LWIP debug output or application messages can be routed out to one of the serial ports by configuring the debug options.
Enabling debug output in LWIP
To enable debug code in LWIP, the "LWIP_DEBUG" flag needs to be defined when compiling the LWIP code. This can usually be done by using the "-D" option to define the flag as part of the argument list for the compiler. For example in the Keil tools, you can add the define C/C++ tab of the target options dialog.
To enable specific debug messages in LWIP, just set the specific define value for the LWIP *_DEBUG value to " LWIP_DBG_ON". A full list of debug defines that can be enabled can be found in the opts.h file. Just copy the defines for the debug messages you want to enable into the lwipopts.h file for your project and enable them there. A few examples are shown below.
#define TCP_DEBUG LWIP_DBG_ON #define ETHARP_DEBUG LWIP_DBG_ON #define PBUF_DEBUG LWIP_DBG_ON
Selecting debug output
The UART channel used for debug outputcan be selected by setting the UART_REDIRECT define to the UART number. On the LPC177x_8x devices, setting this to 0, 1, or 2 will enable output for UART ports 0, 1, or 2, respectively. You can completely disable output (while keep the debug code inside LWIP) by setting UART_REDIRECT to -1.
As of release v1.01, simply enabling LWIP_DEBUG as the compilation define will automatically select the right UART for debug output. You can still override the UART for output if needed, but will need to edit the UART in the debug framework file.
Caveats of enabling debug output
Enabling debug output can add significant size to the generated code based on the debug options selected for the build. It will also slow down performance of the LWIP code due to required run-time checks and output. It's is recommended to enable debug support only if needed.
Enabling just the UART for debug output adds about 4KBytes to the code size and about 512 bytes to the data size. The UART driver uses a ring buffer for buffering debug output with the UART IRQ to feed that data to the UART. The ring buffer size can be changed by changing the "UART_RING_BUFSIZE" define value in the serial.c file. Note: The call to initialize the debug framework used for LWIP debug output and printf() is active in the examples by default. Just remove the call to debug_frmwrk_init() in the examples to save some additional code and data memory. You may have also to remove the redirect.c file from the project for this change.
Enabling debug output in the LWIP code uses a varying amount of memory based on which LWIP *_DEBUG defines are enabled. Without LWIP debug output enabled and the options selected below, the code size is increased by an additional 23.5KBytes and the data size increased by 1.6KBytes.
#define LWIP_DEBUG
#define TCP_DEBUG LWIP_DBG_ON #define ETHARP_DEBUG LWIP_DBG_ON #define PBUF_DEBUG LWIP_DBG_ON #define IP_DEBUG LWIP_DBG_ON #define TCPIP_DEBUG LWIP_DBG_ON #define DHCP_DEBUG LWIP_DBG_ON #define UDP_DEBUG LWIP_DBG_ON
Note memory usage was checked at the 'default' compiler optimization setting.
Example debug output
Some example debug output use for capturing TCPIP, ethernet ARP, PBUF allocaiton and de-allocation, etc. are shown in the example output below captured from a LWIP run.
Ethernet link not yet detected, will continue Starting LWIP ping server... dhcp_start(netif=1000eddc) en0 dhcp_start(): starting new DHCP client dhcp_start(): allocated dhcpudp_bind(ipaddr = 0.0.0.0, port = 68) udp_bind: bound to 0.0.0.0, port 68 udp_connect: connected to 0.0.0.0,port 68 dhcp_start(): starting DHCP configuration dhcp_discover() pbuf_alloc(length=308) pbuf_alloc(length=308) == 200018b4 transaction id xid(abcd0001) dhcp_discover: making request dhcp_discover: realloc()ing dhcp_discover: sendto(DISCOVER, IP_ADDR_BROADCAST, DHCP_SERVER_PORT) pbuf_header: old 200018fc new 200018f4 (8) udp_send: added header in given pbuf 200018b4 udp_send: sending datagram of length 316 udp_send: UDP packet length 316 udp_send: UDP checksum 0xdee0 udp_send: ip_output_if (,,,,IP_PROTO_UDP,) pbuf_header: old 200018f4 new 200018e0 (20) ip_output_if: en0 IP header: +-------------------------------+ | 4 | 5 | 0x00 | 336 | (v, hl, tos, len) +-------------------------------+ | 0 |000| 0 | (id, flags, offset) +-------------------------------+ | 255 | 17 | 0xba9d | (ttl, proto, chksum) +-------------------------------+ | 0 | 0 | 0 | 0 | (src) +-------------------------------+ | 255 | 255 | 255 | 255 | (dest) +-------------------------------+ netif->output()pbuf_header: old 200018e0 new 200018d2 (14) etharp_send_ip: sending packet 200018b4 dhcp_discover: deleting()ing pbuf_free(200018b4) pbuf_free: deallocating 200018b4 dhcp_discover: SELECTING dhcp_discover(): set request timeout 2000 msecs tcp_bind: bind to port 7 dhcp_discover() pbuf_alloc(length=308) pbuf_alloc(length=308) == 200018b4 transaction id xid(abcd0002) dhcp_discover: making request dhcp_discover: realloc()ing dhcp_discover: sendto(DISCOVER, IP_ADDR_BROADCAST, DHCP_SERVER_PORT) pbuf_header: old 200018fc new 200018f4 (8) udp_send: added header in given pbuf 200018b4 udp_send: sending datagram of length 316 udp_send: UDP packet length 316 udp_send: UDP checksum 0xdde0 udp_send: ip_output_if (,,,,IP_PROTO_UDP,) pbuf_header: old 200018f4 new 200018e0 (20) ip_output_if: en0 IP header: +-------------------------------+ | 4 | 5 | 0x00 | 336 | (v, hl, tos, len) +-------------------------------+ | 1 |000| 0 | (id, flags, offset) +-------------------------------+ | 255 | 17 | 0xba9c | (ttl, proto, chksum) +-------------------------------+ | 0 | 0 | 0 | 0 | (src) +-------------------------------+ | 255 | 255 | 255 | 255 | (dest) +-------------------------------+ netif->output()pbuf_header: old 200018e0 new 200018d2 (14) etharp_send_ip: sending packet 200018b4 dhcp_discover: deleting()ing pbuf_free(200018b4) pbuf_free: deallocating 200018b4 dhcp_discover: SELECTING dhcp_discover(): set request timeout 2000 msecs etharp_request: sending ARP request. pbuf_alloc(length=42) pbuf_alloc(length=42) == 200018b4 etharp_raw: sending raw ARP packet. pbuf_free(200018b4) pbuf_free: deallocating 200018b4 pbuf_alloc(length=594) pbuf_alloc(length=594) == 20004cc0 ethernet_input: dest:00:60:37:12:34:56, src:00:26:f3:a2:6b:b2, type:800 pbuf_header: old 20000050 new 2000005e (-14) ip_input: iphdr->dest 0x1d0a010a netif->ip_addr 0x0 (0x0, 0x0, 0x1d0a010a) ip_input: UDP packet to DHCP client port 68 ip_input: DHCP packet accepted. ip_input: IP header: +-------------------------------+ | 4 | 5 | 0x00 | 576 | (v, hl, tos, len) +-------------------------------+ | 0 |000| 0 | (id, flags, offset) +-------------------------------+ | 64 | 17 | 0x508e | (ttl, proto, chksum) +-------------------------------+ | 10 | 1 | 10 | 1 | (src) +-------------------------------+ | 10 | 1 | 10 | 29 | (dest) +-------------------------------+ ip_input: p->len 576 p->tot_len 576 pbuf_header: old 2000005e new 20000072 (-20) udp_input: received datagram of length 556 UDP header: +-------------------------------+ | 67 | 68 | (src port, dest port) +-------------------------------+ | 556 | 0x8880 | (len, chksum) +-------------------------------+ udp (10.1.10.29, 68) <-- (10.1.10.1, 67) udp_input: calculating checksum pbuf_header: old 20000072 new 2000007a (-8) dhcp_recv(pbuf = 20004cc0) from DHCP server 10.1.10.1 port 67 pbuf->len = 548 pbuf->tot_len = 548 searching DHCP_OPTION_MESSAGE_TYPE DHCP_OFFER received in DHCP_SELECTING state dhcp_handle_offer(netif=1000eddc) en0 dhcp_handle_offer(): server 0x010a010a dhcp_handle_offer(): offer for 0x1d0a010a dhcp_select(netif=1000eddc) en0 pbuf_alloc(length=308) pbuf_alloc(length=308) == 200018b4 transaction id xid(abcd0003) pbuf_header: old 200018fc new 200018f4 (8) udp_send: added header in given pbuf 200018b4 udp_send: sending datagram of length 316 udp_send: UDP packet length 316 udp_send: UDP checksum 0x9958 udp_send: ip_output_if (,,,,IP_PROTO_UDP,) pbuf_header: old 200018f4 new 200018e0 (20) ip_output_if: en0 IP header: +-------------------------------+ | 4 | 5 | 0x00 | 336 | (v, hl, tos, len) +-------------------------------+ | 2 |000| 0 | (id, flags, offset) +-------------------------------+ | 255 | 17 | 0xba9b | (ttl, proto, chksum) +-------------------------------+ | 0 | 0 | 0 | 0 | (src) +-------------------------------+ | 255 | 255 | 255 | 255 | (dest) +-------------------------------+ netif->output()pbuf_header: old 200018e0 new 200018d2 (14) etharp_send_ip: sending packet 200018b4 pbuf_free(200018b4) pbuf_free: deallocating 200018b4 dhcp_select: REQUESTING dhcp_select(): set request timeout 2000 msecs pbuf_free(20004cc0) pbuf_free: 20004cc0 has ref 1, ending here. pbuf_free(20004cc0) pbuf_free: deallocating 20004cc0
