49 lines
1.9 KiB
Plaintext
49 lines
1.9 KiB
Plaintext
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The best source of recent information is the Arduino forum
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http://arduino.cc/forum/
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Also search the Adafruit forum
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http://forums.adafruit.com/
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If you are using a Teensy try
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http://forum.pjrc.com/forum.php
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Try running the SdInfo sketch in the SdFat/examples folder to get
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more information.
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The most common problems are:
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Wiring errors with card.init() failure and errorCode == 1. This means the
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first command, CMD0 - SPI init, failed. SdFat is not seeing the card.
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This is a basic hardware problem. Do not reformat your SD.
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card.init() failures caused by resistor SPI level shifters. Some, mostly older,
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SD cards work with resistor level shifters but may be flaky with random errors.
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Many newer SD cards have edge detectors and fail with errorCode() = 1. These
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cards will not work with resistor level shifters since SdFat does not see the
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card at low SPI clock rate.
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Other cards fail with an errorCode() > 1. These cards see SD commands at low
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SPI clock rate but fail at higher SPI clock rate. It may be possible to use
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these cards by replacing card.init() with card.init(SPI_HALF_SPEED).
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This will slow the the SPI clock by 50%.
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Redefining SS_PIN to be a pin other than the Arduino/AVR hardware SS pin.
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Arduino/AVR SPI will only function correctly in master mode if the hardware SS
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pin is in output mode. Sd2Card::init() will enable output mode for the hardware
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SS pin even if it is not SD chip select.
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If you have multiple SPI devices you must insure devices other than the SD card
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have their chip select pin high when Sd2Card::init() is called.
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If you want to understand in more detail how AVR SPI works read this
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http://www.atmel.com/dyn/resources/prod_documents/doc2585.pdf. See section 2.3.
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