that I have communicated with this card before with the same code on a slightly older version of the circuit.

The mcf51 is communicating with the card via SPI via potential dividers on CS, MOSI and SCK as the micro is running at 5V to fulfill several other requirements. The MISO line is put through a hex inverter to buffer the signal up to 5V.

I have not connected any pullup resistors anywhere, but I assumed that it wasn't necessary given that first prototype I made worked without them with this same card.

Essentially I get no response from the card. The MISO line remains Low all the time. Can anyone suggest a potential reason for this?

Thanks in advance

Dave Wright

Re: SDHC card MISO Remains Low

FridgeFreezer — Mon, 19 Sep 2011 19:14:38 GMT

So it was working, then you changed the circuit and it doesn't work anymore. I think there's a clue there

What does the electrical specification say for each of the devices you're using?

Re: SDHC card MISO Remains Low

Dave_W — Mon, 19 Sep 2011 19:33:24 GMT

It was not quite as 2 dimensional as that, there were no changes in the electrical schematic only in the PCB layout so there should have been no hardware induced issues.

I was hoping there was a common problem that caused a low MISO but I couldn't find anything on forums.

However I solved the issue, it came down to a poor contact that was hidden under the smd sd socket. It wasn't immediately clear even with a microscope.

Thanks for the response.