多谢kaixingui2012 指正
第一种方法:
unsigned int val = 123456789;
send_data_uart( val & 0xff );
send_data_uart( (val >> 8) & 0xff );
send_data_uart( (val >> 16) & 0xff );
send_data_uart( (val >> 24) & 0xff );
第二种:
unsigned int val = 123456789;
unsigned char *p;
p = (unsigned char *)&val;
send_data_uart( p[0] );
send_data_uart( p[1] );
send_data_uart( p[2] );
send_data_uart( p[3] );
第一种较通用,第二种发送顺序跟大小端有关系。本回答被提问者采纳