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ce10320030
Theoretically, it works. I can access an emulated SD card on it. Will it work on real hardware? I've also made SMS emulation faster. It was unbearably slow for SDC access.
31 lines
1.0 KiB
C
31 lines
1.0 KiB
C
#include "emul.h"
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/* This emulates a SPI device being connected directly on a controller port.
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TH and TR control CLK and DI, input bit 0 (BTN_UP) is DO.
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This device has to "pulse" frequently so that it checks whether there's
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been a change in CLK.
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We have a bit of a challenge here with regards to an important limitation
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of the SMS: only 2 pins can be set as output. Without the ability to
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programatically select the SPI slave, we have to keep it selected at all
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times. This makes us vulnerable to going out of sync. This is a known
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limitation, the user will have to re-insert the SD card when that happens.
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*/
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typedef struct {
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Tristate *TH; // CLK
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Tristate *TR; // DI
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Tristate lastTH; // value of TH on last pulse
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byte bitcnt; // current xchange bit count
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bool bit; // bit to return in spi_rd()
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byte rx;
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byte tx;
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EXCH spixfn;
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} SPI;
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void spi_init(SPI *spi, Tristate *TH, Tristate *TR, EXCH spixfn);
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byte spi_rd(SPI *spi); // for sms_ports' portX_rd
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void spi_pulse(SPI *spi);
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