1，目标板能ping通PC。
2，通过tftp下载内核时，下载一段时间后停止，不能继续下载。
send ack packet, int line 268 in tftp.c, block is 17
sending UDP to 0b01a8c0/b8:88:e3:37:f9:bb
send packet in stammc 46
packet received
packet received
Receive from protocol 0x800
recive ip packet
Got IP
len=1500, v=45
get tftp packet type data
send ack packet, int line 268 in tftp.c, block is 18
sending UDP to 0b01a8c0/b8:88:e3:37:f9:bb
send packet in stammc 46
packet received
packet received
Receive from protocol 0x800
recive ip packet
Got IP
len=1500, v=45
get tftp packet type data
send ack packet, int line 268 in tftp.c, block is 19
sending UDP to 0b01a8c0/b8:88:e3:37:f9:bb
send packet in stammc 46
packet received
packet received
Receive from protocol 0x800
recive ip packet
Got IP
len=1500, v=45
get tftp packet type data
send ack packet, int line 268 in tftp.c, block is 20
sending UDP to 0b01a8c0/b8:88:e3:37:f9:bb
send packet in stammc 46
packet received
packet received
Receive from protocol 0x800
recive ip packet
Got IP
len=1500, v=45
get tftp packet type data
send ack packet, int line 268 in tftp.c, block is 21
sending UDP to 0b01a8c0/b8:88:e3:37:f9:bb
send packet in stammc 46
packet received
packet received
Receive from protocol 0x800
recive ip packet
Got IP
len=60, v=45
packet received
packet received
Receive from protocol 0x800
recive ip packet
Got IP
len=1500, v=45
packet received
packet received
Receive from protocol 0x800
recive ip packet
Got IP
len=1500, v=45
packet received
packet received
Receive from protocol 0x800
recive ip packet
Got IP
len=1500, v=45
get tftp packet type data
Same block again; ignore it. block is 21
packet received
packet received
Receive from protocol 0x800
recive ip packet
Got IP
len=1500, v=45
packet received
packet received
Receive from protocol 0x800
recive ip packet
Got IP
len=1500, v=45
packet received
packet received
Receive from protocol 0x800
recive ip packet
Got IP
len=1500, v=45
get tftp packet type data
可以看出，在板子收到第21个包后给回复信号。但是PC机没法收到。导致整个板子没法下载。现在没法定位问题想知道这种情况我该用怎样的调试思路。是硬件的问题还是软件的问题？
