Can't ping STM32F207ZGT6U with LwIP Despite Correct Configuration
- December 8, 2025
- 2 replies
- 162 views
Issue Description:
I am unable to ping my STM32F2 board from another computer on the same network. The Ethernet link shows as UP and the MAC/IP addresses appear correctly, but ping requests timeout. I have been debugging this for a week without success.
What I’m trying to achieve:
Set up basic Ethernet communication using LwIP on STM32F2, assign a static IP (174.16.10.101), and make the board respond to ping.
Clock Configuration:
HSE: 25 MHz
PLLM: 25, PLLN: 200, PLLP: 2 → SYSCLK: 100 MHz
AHB: 100 MHz
APB1: 25 MHz
APB2: 50 MHz
ETH Clock Source: HSE (25 MHz) → RMII Ref Clock: 50 MHz
PHY: LAN8742A, Address: 0x01
What I’ve already tried (without success):
Hardware & Cabling: Verified RMII pin connections, tried multiple cables/switches.
Network Config: Static IP set correctly, firewall disabled, host PC on same subnet.
Software: No compilation errors, added etharp_gratuitous(), MAC set to 00:80:E1:AA:BB:CC.
Debug Output: Prints show interface UP, link CONNECTED, correct IP/MAC, but no ping response and no ARP entry on host.
RTOS/LwIP: CMSIS-RTOS V2, LwIP in NO_SYS mode, Ethernet thread created, MX_LWIP_Init() called in default task.
Suspected Issues:
PHY initialization/link negotiation incomplete.
Ethernet DMA/Rx descriptors not passing packets to LwIP.
Interrupts/semaphores for packet reception not triggering.
Clock/timing issue in RMII interface.
Request for Help:
Could someone please review and suggest:
Common pitfalls in LwIP + STM32F2 Ethernet setup.
How to verify if packets are actually received by the MAC.
Steps to debug PHY register states and link status.
Any known workarounds for ping/ARP issues in static IP mode.
I’ve attached relevant code snippets. Any guidance would be greatly appreciated!