ENC28J60 not working with 18 pin Magjack

[Kounista]

Hi everyone,

I spent the last 4 hours trying to get a response from my ENC28J60 but nothing seems to happen once i connect an ethernet cable to my magjack. I used the following schematic as a basis (it's far from being perfect, just look at how the RJ45 is connected to the NIC):

**broken link removed**

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I also would like to mention that i put a 0.1µ capacitor between each VCC and VSS pins of the ENC28J60 and that i'm using the Magjack that is illustrated in the schematic below:

**broken link removed**

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i have used pins 4,5,6 and 10,11, 12 to connect the Magjack to the ENC28J60.

When i connect an ethernet cable to the Magjack, there are no LEDs blinking, but i do have 3V3 on every Vcc pin and i have 0.886 V on the CLKOUT pin, as well as the LEDA and LEDB pins. Is it a good or a bad sign?

I have to mention that i put the /RESET to 3V3 and the /CS pin to 0V, is that correct? i also connected the magjack VC1 and VC2 pins to GND...



I'll be glad if someone could help me to know which voltages (oscillator, clkout...) i need to test in order to know if my ENC28J60 is running properly. I also would like to know if my magjack is properly connected...

It's a lot of questions, sorry! I hope you guys will be able to help me with this.


Thank you all!

 

[alexan_e]

I assume you are trying to build
I have made this circuit in a custom pcb and works fine, did you use a pcb or is wired with cables?
If you are making some other design maybe you can try to connect the parts as shown in the schematic, you can even take the avr clock from the Ethernet chip.

Alex

 

[Kounista]

Hi alexan_e,

I'm planning to use the ENC28J60 with a Fujitsu MB90543GS Micro controller, but that's another story. And you're right, that project was very helpful for me. But i'm using a slightly different Magjack with an extra six pins, so i'm not really sure it's connected to the NIC the way it should be.

Do you have an idea about voltage levels to be tested to know if the ENC28J60 is working properly?

 

[alexan_e]

No i don't know the voltages but in the CLKOUT pin you are a getting a clk, you can't really measure a voltage but the 0.8 probably indicates that the crystal is working.

rst and cs are connected correctly , reset is disabled and the chip is selected.
I'm not sure about vc1 and vc2 , should they be connected to the gnd?
In the other magjack the center tap is floating and they have a resistor/capacitor to the gnd already connected.

Alex

 

[FvM]

I don't use ENC28J60 and can't tell, if it's operational, e.g. signaling link state without configuring it through the SPI interface.

The SPI interface surely won't work with /CS tied to 3.3V (neither to GND, as done in the posted circuit). It has to be operated during SPI communication by the master.

Connecting RJ45 pin 1/2 to TX+/- and 3/6 to Rx+/- through the magnetics is correct and supposed to work. VC1/2 are apparently intended for PoE operation and won't be connected normally. Grounding them breaks the isolation provided by the transformer and is surely not recommended, but normally doing no harm.

I guess, theres rather a general problem in 28J60 operation than with the MagJack connection.

 

[alexan_e]

The SPI interface surely won't work with /CS tied to 3.3V (neither to GND, as done in the posted circuit). It has to be operated during SPI communication by the master.

That is correct, the datasheet says
The CS pin must be held low while any operation is performed and returned high when finished.

Alex

 

[Kounista]

Hi guys, thanks for your answers,

According to this project (see "Assembly and testing" section - Step two) and this thread (first answer, by "jamodio"), the ENC28J60 can be tested before being connected to any microcontroller. Apparently, when you connect an ethernet cable, and if the ENC28J60 is properly connected, one of the leds driven by the ENC should come lit indicating that there is an active ethernet link...

I tested the floowing cases but nothing seems to happens:
- /CS pin directly to GND
- /CS pin with 10k 3V3 pullup and connected to GND
- /CS pin with 10k 3V3 pullup and connected to 3V3
- /CS pin just with 10k 3V3 pullup
- /CS pin just with 10k pulldown
- /CS floating

the osc pins are delivering 1.7 volts...


But i noticed something on my Magjack and i want to know what you guys think of it:

pins 1,2,3 are connected to each other by default.
Same thing for (4,5,6), (7,8,9) and (10,11,12)

does this have something to do with the common-mode choke placement?

I'm starting to think that i bought the wrong Magjack. Datasheet can be found **broken link removed**.

 

[alexan_e]

This is the one I'm using http://shop.tuxgraphics.org/snippets/magjack-08B0-1X1T-06-F.pdf
they are quite different

Alex

---------- Post added at 17:32 ---------- Previous post was at 17:25 ----------

i found a table saying

Gigabit Single Port MagJacks, PoE (Commonly Ordered Parts)
Part Number Contacts Positions Description
0826-1X1T-80-F 8 8 10/100/1000Base-TX, Y/GO LEDs, Tab Up, PoE, Right Angle MagJack
0816-1X1T-80-F 8 8 10/100/1000Base-TX, No LEDs, Tab Up, PoE, Right Angle MagJack

mine are 10/100 i don't know what are the differences or if there is a difference in connection termination or something.

Alex

 

[FvM]

Gigabit magnetics are fine for 10/100MBit as well. The main difference is, that they connect four instead of two differential pairs.

I understand, that you have no suitable instrument to check the 28J60 operation, e.g. an oscilloscope to check the oscillator or presence of ethernet signals. There are many ways to cause circuit failure, I don't see how we could provide help much from a distance.

 

[Kounista]

Hi everyone, i hope you all spent a great weekend and thanks for your help so far,

I have tested the OSC1 pin and it's pumping out a 25 Mhz signal, so i think my ENC28J60 circuit is still ok. I'm suspecting that the magjack is still not installed correctly, do i need to connect all the differential pairs? currently i'm only connecting the (4 6 5)(Rx) and (10 11 12)(Tx) magjack pins, the rest of the pins is floating and i don't really know if they should grounded or something else..

 

[Kounista]

Hi everyone,

I just wanted to say that the magjack i was using (0826-1X1T-80) is a gigabit PoE. And after contacting the constructor's technical help i have been told that it was not designed to work with ENC28J60.

Now that i'm using a different 10/100BaseT RJ45 with integrated magnetics everything works fine.

So for those who are planning to start working with ENC28J60, avoid using the 0826-1X1T-80 part. Instead, i suggest the part that alexan_e already mentioned which is: 08B0-1X1T-06-F or you can also use 08B0-1X1T-36-F. I hope this thread will help in the future.

Thanks everyone. I'll keep this thread updated.