i2c_software: Implementation of software i2c (#6141)

Signed-off-by: Alan.Ma from BigTreeTech <tech@biqu3d.com>

src/i2c_software.c

@@ -0,0 +1,181 @@
+// Software I2C emulation
+//
+// Copyright (C) 2023  Kevin O'Connor <kevin@koconnor.net>
+// Copyright (C) 2023  Alan.Ma <tech@biqu3d.com>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include <string.h> // memcpy
+#include "board/gpio.h" // gpio_out_setup
+#include "board/internal.h" // gpio_peripheral
+#include "board/misc.h" // timer_read_time
+#include "basecmd.h" // oid_alloc
+#include "command.h" // DECL_COMMAND
+#include "sched.h" // sched_shutdown
+#include "i2ccmds.h" // i2cdev_set_software_bus
+
+struct i2c_software {
+    struct gpio_out scl_out, sda_out;
+    struct gpio_in scl_in, sda_in;
+    uint8_t addr;
+    unsigned int ticks;
+};
+
+void
+command_i2c_set_software_bus(uint32_t *args)
+{
+    struct i2cdev_s *i2c = i2cdev_oid_lookup(args[0]);
+    struct i2c_software *is = alloc_chunk(sizeof(*is));
+    is->ticks = 1000000 / 100 / 2; // 100KHz
+    is->addr = (args[4] & 0x7f) << 1; // address format shifted
+    is->scl_in = gpio_in_setup(args[1], 1);
+    is->scl_out = gpio_out_setup(args[1], 1);
+    is->sda_in = gpio_in_setup(args[2], 1);
+    is->sda_out = gpio_out_setup(args[2], 1);
+    i2cdev_set_software_bus(i2c, is);
+}
+DECL_COMMAND(command_i2c_set_software_bus,
+             "i2c_set_software_bus oid=%c scl_pin=%u sda_pin=%u"
+             " rate=%u address=%u");
+
+// The AVR micro-controllers require specialized timing
+#if CONFIG_MACH_AVR
+
+#define i2c_delay(ticks) (void)(ticks)
+
+#else
+
+static unsigned int
+nsecs_to_ticks(uint32_t ns)
+{
+    return timer_from_us(ns * 1000) / 1000000;
+}
+
+static void
+i2c_delay(unsigned int ticks) {
+    unsigned int t = timer_read_time() + nsecs_to_ticks(ticks);
+    while (t > timer_read_time());
+}
+
+#endif
+
+static void
+i2c_software_send_ack(struct i2c_software *is, const uint8_t ack)
+{
+    if (ack) {
+        gpio_in_reset(is->sda_in, 1);
+    } else {
+        gpio_out_reset(is->sda_out, 0);
+    }
+    i2c_delay(is->ticks);
+    gpio_in_reset(is->scl_in, 1);
+    i2c_delay(is->ticks);
+    gpio_out_reset(is->scl_out, 0);
+}
+
+static uint8_t
+i2c_software_read_ack(struct i2c_software *is)
+{
+    uint8_t nack = 0;
+    gpio_in_reset(is->sda_in, 1);
+    i2c_delay(is->ticks);
+    gpio_in_reset(is->scl_in, 1);
+    nack = gpio_in_read(is->sda_in);
+    i2c_delay(is->ticks);
+    gpio_out_reset(is->scl_out, 0);
+    gpio_in_reset(is->sda_in, 1);
+    return nack;
+}
+
+static void
+i2c_software_send_byte(struct i2c_software *is, uint8_t b)
+{
+    for (uint_fast8_t i = 0; i < 8; i++) {
+        if (b & 0x80) {
+            gpio_in_reset(is->sda_in, 1);
+        } else {
+            gpio_out_reset(is->sda_out, 0);
+        }
+        b <<= 1;
+        i2c_delay(is->ticks);
+        gpio_in_reset(is->scl_in, 1);
+        i2c_delay(is->ticks);
+        gpio_out_reset(is->scl_out, 0);
+    }
+
+    if (i2c_software_read_ack(is)) {
+        shutdown("soft_i2c NACK");
+    }
+}
+
+static uint8_t
+i2c_software_read_byte(struct i2c_software *is, uint8_t remaining)
+{
+    uint8_t b = 0;
+    gpio_in_reset(is->sda_in, 1);
+    for (uint_fast8_t i = 0; i < 8; i++) {
+        i2c_delay(is->ticks);
+        gpio_in_reset(is->scl_in, 1);
+        i2c_delay(is->ticks);
+        b <<= 1;
+        b |= gpio_in_read(is->sda_in);
+        gpio_out_reset(is->scl_out, 0);
+    }
+    gpio_in_reset(is->sda_in, 1);
+    i2c_software_send_ack(is, remaining == 0);
+    return b;
+}
+
+static void
+i2c_software_start(struct i2c_software *is, uint8_t addr)
+{
+    i2c_delay(is->ticks);
+    gpio_in_reset(is->sda_in, 1);
+    gpio_in_reset(is->scl_in, 1);
+    i2c_delay(is->ticks);
+    gpio_out_reset(is->sda_out, 0);
+    i2c_delay(is->ticks);
+    gpio_out_reset(is->scl_out, 0);
+
+    i2c_software_send_byte(is, addr);
+}
+
+static void
+i2c_software_stop(struct i2c_software *is)
+{
+    gpio_out_reset(is->sda_out, 0);
+    i2c_delay(is->ticks);
+    gpio_in_reset(is->scl_in, 1);
+    i2c_delay(is->ticks);
+    gpio_in_reset(is->sda_in, 1);
+}
+
+void
+i2c_software_write(struct i2c_software *is, uint8_t write_len, uint8_t *write)
+{
+    i2c_software_start(is, is->addr);
+    while (write_len--)
+        i2c_software_send_byte(is, *write++);
+    i2c_software_stop(is);
+}
+
+void
+i2c_software_read(struct i2c_software *is, uint8_t reg_len, uint8_t *reg
+                  , uint8_t read_len, uint8_t *read)
+{
+    uint8_t addr = is->addr | 0x01;
+
+    if (reg_len) {
+        // write the register
+        i2c_software_start(is, is->addr);
+        while(reg_len--)
+            i2c_software_send_byte(is, *reg++);
+    }
+    // start/re-start and read data
+    i2c_software_start(is, addr);
+    while(read_len--) {
+        *read = i2c_software_read_byte(is, read_len);
+        read++;
+    }
+    i2c_software_stop(is);
+}