Hi Rabeeh,
On 05/04/2015 03:35 PM, Rabeeh Khoury wrote:
On 05/04/2015 07:18 AM, Nikolay Dimitrov wrote:
Hi Fabio,
On 05/04/2015 06:30 AM, Fabio Estevam wrote:
From: Fabio Estevam <fabio.este...@freescale.com>
mx6cuboxi sometimes fails to recognize the Ethernet PHY:
Net: Phy 0 not found
The explanation comes from a patch from Rabeeh:
"The LED_ACT pin on the carrier-one boards had a pull down that
forces the phy address to 0x0; where on CuBox-i and the
production HummingBoard that pin is connected directly to LED
that depending on the pull down strength of the LED it might be
sampled as '0' or '1' thus the phy address might appear as either
address 0x0 or 0x4."
There's no such thing as "LED pull-down". The forward voltage drop
of a LED is between 1.65V (red low-power LEDs) to 2.1V (green LEDs)
to even more for blue LEDs. Even the lowest Vf doesn't qualify as
logic "0" for LVCMOS33, which is around 1V max (Vil). The LED just
can't pull-down the voltage level low enough.
This is AR8035 implementation; in reset stage the LED pin is
configured as input, and pull up/down does matter. In this case it
configures the PHY address.
After reset is deasserted the same LED pin becomes output and then
according to the previous pull/up it should be active high/low (i.e.
driver or sink).
I know this. This is why I said that the pin is floating and the R+LED
can't define a proper logic level during configuration bootstrapping. In
such situations there should be an external pull-up/pull-down to make
sure things work properly.
Regards,
Nikolay
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