ST AN3966 Application note

AN3966

Application note

LwIP TCP/IP stack demonstration for STM32F407/STM32F417 microcontrollers

1 Introduction

STM32F407/STM32F417 microcontrollers feature a high-quality 10/100 Mbit/s Ethernet peripheral that supports both Media Independent Interface (MII) and Reduced Media Independent Interface (RMII) to interface with the Physical Layer (PHY).

When working with an Ethernet communication interface, a TCP/IP stack is mostly used to communicate over a local or a wide area network.

This application note presents a demonstration package built on top of the LwIP (Lightweight IP) TCP/IP stack which is an open source stack intended for embedded devices.

This demonstration package contains nine applications running on top of the LwIP stack:

●Applications running in standalone mode (without an RTOS):

–A Web server

–A TFTP server

–A TCP echo client application

–A TCP echo server application

–A UDP echo client application

–A UDP echo server application

●Applications running with the FreeRTOS operating system:

–A Web server based on netconn API

–A Web server based on socket API

–A TCP/UDP echo server application based on netconn API

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Contents	AN3966

Contents

1	Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1
2	LwIP stack overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		6
	2.1	Stack features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6
	2.2	Folder organization of the LwIP stack . . . . . . . . . . . . . . . . . . . . . . . . . . . .	7
	2.3	LwIP API overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	7

2.3.1 Raw API . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.3.2 Netconn API . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.3.3 Socket API . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.4 LwIP buffer management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.4.1 Packet buffer structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.4.2 API for managing pbufs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.5 Interfacing LwIP to STM32F4x7 Ethernet network interface . . . . . . . . . . 11

3	STM32F4x7 low level driver overview . . . . . . . . . . . . . . . . . . . . . . . . . .	13
	3.1 Global Ethernet MAC/DMA functions . . . . . . . . . . . . . . . . . . . . . . . . . . . .	13

3.1.1 Ethernet MAC/DMA configuration parameters . . . . . . . . . . . . . . . . . . . . 14

3.2 DMA descriptor handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17

3.2.1 DMA descriptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.2.2 DMA descriptor handling functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

3.3 PHY control functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.4 Hardware checksum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4	Developing applications with LwIP stack . . . . . . . . . . . . . . . . . . . . . . .	22
	4.1 Developing in standalone mode using the Raw API . . . . . . . . . . . . . . . . .	22

4.1.1 Model of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 4.1.2 Example of the TCP echo server demo . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.2 Developing with an RTOS using Netconn or Socket API . . . . . . . . . . . . . 26

4.2.1 Model of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 4.2.2 Example of a TCP echoserver demo using the Netconn API . . . . . . . . 27

4.3 LwIP memory configuration options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

5

Description of the demonstration package . . . . . . . . . . . . . . . . . . . . .

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5.1 Package directories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 5.2 Demonstration settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

5.2.1 PHY interface configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 5.2.2 MAC and IP address settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 5.2.3 STM324xG-EVAL settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

6	Using the demos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	33
	6.1 Standalone demos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	33

6.1.1 Httpserver demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 6.1.2 TCP echo client demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 6.1.3 TCP echo server demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 6.1.4 UDP echo client demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 6.1.5 UDP echo server demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 6.1.6 TFTP server demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

6.2 FreeRTOS demos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

6.2.1 HTTP server netconn demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 6.2.2 HTTP server socket demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 6.2.3 UDP TCP echo server netconn demo . . . . . . . . . . . . . . . . . . . . . . . . . . 42

7	Footprint information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		43
	7.1	HTTP server demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	43
	7.2	HTTP server netconn demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	43
8	Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		45
9	Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		46

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List of tables	AN3966

List of tables

Table 1. TCP Raw API functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Table 2. UDP Raw API functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Table 3. Netconn API functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Table 4. Socket API functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Table 5. Pbuf API functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Table 6. ethernet_if.c functions description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Table 7. Global Ethernet MAC/DMA functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Table 8. MAC configuration parameters of an ETH_InitTypeDef structure. . . . . . . . . . . . . . . . . . . . 14 Table 9. DMA configuration parameters of an ETH_InitTypeDef structure. . . . . . . . . . . . . . . . . . . . 16 Table 10. DMA descriptor functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Table 11. PHY control functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Table 12. LwIP memory configuration options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Table 13. STM324xG-EVAL jumper configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Table 14. HTTP server demo footprint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Table 15. Httpserver netconn demo footprint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Table 16. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

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List of figures

Figure 1. LwIP folder organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Figure 2. Pbuf structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Figure 3. Ethernet DMA descriptor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Figure 4. Ethernet DMA descriptor chaining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Figure 5. STM32F4x7 Ethernet driver buffers and descriptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Figure 6. Tracking DMA Rx/Tx descriptors to Get/Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Figure 7. Standalone operation model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Figure 8. LwIP operation model with RTOS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Figure 9. Demonstration package structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Figure 10. Home page of the HTTP server demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Figure 11. SSI use in HTTP server demo application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Figure 12. TCP echo client demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Figure 13. TCP echo server demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Figure 14. UDP echo client demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Figure 15. UDP echo server demon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Figure 16. TFTP tool (tftpd32) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

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LwIP stack overview	AN3966

2 LwIP stack overview

2.1Stack features

LwIP is a free TCP/IP stack developed by Adam Dunkels at the Swedish Institute of Computer Science (SICS) and licensed under a modified BSD license.

The focus of the LwIP TCP/IP implementation is to reduce the RAM use while still having a full scale TCP/IP stack. This makes LwIP suitable for use in embedded systems.

LwIP comes with the following protocols:

●IPv4 and IPv6 (Internet Protocol v4 and v6)

●ICMP (Internet Control Message Protocol) for network maintenance and debugging

●IGMP (Internet Group Management Protocol) for multicast traffic management

●UDP (User Datagram Protocol)

●TCP (Transmission Control Protocol)

●DNS (Domain Name Server)

●SNMP (Simple Network Management Protocol)

●DHCP (Dynamic Host Configuration Protocol)

●PPP (Point to Point Protocol)

●ARP (Address Resolution Protocol)

LwIP has three application programming interface (API) sets:

●Raw API is the native API of LwIP. It enables the development of applications using event callbacks. This API provides the best performance and code size, but adds some complexity for application development.

●Netconn API is a high-level sequential API that requires the services of a real-time operating system (RTOS). The Netconn API enables multi-threaded operations.

●BSD Socket API: Berkeley-like Socket API (developed on top of the Netconn API)

	The source code for the LwIP stack can be downloaded at the following link:
	http://savannah.nongnu.org/projects/LwIP
Note:	This application note is based on LwIP v1.3.2

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2.2Folder organization of the LwIP stack

When unzipped, the LwIP stack files can be found under “\Utilities\Third_Party\LwIP_v1.3.2” as shown in Figure 1.

Figure 1. LwIP folder organization

●doc: documentation text files

●port/STM32F4x7: files implementing the LwIP port to STM32F4x7

–arch: STM32 architecture port files (used data types,...)

–FreeRTOS: LwIP port to STM32F4x7 using FreeRTOS

–Standalone: LwIP port to STM32F4x7 in Standalone mode

●src: source files of the LwIP stack

–api: Netconn and Socket API files

–core: LwIP core files

–include: LwIP include files

–netif: Network interface files

2.3LwIP API overview

As mentioned above, three types of APIs are offered by LwIP stack:

●Raw API

●Netconn API

●Socket API

2.3.1Raw API

The Raw API is based on the native API of LwIP. It is used to develop callback-based applications.

When initializing the application, the user needs to register callback functions to different core events (such as TCP_Sent, TCP_error,...) . The callback functions will be called from the LwIP core layer when the corresponding event occurs.

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Table 1 provides a summary of the Raw API functions for TCP applications.

	Table 1.	TCP Raw API functions
			API function	Description
			tcp_new	Creates a new TCP PCB (protocol control block).
			tcp_bind	Binds a TCP PCB to a local IP address and port.
			tcp_listen	Starts the listening process on the TCP PCB.
	TCP connection
			tcp_accept	Assigns a callback function that will be called when a
	setup
				new TCP connection arrives.
			tcp_accepted	Informs the LwIP stack that an incoming TCP
				connection has been accepted.
			tcp_connect	Connects to a remote TCP host.
			tcp_write	Queues up data to be sent.
	Sending TCP data		tcp_sent	Assigns a callback function that will be called when sent
				data is acknowledged by the remote host.
			tcp_output	Forces queued data to be sent.
			tcp_recv	Sets the callback function that will be called when new
				data arrives.
	Receiving TCP data
			tcp_recved	Must be called when the application has processed the
				incoming data packet (for TCP window management).
				Assigns a callback functions that will be called
	Application polling		tcp_poll	periodically. It can be used by the application to check if
				there is remaining application data that needs to be sent
				or if there are connections that need to be closed.
			tcp_close	Closes a TCP connection with a remote host.
	Closing and aborting			Assigns a callback function for handling connections
			tcp_err	aborted by the LwIP due to errors (such as memory
	connections			shortage errors).
			tcp_abort	Aborts a TCP connection.

Table 2 provides a summary of the Raw API functions for UDP applications.

Table 2.	UDP Raw API functions
API function		Description
udp_new		Creates a new UDP PCB.
udp_remove		Removes and de-allocates a UDP PCB.
udp_bind		Binds a UDP PCB with a local IP address and port.
udp_connect		Sets up a UDP PCB remote IP address and port.
udp_disconnect		Removes a UDP PCB remote IP and port.
udp_send		Sends UDP data.
udp_recv		Specifies a callback function which is called when a datagram is received.

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2.3.2Netconn API

The Netconn API is a high-level sequential API which has a model of execution based on the blocking open-read-write-close paradigm.

To function correctly, this API must run in a multi-threaded operation mode where there is a separate thread for the LwIP TCP/IP stack and one or multiple threads for the application.

Table 3 provides a summary of the Netconn API functions.

	Table 3.	Netconn API functions
	API function		Description
	netconn_new		Creates a new connection.
	netconn_delete		Deletes an existing connection.
	netconn_bind		Binds a connection to a local IP address and port.
	netconn_connect		Connects to a remote IP address and port.
	netconn_send		Sends data to the currently connected remote IP/port (not applicable for
			TCP connections).
	netconn_recv		Receives data from a netconn.
	netconn_listen		Sets a TCP connection into a listening mode.
	netconn_accept		Accepts an incoming connection on a listening TCP connection.
	netconn_write		Sends data on a connected TCP netconn.
	netconn_close		Closes a TCP connection without deleting it.

2.3.3Socket API

LwIP offers the standard BSD socket API. This is a sequential API which is internally built on top of the netconn.

Table 3 provides a summary of the main socket API functions.

Table 4.	Socket API functions
API function		Description
socket		Creates a new socket.
bind		Binds a socket to an IP address and port.
listen		Listens for socket connections.
connect		Connects a socket to a remote host IP address and port.
accept		Accepts a new connection on a socket.
read		Reads data from a socket.
write		Writes data on a socket.
close		Closes a socket (socket is deleted).

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2.4LwIP buffer management

2.4.1Packet buffer structure

LwIP manages packet buffers using a data structure called pbuf. The pbuf structure enables the allocation of a dynamic memory to hold a packet content and lets packets reside in the static memory.

Pbufs can be linked together in a chain. This enables packets to span over several pbufs.

Figure 2. Pbuf structure

next

payload

len

tot_len

flags ref

Room for packet headers

next pbuf structure

MS18173V

●next: pointer to next pbuf in a pbuf chain

●payload: pointer to packet data payload

●len: length of the data content of the pbuf

●tot_len: sum of pbuf len plus all the len fields of the next pbufs in the chain

●ref: (on 4 bits) reference count that indicates the number of pointers that reference the pbuf. A pbuf can be released from memory only when its reference count is zero.

●flags: (on 4 bits) indicate the type of pbuf.

LwIP defines three types of pbufs, depending on the allocation type:

●PBUF_POOL: pbuf allocation is performed from a pool of statically pre-allocated pbufs that have a predefined size. Depending on the data size that needs to be allocated, one or multiple chained pbufs are allocated.

●PBUF_RAM: pbuf is dynamically allocated in memory (one contiguous chunk of memory for the full pbuf)

●PBUF_ROM: there is no allocation for memory space for user payload, the pbuf payload pointer points to data in the ROM memory (it can be used only for sending constant data).

For packet reception, the suitable pbuf type is PBUF_POOL; it allows to rapidly allocate memory for the received packet from the pool of pbufs. Depending on the size of the received packet, one or multiple chained pbufs are allocated. The PBUF_RAM is not suitable for packet reception because dynamic allocation takes some delay. It may also lead to memory fragmentation.

For packet transmission, depending on the data to be transmitted, the user can choose the most suitable pbuf type.

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2.4.2API for managing pbufs

LwIP has a specific API for working with pbufs. This API is implemented in the pbuf.c core file.

	Table 5.	Pbuf API functions
	API function		Description
	pbuf_alloc		Allocates a new pbuf.
	pbuf_realloc		Resizes a pbuf (shrink size only).
	pbuf_ref		Increments the reference count field of a pbuf.
	pbuf_free		Decrements the pbuf reference count. If it reaches zero, the pbuf is de-
			allocated.
	pbuf_clen		Returns the count number of pbufs in a pbuf chain.
	pbuf_cat		Chains two pbufs together (but does not change the reference count of
			the tail pbuf chain).
	pbuf_chain		Chains two pbufs together (tail chain reference count is incremented).
	pbuf_dechain		Unchains the first pbuf from its succeeding pbufs in the chain.
	pbuf_copy_partial		Copies (part of) the contents of a packet buffer to an application
			supplied buffer.
	pbuf_take		Copies application supplied data into a pbuf.
	pbuf_coalesce		Creates a single pbuf out of a queue of pbufs.

Note: 1 “pbuf” can be a single pbuf or a chain of pbufs.

2When working with the Netconn API, netbufs (network buffers) are used for sending/receiving data.

3A netbuf is simply a wrapper for a pbuf structure. It can accommodate both allocated and referenced data.

4A dedicated API (implemented in file netbuf.c) is provided for managing netbufs (allocating, freeing, chaining, extracting data,...).

2.5Interfacing LwIP to STM32F4x7 Ethernet network interface

The port of LwIP stack to STM32F4x7 is located in folder “/port/STM32F4x7”.

This demonstration package provides two implementations:

●Implementation without RTOS (standalone)

●Implementation with an RTOS using FreeRTOS (http://www.freertos.org/)

For both implementations, the ethernet_if.c file is used to link the LwIP stack to the STM32F4x7 Ethernet network interface.

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Table 6 provides a summary of the ethernet_if.c functions.

Table 6. ethernet_if.c functions description

Function

Description

low_level_init

Calls the Ethernet driver functions to initialize the STM32F4x7 Ethernet peripheral.

low_level_output Calls the Ethernet driver functions to send an Ethernet packet.

low_level_input Calls the Ethernet driver functions to receive an Ethernet packet.

ethernetif_init

Calls low_level_init to initialize the Ethernet peripheral and network interface structure (netif).

ethernet_input Calls low_level_input to receive a packet and provide it to the LwIP stack.

In case of an RTOS implementation, an additional file is used (sys_arch.c). This file implements an emulation layer for the RTOS services (message passing through RTOS mailbox, semaphores,etc.). This file should be tailored according to the current RTOS, which is FreeRTOS in this package.

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3 STM32F4x7 low level driver overview

The STM32F4x7 Ethernet low level driver is located in the

\Libraries\STM32F4x7_ETH_Driver\ folder.

	The set of functions provided in the driver can be divided into the following categories:
	● Global Ethernet MAC/DMA configuration/control functions
	● DMA descriptors handling functions
	●	DMA configuration/control functions
	●	PHY control functions
	● Power Management (PMT) functions
	● MAC Management Counters (MMC) functions
3.1	Global Ethernet MAC/DMA functions
	Table 15 provides a summary of the Global Ethernet MAC/DMA functions used for the
	configuration of the media access control (MAC) and direct memory access (DMA) features.
Table 7.	Global Ethernet MAC/DMA functions
		Function	Description
ETH_DeInit			Resets the Ethernet peripheral.
ETH_StructInit			Fills a configuration structure for an Ethernet peripheral with the
			default config (see below).
ETH_Init			Initializes the Ethernet peripheral (MAC/DMA) registers with the
			required configuration.
ETH_Start			Starts the Ethernet MAC/DMA operation.
ETH_MACTransmissionCmd			Enables or disables MAC transmission.
ETH_MACReceptionCmd			Enables or disables MAC reception.
ETH_GetFlowControlBusyStatus			Checks flow control Busy flag.
ETH_InitiatePauseControlFrame			Initiates a Pause frame (full-duplex only).
ETH_BackPressureActivationCmd			Enables or disables Back pressure mechanism (half duplex mode).
ETH_GetMACFlagStatus			Gets MAC flags status.
ETH_GetMACITStatus			Gets MAC interrupts status.
ETH_MACITConfig			Configures MAC interrupts.
ETH_MACAddressConfig			Configures a MAC address.
ETH_GetMACAddress			Gets configured MAC address.
ETH_MACAddressPerfectFilterCmd			Enables or disables MAC perfect filtering for a selected MAC
			address.
ETH_MACAddressFilterConfig			Configures the MAC address filtering mode.
ETH_MACAddressMaskBytesFilterConf			Selects MAC address bytes on which filtering will be performed.
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3.1.1Ethernet MAC/DMA configuration parameters

The configuration structure for an Ethernet MAC/DMA is ETH_InitTypeDef.This structure is composed of the following MAC and DMA configuration parameters.

	Table 8.	MAC configuration parameters of an ETH_InitTypeDef structure
	Parameter		Description	Default value*
	ETH_AutoNegotiation		Enables PHY Auto-Negotiation.	ETH_AutoNegotiation_Ena
				ble
			Enables or disables Watchdog timer during
			frame reception.
	ETH_Watchdog		– When enabled, the MAC allows no more than	ETH_Watchdog_Enable
			2048 bytes to be received.
			– When disabled, the MAC can receive up to
			16384 bytes.
			– When enabled, the MAC allows no more than
	ETH_Jabber		2048 bytes to be sent.	ETH_Jabber_Enable
			– When disabled, the MAC can send up to 16384
			bytes.
	ETH_InterFrameGap		Selects the minimum IFG between frames during	ETH_InterFrameGap_96Bit
			transmission.
	ETH_CarrierSense		Enables the Carrier Sense.	ETH_CarrierSense_Enable
	ETH_Speed		Sets the Ethernet speed: 10/100 Mbps	ETH_Speed_100M
			Enables the ReceiveOwn.
	ETH_ReceiveOwn		ReceiveOwn enables the reception of frames	ETH_ReceiveOwn_Enable
			when the TX_EN signal is asserted in Half-
			Duplex mode.
	ETH_LoopbackMode		Enables the internal MAC MII Loopback mode.	ETH_LoopbackMode_Disabl
				e
	ETH_Mode		Selects the MAC duplex mode: Half-Duplex or	ETH_Mode_FullDuplex
			Full-Duplex mode
			Enables the IPv4 checksum checking for	ETH_ChecksumOffload_Dis
	ETH_ChecksumOffload		received frame payloads for TCP/UDP/ICMP
				able
			packets.
	ETH_RetryTransmission		Enables the MAC attempt retries transmission	ETH_RetryTransmission_E
			when a collision occurs (Half-Duplex mode).	nable
	ETH_AutomaticPadCRCStri		Enables the Automatic MAC Pad/CRC Stripping.	ETH_AutomaticPadCRCStri
	p			p_Disable
	ETH_BackOffLimit		Selects the BackOff limit value.	ETH_BackOffLimit_10
	ETH_DeferralCheck		Enables the deferral check function (Half-Duplex	ETH_DeferralCheck_Disab
			mode).	le
	ETH_ReceiveAll		Enables the reception of all frames by the MAC	ETH_ReceiveAll_Disable
			(No filtering).
	ETH_SourceAddrFilter		Enables Source Address Filter mode.	ETH_SourceAddrFilter_Di
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	AN3966		STM32F4x7 low level driver overview
	Table 8.	MAC configuration parameters of an ETH_InitTypeDef structure (continued)
		Parameter	Description	Default value*
	ETH_PassControlFrames		Sets the forwarding mode of the control frames	ETH_PassControlFrames_B
			(including unicast and multicast Pause frames).	lockAll
	ETH_BroadcastFramesRece		Enables the reception of Broadcast frames.	ETH_BroadcastFramesRece
	ption			ption_Disable
	ETH_DestinationAddrFilt		Sets the destination filter mode for both unicast	ETH_DestinationAddrFilt
	er		and multicast frames.	er_Normal
	ETH_PromiscuousMode		Enables Promiscuous filtering mode.	ETH_PromiscuousMode_Dis
				able
	ETH_MulticastFramesFilt		Selects the Multicast frames filter mode:	ETH_MulticastFramesFilt
			None/HashTableFilter/PerfectFilter/PerfectHashT
	er		ableFilter.	er_Perfect
			Selects the Unicast frames filter mode:	ETH_UnicastFramesFilter
	ETH_UnicastFramesFilter		HashTableFilter/PerfectFilter/PerfectHashTableFil
			ter	_Perfect
	ETH_HashTableHigh		This field holds the higher 32 bits of Hash table.	0x0
	ETH_HashTableLow		This field holds the lower 32 bits of Hash table.	0x0
	ETH_PauseTime		This field holds the value to be used in the Pause	0x0
			Time field in the transmit of a control frame.
	ETH_ZeroQuantaPause		Enables the automatic generation of Zero-	ETH_ZeroQuantaPause_Dis
			Quanta Pause control frames.	able
			Configures the threshold of the Pause to be	ETH_PauseLowThreshold_M
	ETH_PauseLowThreshold		checked for automatic retransmission of Pause
				inus4
			frame.
	ETH_UnicastPauseFrameDe		Enables the MAC detection of the Pause frames	ETH_UnicastPauseFrameDe
			(with MAC Address0 unicast address and unique
	tect		multicast address).	tect_Disable
			Enables the MAC to decode the received Pause	ETH_ReceiveFlowControl_
	ETH_ReceiveFlowControl		frame and disables its transmitter for a specified
			time (Pause Time).	Disable
	ETH_TransmitFlowControl		Enables the MAC to transmit Pause frames (Full-	ETH_TransmitFlowControl
			Duplex mode) or the MAC back-pressure	_Disable
			operation (Half-Duplex mode).
			Selects the 12-bit VLAN identifier or the	ETH_VLANTagComparison_1
	ETH_VLANTagComparison		complete 16-bit VLAN tag for comparison and
				6Bit
			filtering.
	ETH_VLANTagIdentifier		Holds the VLAN tag identifier for receive frames.	0x0
	Note:	The Default Value is the value configured by calling the ETH_StructInit function.

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