ibus.c

/*
 * flysky_ibus.h
 *
 *  Created on: Feb 4, 2021
 *      Author: mokhwasomssi
 */


#include "ibus.h"


/* Static variable */
static uint8_t uart_rx_buffer[IBUS_LENGTH] = {0};
static uint8_t fail_safe_flag = 0;


/* Main Functions */
void ibus_init()
{
	HAL_UART_Receive_DMA(IBUS_UART, uart_rx_buffer, 32);
}

bool ibus_read(uint16_t* ibus_data)
{
	if(!ibus_is_valid()) 
		return false;

	if(!ibus_checksum())
		return false;

	ibus_update(ibus_data);
	return true;
}


/* Sub Functions */
bool ibus_is_valid()
{
	// is it ibus?
	return (uart_rx_buffer[0] == IBUS_LENGTH && uart_rx_buffer[1] == IBUS_COMMAND40);
}

bool ibus_checksum()
{
 	uint16_t checksum_cal = 0xffff;
	uint16_t checksum_ibus;

	for(int i = 0; i < 30; i++)
	{
		checksum_cal -= uart_rx_buffer[i];
	}

	checksum_ibus = uart_rx_buffer[31] << 8 | uart_rx_buffer[30]; // checksum value from ibus
	return (checksum_ibus == checksum_cal);
}

void ibus_update(uint16_t* ibus_data)
{
	for(int ch_index = 0, bf_index = 2; ch_index < IBUS_USER_CHANNELS; ch_index++, bf_index += 2)
	{
		ibus_data[ch_index] = uart_rx_buffer[bf_index + 1] << 8 | uart_rx_buffer[bf_index];
	}
}

/**
 * @note FS-A8S don't have fail safe feature, So make software fail-safe.
 */
void ibus_soft_failsafe(uint16_t* ibus_data, uint8_t fail_safe_max)
{	
	fail_safe_flag++;

	if(fail_safe_max > fail_safe_flag)
		return;

	// Clear ibus data
	for(int i = 0; i < IBUS_USER_CHANNELS; i++)
		ibus_data[i] = 0;

	// Clear ibus buffer
	for(int j = 0; j < IBUS_LENGTH; j++)
		uart_rx_buffer[j] = 0;

	fail_safe_flag = 0;
	return;
}

/**
 * @note This function is located in HAL_UART_RxCpltCallback.
 */
void ibus_reset_failsafe()
{
		fail_safe_flag = 0; // flag reset
}