/* modbus 主机实现*/

#include<stdint.h>
#include "crc.h"

// 读取保持寄存器的值
// addr  寄存器地址
// id 丛机地址
// length 读取丛机数据长度
int modbus_m_read_regist(uint8_t id,uint16_t addr,uint16_t length,uint8_t * data)
{
	uint16_t index = 0,crc;
	data[index++] = id;
	data[index++] = 0x03;
	data[index++] = (addr >> 8) & 0x00FF;
	data[index++] = addr & 0x00FF;
	data[index++] = (length >> 8) & 0x00FF;
	data[index++] = length & 0x00FF;
	crc = MX_CRC_CALC(data,index);
	data[index++] =  crc & 0x00FF;
	data[index++] = (crc >> 8) & 0x00FF;
	return index;
}


// 写入寄存器
// addr  寄存器地址
// id 丛机地址
// length 读取丛机数据长度
int modbus_m_write_regist(uint8_t id,uint16_t addr,uint16_t key,uint8_t * data)
{
	uint16_t index = 0,crc;
	data[index++] = id;
	data[index++] = 0x06;
	data[index++] = (addr >> 8) & 0x00FF;
	data[index++] = addr & 0x00FF;
	data[index++] = (key >> 8) & 0x00FF;
	data[index++] = key & 0x00FF;
	crc = MX_CRC_CALC(data,index);
	data[index++] =  crc & 0x00FF;
	data[index++] = (crc >> 8) & 0x00FF;
	return index;
}