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microSD & PSoC 3 3.3V not working | Cypress Semiconductor

microSD & PSoC 3 3.3V not working

Summary: 12 Replies, Latest post by George Mois on 08 Sep 2015 06:44 AM PDT
Verified Answers: 1
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George Mois's picture
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44 posts

Hello,

  I have a problem with writing on a microSD connected directly to a PSoC 3 (CY8C3246PVI-147). It is set to work at 4MHz, and everything is OK when the PSoC is powered at 5V. However, when I power the PSoC at 3.3V, the microSD operations take a lot more time (tens of sceconds), and nothing is written on the memory card.

  Is there a problem with the PSoC outputs, not being able to command the microSD at 3.3 V power supply? If so, is a buffer chip required between the PSoC and the microSD?

  Thank you!

George

user_14586677's picture
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7648 posts

You should not need a buffer. Is there a missing pullup on the

interface ? Or one that has poor electrical connection ?

 

Whats the P/N of the SD CARD you are using ?

 

Regards, Dana.

George Mois's picture
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44 posts

Hi Dana,

 I attached a picture of the micro SD card holder's connections to the PSoC. The card I am using is a Kingston SDC4/4GB 126. When the PSoC and its I/O are powered at 5V everything works fine, although, considering the fact that the memory works at 3.6V max, this shouldn't happen. I also switched between 3 memories, thinking that it is broken.

 

Regards,

George

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user_14586677's picture
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7648 posts

You are not frying SDCARDs because you are operating them out of spec ?

Re the Vdd of 5V on the SDCARD when it is rated for 3.6 max ?

 

Regards, Dana.

George Mois's picture
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44 posts

The computer sees all the information I wrote when using 5V power supply.

Regards,

George

user_14586677's picture
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7648 posts

What may have saved the card was inability of PSOC to source high currents on interface

 

Have you looked at actual signal interface during the writes, examined timing ? Used a

logic analyzer to see the response of the card to write commands, etc, ? Checked for

severe over/undershoot on SDCARD pins.....

 

Any special power sequencing required by SDCARD ?

 

Regards, Dana.

 

 

George Mois's picture
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44 posts

Unfortunately, I have only an oscilloscope. The clock signal seems to be the same for both supply voltages. Could there be a problem with the PSoC clocks, when it is powered at 3.3? The emFile component is set to a maximum 4MHz rate. The CPU runs (I think) at 24MHz (PLL out for Bus CLK and Master Clock, IMO - 3MHz).

I don't know where to begin. Should I look for an electrical problem or in the PSoC settings?

 

Thank you,

George

George Mois's picture
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44 posts

I have some observations to add. With the max frequency in emFile set to 4MHz, at 3.3V power supply, the frequency of the SPI clock is slower (period of 2.5us). Is there a reduction of the clock performance and maximum frequency when the PSoC is powered at 3.3V. I searched the technical documents and it is not mentioned.

 

I also attach 2 images for the MOSI signal (one for 5V and one for 3.3V).

 

Regards,

George

user_14586677's picture
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7648 posts

Here is a cheap logic analyzer, I have 2 of them, work great. They advertise

24 Mhz, not sure I agree with that, but can't beat price and functionality.

 

http://www.ebay.com/itm/Compatible-With-Logic-Analyzer-USB-Cable-24M-8CH-24MHz-8Channel-ARM-FPGA-MCU-/261831462069?hash=item3cf65f0cb5

 

The clock is trimmed for frequency on startup -

 

http://www.cypress.com/documentation/application-notes/an60616-psoc-3-and-psoc-5lp-startup-procedure

 

 

 

Regards, Dana.

 

 

George Mois's picture
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44 posts

Hi Dana,

  I am sorry, I forgot 2 simple questions.

  Is 24MHz for the PLL output, bus clock and master clock, a larger value than allowable at 3.3V power supply for PSoC 3?

  What is the maximum SPI freauency at 3.3V power supply in PSoC 3 (is 4MHz not reachable in this case)?

  Thank you for the logic analyzer link! I will buy one.

 

Regards,

George

user_14586677's picture
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7648 posts

The AC specs for clocks are governed by this from datasheet -

 

11.9 Clocking
Specifications are valid for –40 °C ≤ TA ≤ 85 °C and TJ ≤ 100 °C, except where noted.

Specifications are valid for 1.71 V to 5.5 V, except where noted. Unless otherwise specified,

all charts and graphs show typical values.

 

If you look at SPI datasheet, at bottom, are AC specs, supporting 18 Mhz down to 1.71 Vddd.

 

Regards, Dana.

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