1、十六进制转字符串

std::string Number2HexStr( uint32_t mData )
{
	std::stringstream ss;

	ss << std::hex << std::setw(2) << std::setfill('0') << (int)mData;

	std::string hex_str = ss.str();

	return hex_str;
}

参考链接

2、string转char[]

void String2CharArray(std::string mStr, char mSendBuf[], uint16_t mLen)
{
	for (int i = 0; i < mLen; i++)
	{
		mSendBuf[i] = mStr[i];
	}
}

参考链接

3、调用

void main()
{

	uint32_t mData = 999999u;
	std::string hex_str;
	static char sendBuf[20] = { '0' };

	hex_str = Number2HexStr(mData);
	String2CharArray(hex_str, sendBuf, hex_str.length());

	std::cout << hex_str << std::endl;

}

4、调试结果