2020-10-31 11:31:47 +11:00
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# Accessing SD cards
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SD cards support the SPI protocol. If you have a SPI relay
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(doc/hw/spi.txt) and a driver for it that implement the SPI
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protocol (doc/protocol.txt), you're a few steps away from
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accessing SD cards!
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What you need to do is to add the SDC subsystem to your Collapse
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OS binary. First, define SDC_DEVID to a mask selecting the
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proper device on your SPI relay (this is what is sent to
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"(spie)"). For example, a SDC_DEVID or 1, 2, 4, or 8 would
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select SPI device 1, 2, 3 or 4.
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The subsystem is loaded with "423 436 LOADR".
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Initialization of the SDC system is done in multiple steps.
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First, the BLK system needs to be initialized with "BLK$". Then
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2021-01-03 07:51:12 +11:00
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you can plug SDC@ and SDC! into BLK with "' SDC@ ' BLK@* **!"
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and "' SDC! ' BLK! **!". That only needs to be done once per
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boot.
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2020-10-31 11:31:47 +11:00
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Then, the SD card that was inserted needs to be initialized. You
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can do it with "SDC$". If you have no error, it means that the
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system can spek to your card, that sync is fine, etc. You can
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read/write right now. SDC$ needs to run every time a new card
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is inserted.
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Collapse OS' SDC drivers are designed to read from the very
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first 512 sector of the card, mapping them to blocks
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sequentially, 2 sectors per block.
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