[Raspbian-devel] Questions About the RPi Board

[Martin McCormick]

	The new RPi2 board I got does not appear to have Pin 1
marked clearly but I did find a piece of documentation on the
40-pin GPIO header. If one wants to orient the board so the pin
numbers make sense, it appears that one should turn the board
such that the USB and network ports face to your right and the
audio, HDMI and Power ports are facing you. The SD RAM slot is on
the left endtoward the board edge.

	The pins then go from left to right and the row closest
to the edge contains Pin 1 which is near the upper-left corner of
the board.

	Count by odd numbers to the right so Pin 39 is the last
pin. The second row then starts at Pin 2 and you count by even
numbers to 40.

	How did I find this out? I took a multimeter, set the
meter for continuity checking and then placed the negative probe
on the metal shield around one of the usb port
modules. Continuity showed up each time the positive probe
contacted a Ground pin and every single Ground pin listed in the
pinout matched the correct pin on the header.

	According to the pinout, there is a Ground at 6 which is
the third pin to the right of Pin 2, and it appears that one
attaches the black lead there, the white lead to Pin 8 and the
green lead to Pin 10. They are in a nice straight line on the
header.

	So far, no good. There is no serial data from the Pi
during boot even though I did remove the # to uncomment the line
in config.txt that should give one a serial console.

	Unless the serial cable or the Broadcom lines are bad,
the serial TX and RX lines are not 8 and 10. I even swapped them
once and have yet to see one character come back from the Pi.

	The really good news is that one can ssh in to the system
but one has to use the user ID of pi and use the default
password of "raspberry" to get in.

	I was lucky in that I fairly quickly found the IP address
that the Pi was assigned by the internet router so I was able to
do the setup and, except for the serial issue, everything works
as advertised.

The 32-GB SD ram card that I had DD'd the boot image on is now
configured to it's full size and set to the correct localle so
local time is right.

	I configured the WiFi adaptor to use DHCP and it works
but WiFi reception is terrible in this room soI could just barely
ssh in and had to keep squirming around to allow the little WiFi
module to talk to the router but it certainly works.

	I think I have a plan to find out whether the serial port
is actually working but it is kind of an odd approach. I could
send a steady stream of data to /dev/AMA0 and use a signal tracer
to find it on the header. The input is probably right next to it
or it is opposite it on the other row.

	I haven't played with the sound yet but this is quite an
impressive box when one considers it's cost and size. I can
imagine a number of neat projects that the Pi can do.

Martin