76 lines
2.1 KiB
C
76 lines
2.1 KiB
C
// Software SPI emulation
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//
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// Copyright (C) 2019 Kevin O'Connor <kevin@koconnor.net>
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//
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// This file may be distributed under the terms of the GNU GPLv3 license.
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#include "board/gpio.h" // gpio_out_setup
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#include "basecmd.h" // oid_alloc
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#include "command.h" // DECL_COMMAND
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#include "sched.h" // sched_shutdown
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#include "spicmds.h" // spidev_set_software_bus
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struct spi_software {
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struct gpio_in miso;
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struct gpio_out mosi, sclk;
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uint8_t mode;
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};
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void
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command_spi_set_software_bus(uint32_t *args)
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{
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uint8_t mode = args[4];
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if (mode > 3)
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shutdown("Invalid spi config");
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struct spidev_s *spi = spidev_oid_lookup(args[0]);
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struct spi_software *ss = alloc_chunk(sizeof(*ss));
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ss->miso = gpio_in_setup(args[1], 1);
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ss->mosi = gpio_out_setup(args[2], 0);
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ss->sclk = gpio_out_setup(args[3], 0);
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ss->mode = mode;
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spidev_set_software_bus(spi, ss);
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}
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DECL_COMMAND(command_spi_set_software_bus,
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"spi_set_software_bus oid=%c miso_pin=%u mosi_pin=%u sclk_pin=%u"
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" mode=%u rate=%u");
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void
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spi_software_prepare(struct spi_software *ss)
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{
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gpio_out_write(ss->sclk, ss->mode & 0x02);
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}
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void
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spi_software_transfer(struct spi_software *ss, uint8_t receive_data
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, uint8_t len, uint8_t *data)
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{
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while (len--) {
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uint8_t outbuf = *data;
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uint8_t inbuf = 0;
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for (uint_fast8_t i = 0; i < 8; i++) {
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if (ss->mode & 0x01) {
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// MODE 1 & 3
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gpio_out_toggle(ss->sclk);
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gpio_out_write(ss->mosi, outbuf & 0x80);
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outbuf <<= 1;
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gpio_out_toggle(ss->sclk);
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inbuf <<= 1;
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inbuf |= gpio_in_read(ss->miso);
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} else {
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// MODE 0 & 2
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gpio_out_write(ss->mosi, outbuf & 0x80);
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outbuf <<= 1;
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gpio_out_toggle(ss->sclk);
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inbuf <<= 1;
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inbuf |= gpio_in_read(ss->miso);
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gpio_out_toggle(ss->sclk);
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}
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}
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if (receive_data)
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*data = inbuf;
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data++;
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}
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}
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