i’m a real world EE. my company is building an IOT embedded controller that uses a W5500 and 3 out 4 of our prototypes have the same ethernet problem, which we can not resolve.
prototype number 2 works just fine.
but numbers 1, 3, and 4 all have the same problem: shortly after plugging an ethernet cable in the link led comes on (correctly) and then the active led comes on and stays on even when there is no real ethernet activity. those prototypes neither send nor do they seem to receive network traffic, although they appear to be correctly configured.
we’ve checked all four prototypes carefully using a stereo microscope and can find nothing wrong or different between them.
our PCB is based on your published reference schematics and we are using the J1B1211CCD RJ45 jack with magnetics. W5500 pins 38 thru 47 are all open (to save PCB space). we could tie them directly to VCC/GND (as appropriate) if that is considered acceptable. according to the data sheet PMODE2…0 have internal pull-ups, which is how we want the chip configured. all other W5500 pins are connected as recommended. we have tested using both 33 ohm ond zero ohm resistors for R21 thru R24 and see no dfference with respect to this problem. most of our testing has been done using zero ohm resistors; prototype number 2 has about 200 hours of successful test time with R21…24 set to zero ohms.
we have several different test programs and they seem to show that everything is ok on the spi interface - we can read and write registers with no errors.
with no cable plugged in, PHY_CFG reads as 0xBA. with a cable plugged in it reads as 0xBF.
while this is the first time that we’ve used a wizet chip, we’ve built many ethernet products using atmel and freescale processors and a variety of ethernet switch chips. those parts all have registers that we can read that help with troubleshooting, but the W5500 seems not to have any detailed status registers.
do you have any suggestions as to what might be wrong?
are there any registers that are not mentioned in the datasheet (or any pins) that might help us figure out what we’ve done wrong?
any suggestions or help would be much appreciated and we can provide you with the schematic if you so desire.