PSoC 5LP and microSD card - lessons learned (32GB, signal level shifting, troubleshooting et. al.)

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cross mob
Level 4
Level 4
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Hello community, to express my gratitude towards the competent assistance I received in a recent thread (see full thread here) here are a couple of learnings.

I could not post this in the original thread as it is locked for some reason now - maybe because I marked it as solved.

- Signal Level shifting problems can be addressed via the component configurator (pin properties input threshold) e.g., CMOS or LVTTL or via the CTL registers of the ports. In case you use the emFile component set the threshold of the MISO pin to LVTTL via the control register of the corresponding port. This is particularly handy when you work with microSD breakouts that have mixed signal levels e.g. inputs are level shifted but outputs are not.

- Some pins in the KIT for PSoC 5LP have hard wired capacitors which can "distort" the signals to a point where logical levels are not reached anymore. So for the SCLK signal pay attention not to use 0.2 0.3 0.4 pins as these have the bespoke capacitors.

- I did test the emFile with the above modifications and I got to read the label of the disk. Unfortunately, the result was not stable/repeatable and I did not manage to read a file or dir on the card. Pls check the original post where BiBi did a successful test. So this solution for emFile should principally work. I just don't have the time to look deeper into the situation with an oscilloscope and will work with fatFs instead.

- fatFs is slightly more flexible than emFile in that all SPI wiring is openly accessible and you can configure the pins with the IDE

- fatFS for long file names has some issues unless you use a recent version. I did deploy the latest version with my current project. It did not work out of the box so I had to apply a number of changes to the source files to make it compile and work.

- both emFile and fatFs seem to work with a 32GB microSD (sandisk) in the case of fatFs full function is quasi tested.

Thanks again to BiBi and Leo for your kind assistance.


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Hi @brandiware,

Thank you for taking time and summarizing your learnings here and for your appreciation towards the support you received.