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// Software SPI emulation
//
// Copyright (C) 2019 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include "autoconf.h" // CONFIG_*
#include "board/gpio.h" // gpio_out_setup
#include "board/misc.h" // timer_read_time
#include "basecmd.h" // oid_alloc
#include "command.h" // DECL_COMMAND
#include "sched.h" // sched_shutdown
#include "spicmds.h" // spidev_set_software_bus
struct spi_software {
struct gpio_in miso;
struct gpio_out mosi, sclk;
uint32_t sck_ticks;
uint8_t mode;
};
void
command_spi_set_sw_bus(uint32_t *args)
{
uint8_t mode = args[4];
uint32_t pulse_ticks = args[5];
if (mode > 3)
shutdown("Invalid spi config");
struct spidev_s *spi = spidev_oid_lookup(args[0]);
struct spi_software *ss = alloc_chunk(sizeof(*ss));
ss->miso = gpio_in_setup(args[1], 1);
ss->mosi = gpio_out_setup(args[2], 0);
ss->sclk = gpio_out_setup(args[3], 0);
ss->mode = mode;
ss->sck_ticks = pulse_ticks;
spidev_set_software_bus(spi, ss);
}
DECL_COMMAND(command_spi_set_sw_bus,
"spi_set_sw_bus oid=%c miso_pin=%u mosi_pin=%u sclk_pin=%u"
" mode=%u pulse_ticks=%u");
static void
spi_delay(uint32_t end)
{
while (timer_is_before(timer_read_time(), end));
}
void
spi_software_prepare(struct spi_software *ss)
{
gpio_out_write(ss->sclk, ss->mode & 0x02);
uint32_t end = timer_read_time() + ss->sck_ticks;
spi_delay(end);
}
void
spi_software_transfer(struct spi_software *ss, uint8_t receive_data
, uint8_t len, uint8_t *data)
{
uint32_t t1 = ss->sck_ticks >> 1;
uint32_t t2 = ss->sck_ticks - t1;
uint32_t end = timer_read_time() + t1;
while (len--) {
uint8_t outbuf = *data;
uint8_t inbuf = 0;
if (ss->mode & 0x01) {
for (uint_fast8_t i = 0; i < 8; i++) {
spi_delay(end);
// MODE 1 & 3
gpio_out_toggle(ss->sclk);
gpio_out_write(ss->mosi, outbuf & 0x80);
end = timer_read_time() + t2;
outbuf <<= 1;
inbuf <<= 1;
spi_delay(end);
gpio_out_toggle(ss->sclk);
inbuf |= gpio_in_read(ss->miso);
end = timer_read_time() + t1;
}
} else {
for (uint_fast8_t i = 0; i < 8; i++) {
spi_delay(end);
// MODE 0 & 2
gpio_out_write(ss->mosi, outbuf & 0x80);
gpio_out_toggle(ss->sclk);
end = timer_read_time() + t2;
outbuf <<= 1;
inbuf <<= 1;
spi_delay(end);
inbuf |= gpio_in_read(ss->miso);
gpio_out_toggle(ss->sclk);
end = timer_read_time() + t1;
}
}
if (receive_data)
*data = inbuf;
data++;
}
}
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