SDFAT initialisation failure

I have hardwired a couple of prototyping boards with a uSD card attached for some code development/testing. I also have an E series board with a uSD card on a standard breadboard.

I commenced testing with 3 Photons and the E series.

One of the Photons is still using firmware 0.6.2 while the other two are at 0.7.0 as is the E series.

Having had difficuly getting two of the Photons to work with SDFat examples I tested all three Photons using a single prototyping board and the same SD card.

The Photon running 0.6.2 works correctly as does the E series running 0.7.0 but the two Photons running 0.7.0 fail the cardBegin with codes 0X1, 0XFF

SInce I am using the same test harness for all three Photons must I assume that the two Photons that fail the cardBegin are faulty in some manner? SInce the E series functions correctly with 0.7.0 it is unlikely to be the effect of different firmware levels.

Thanks for any insights you can offer.

@OziGreybeard Have you tried the following:

  1. Down grading the 2 photons to 0.6.3?
  2. If not that, changing the SPI SPEED with the 2 Photons - it could be a resistance issue with the headers in your prototype board.

What pull-up resistors are there on the lines?I have found that if you want to have reliable FULL_SPEED there needs to be 100K pull-ups to 3V3. Your uSD connector is slightly different but you get the idea. Hope it helps.
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