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#include <linux/module.h>
#include <linux/gpio.h>
#include <linux/hrtimer.h>
#include <linux/interrupt.h>
#include <linux/ktime.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/version.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Nuno Goncalves");
MODULE_DESCRIPTION("GL-MiFi power monitoring MCU interface");
MODULE_VERSION("0.1");
static int gpio_tx = 19;
static int gpio_rx = 8;
static int baudrate = 1200;
static int query_interval_sec = 4;
static struct hrtimer timer_tx;
static struct hrtimer timer_rx;
static ktime_t period;
static int rx_bit_index = -1;
static unsigned read_buf_ready = 0;
static unsigned read_buf_size = 0;
static char read_buf[2][64] = {{0},{0}};
static int proc_show(struct seq_file *m, void *v)
{
seq_printf(m, "%s\n", read_buf[read_buf_ready]);
return 0;
}
static int proc_open(struct inode *inode, struct file *file)
{
return single_open(file, proc_show, NULL);
}
#if LINUX_VERSION_CODE >= KERNEL_VERSION(5,6,0)
static const struct proc_ops hello_proc_ops = {
.proc_open = proc_open,
.proc_read = seq_read,
.proc_lseek = seq_lseek,
.proc_release = single_release,
};
#else
static const struct file_operations hello_proc_ops = {
.owner = THIS_MODULE,
.open = proc_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
#endif
static irq_handler_t handle_rx_start(unsigned int irq, void* device, struct pt_regs* registers)
{
if (rx_bit_index == -1)
{
hrtimer_start(&timer_rx, ktime_set(0, period / 2), HRTIMER_MODE_REL);
}
return (irq_handler_t) IRQ_HANDLED;
}
static enum hrtimer_restart handle_tx(struct hrtimer* timer)
{
ktime_t current_time = ktime_get();
const unsigned char character = 'g';
static int bit_index = -1;
// Start bit.
if (bit_index == -1)
{
gpio_set_value(gpio_tx, 0);
bit_index++;
}
// Data bits.
else if (0 <= bit_index && bit_index < 8)
{
gpio_set_value(gpio_tx, 1 & (character >> bit_index));
bit_index++;
}
// Stop bit.
else if (bit_index == 8)
{
gpio_set_value(gpio_tx, 1);
bit_index = -1;
}
hrtimer_forward(&timer_tx, current_time, bit_index == 8
? ktime_set(query_interval_sec, 0) //wait for next query cycle
: period); //wait for next bit period
return HRTIMER_RESTART;
}
void receive_character(unsigned char character)
{
if(character == '{')
read_buf_size = 0;
if(read_buf_size < (sizeof(read_buf[0])-1) || character == '}')
{
read_buf[!read_buf_ready][read_buf_size++] = character;
if(character == '}')
{
read_buf[!read_buf_ready][read_buf_size] = '\0';
read_buf_ready = !read_buf_ready;
read_buf_size = 0;
}
}
}
static enum hrtimer_restart handle_rx(struct hrtimer* timer)
{
ktime_t current_time = ktime_get();
static unsigned int character = 0;
int bit_value = gpio_get_value(gpio_rx);
enum hrtimer_restart result = HRTIMER_NORESTART;
bool must_restart_timer = false;
// Start bit.
if (rx_bit_index == -1)
{
rx_bit_index++;
character = 0;
must_restart_timer = true;
}
// Data bits.
else if (0 <= rx_bit_index && rx_bit_index < 8)
{
if (bit_value == 0)
{
character &= 0xfeff;
}
else
{
character |= 0x0100;
}
rx_bit_index++;
character >>= 1;
must_restart_timer = true;
}
// Stop bit.
else if (rx_bit_index == 8)
{
receive_character(character);
rx_bit_index = -1;
}
// Restarts the RX timer.
if (must_restart_timer)
{
hrtimer_forward(&timer_rx, current_time, period);
result = HRTIMER_RESTART;
}
return result;
}
static int __init init(void)
{
bool success = true;
proc_create("gl_mifi_mcu", 0, NULL, &hello_proc_ops);
success &= gpio_request(gpio_tx, "soft_uart_tx") == 0;
success &= gpio_direction_output(gpio_tx, 1) == 0;
success &= gpio_request(gpio_rx, "soft_uart_rx") == 0;
success &= gpio_direction_input(gpio_rx) == 0;
success &= gpio_set_debounce(gpio_rx, 1000/baudrate/2);
success &= request_irq(
gpio_to_irq(gpio_rx),
(irq_handler_t) handle_rx_start,
IRQF_TRIGGER_FALLING,
"gl_mifi_mcu_irq_handler",
NULL) == 0;
hrtimer_init(&timer_tx, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
timer_tx.function = &handle_tx;
hrtimer_init(&timer_rx, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
timer_rx.function = &handle_rx;
period = ktime_set(0, 1000000000/baudrate);
hrtimer_start(&timer_tx, period, HRTIMER_MODE_REL);
return success;
}
static void __exit exit(void)
{
disable_irq(gpio_to_irq(gpio_rx));
hrtimer_cancel(&timer_tx);
hrtimer_cancel(&timer_rx);
free_irq(gpio_to_irq(gpio_rx), NULL);
gpio_set_value(gpio_tx, 0);
gpio_free(gpio_tx);
gpio_free(gpio_rx);
remove_proc_entry("gl_mifi_mcu", NULL);
}
module_init(init);
module_exit(exit);
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