mirror of https://github.com/hsoft/collapseos.git
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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