Port-arm archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

Re: serial console on Pi Zero W

> I'm trying to get the serial console to work on a Pi Zero W [...]

I don't know the exact hardware in question.  And I'm not competent to
check your cu command line (I use other tools for serial-line hackery).
But you do speak of a USB-to-UART bridge, which leads me to think there
is a real serial port involved somewhere.

If you're an experienced serial-line hacker, what I'm about to say will
be obvious to you, but it's not clear to me whether you are or not.

Are you certain you don't need to swap Tx and Rx?  Get them backwards
and you'll generally get silence in each direction.  Depending on
documentation to get this right is often a recipe for frustration,
since Tx and Rx switch roles depending on whether the doc author
thought of the device as DTE or DCE.

If you're not sure, I've found that two back-to-back LEDs with about a
hundred ohms of resistance in serial with them (ie: internal tie point
connected to resistor, LED A cathode, and LED B anode; one wire
connected to the other end of the resistor, the other wire connected to
the other ends of the LEDs) is a good indicator for which pin of a
serial port is being driven.  Hook it up to Tx and Rx and one of the
lights will light for the output pin but not for the input pin.
(Doesn't matter which way around you hook it up; reversing the
connections will just cause the other LED to light instead.)  You need
to ensure that each side's output is connected to the other's input.

/~\ The ASCII				  Mouse
\ / Ribbon Campaign
 X  Against HTML		mouse%rodents-montreal.org@localhost
/ \ Email!	     7D C8 61 52 5D E7 2D 39  4E F1 31 3E E8 B3 27 4B

Home | Main Index | Thread Index | Old Index