STM32 based LXI Device using Ethernet, LwIP, httpd, SCPI

• stm32f746zg (Nucleo)
• STM32CubeIDE

• ✅ DHCP IP Address Management
  • MCU continues to run even without active Ethernet connection
  • MCU connects to Network when pluged in via Ethernet
• ✅ http web interface
  • ✅ has switches to turn on/off configurations
  • ✅ uses CGI/SSI
  • ⚠️ mandatory /lxi/identification.xml is present (but not detected by the LXI tool)
• ✅ custom physical MAC address from within firmware
  • ✅ unique EUI48 address is read from EEPROM
• ✅ EEPROM to save/load user settings (IP, DHCP config ...)
• ✅ Settings allow to enable/disable DHCP + AutoIP or manual settings (IP/Netmask/Gateway)

• How to make Ethernet and lwIP working on STM32
• Tutorial HTTPd web-server on STM32 with SSI
• STM32F7 LwIP_TCP_Echo_Server
• STM32H7 LwIP_UDP_Echo_Server
• SCPI parser Library
• List of LXI Ports & Protocols
• UDP/Portmap Identification Broadcast example packet: liblxi
• Correct SSI API application: ssi_example.c

• official LXI Discovery Tool
  • This sends out a UDP/RPC/Portmap broadcast with the GETPORT command
  • the LXI device must reply to this broadcast in rcp_server.c
  • Then the tool requests the http://<host>/lxi/identification.xml from the device
• lxi-tools
  • This sends out a UDP/RPC/Portmap broadcast with the GETPORT command
  • according to wireshark, the device does not reply --> how does it work then?
  • The tool will attempt to connect to the device via VXI-11 and *IRQ? the name
• Wireshark

• ⚠️ [Bug] stops at: queue.c:1429 configASSERT(pxQueue->uxItemSize == 0)
  • https://community.st.com/s/question/0D50X0000BJ1iquSQB/bug-in-cubemx-ide-lwip-freertos-on-nucleo-f429zi
• 🔄 [Feature] make dynamic version of /lxi/identification.xml with appropriate SSI implementation
  • https://www.nongnu.org/lwip/2_0_x/group__httpd.html
  • (?) reverse changes in httpd.c because SSI can be controlled by makefsdata
  • (?) since the xml file contains <!--comments--> the LXI Discovery tool does not recognize the device anymore
  • ⚠️ LXI Identification still unclear, lxi-tools vs. LXI Identification Tool do not behave the same
  • Assertion "sys_timeout: timeout != NULL, pool MEMP_SYS_TIMEOUT is empty" failed at line 190 in ../Middlewares/Third_Party/LwIP/src/core/timeouts.c

• ❌ [Feature] function to check web connection status
  • or callback handlers when connected / disconnected
• ❌ [reliability] Add further ASSERT() statements throughout the code (e.g. for SSI)
• ❌ [refactor] author/licence/description header for each file
• 🔄 [refactor] cleanup spaghetti code of global variables, introduce hierarchy of config headers
• ❌ [refactor] implement clear MVC structure for SCPI commands
• ❌ [Feature] add hislip compatibility
• ❌ [refactor] refactor/rename scpi_server.c to tcp/ip (does this have a name? VXI?)
• ❌ [reliability] use MUTEX for UART ringbuffer?
• ❌ [reliability] implement a memory monitor (FreeRTOS?) to check on heap/stack/RAM usage
• ❌ [refactor] use SCPI_Result**** API as return throughout scpi User Code
• ❌ [Feature] enable https within lwip
• ❌ [Feature] enable web login
  • probably not supported by LwIP, requires form post and session creation using a cookie in the post header
  • password is stored on EEPROM
  • redesign of web interface is required

• exclude from build:
  • fs_data.c
  • fs_data_custom.c

• lwip/ip4_addr.h parse and verify IPv4 addresses (documentation)

• scpi/parser.h parse and extract parameters from ascii (documentation)

• Webinterface (http / port 80)
  • http://192.168.1.179/
  • http://192.168.1.179/lxi/identification

Core/Src and Core/Inc

• scpi-def.c
  • SCPI commands definition
  • SCPI command callback functions
  • command parsing, argument preprocessing + sanitization
• stm32f7xx_it.c
  • USART Interrupt for UART SCPI
• http_cgi_app.c
  • CGI + SSI implementation for the httpd Webserver
  • SSI works for both the Website and the identification.xml
• rpc_server.c
  • implements the Sun-RPC Protocol based on UDP (more specifically the Portmap protocol)
  • When a UDP Broadcast (IP address: xxx.xxx.xxx.255) is received, the LXI device must answer correctly

Tools/fs

• Filesystem for the Webserver
• use any program makefsdata (perl, C, ...) to convert the file System to a C source file fs_data_custom.c
• fs_data_custom.c must be copied to ./Middlewares/Third_Party/LwIP/src/apps/http after re-generation

LWIP/App

• lwip.c
  • initialization with DHCP
  • initialization with manual IP

LWIP/Target

• LWIP/Target/ethernetif.c contains some User Code to set the PHY/MAC address

• eeprom_24aa.h contains macros to store and retreive data (e.g. manual IP config) in EEPROM

#define LWIP_HTTPD_MAX_TAG_NAME_LEN 8 #define LWIP_HTTPD_MAX_TAG_INSERT_LEN 192