MAC-PHY interface using RMII not initialized (reset) on the LPC Expresso 4337 board

Discussion created by lpcware Employee on Jun 15, 2016
Content originally posted in LPCWare by vijayendar.sridharan on Mon Jan 18 08:24:47 MST 2016
Hi All,

1. I'm using the LPC Expresso board having the 4337 NXP Microcontroller with a Cortex M3 ARM core. The PHY interface has a SMSC 8720A chip.

2. When building and running the lwIP TCP echo (standalone, no RTOS) project, downloaded from LPC Expresso website, I'm unable to initialize the SMSC 8720A chip. As a result, no data is received/can be sent from/to the MAC.

3. When I try to bring it out of reset by setting the reset bit (bit 15) of the BASIC CONTROL REGISTER (index 0), I get only 0xFF as the data read from this register.

4. Data expected: Bits 15 and 11 should be zero. There's a 250 ms timeout value for this RESET to happen, but the code times out. The USE_RMII flag is enabled in the code.

5. The Yellow and Orange LEDs blink when I insert a standard Ethernet cable (CAT5/CAT3) into the RJ45 jack, I guess this rules out power supply issues.

Any ideas/suggestions on what could be wrong? Is there any jumper/mode pin I have to change on the board? Any help is greatly appreciated.

Vijayendar S