A20 does not seem to boot, no hdmi output, can't see it in network

[daniel_]

Hi there,

I am trying to get my A20 (without NAND) working. I tried the latest official Debian Image -> When plugging in the Power Cord both the red and the green light turn on. On HDMI nothing happens. Tried 2 cables. Tried with and without Ethernet cable/Keyboard/mouse. Always the same. I use a 16gig Samsung mSDCard.

Then I tried the unofficial arch linux image (https://www.olimex.com/forum/index.php?topic=1856.0). The same. I tried cp, dd or Windows Disk Image Writer. The A20 does not show up in network, as I understand, this should be normal with the official image because ethernet is not enabled from boot. But with the arch image also no network. The network interface on the A20 is green and sometimes blinks yellow though. What else could I try?

Thanks for any help

Daniel

[Lurch]

I think the eth0 interface is set up for dhcp - hopefully you have a working dhcp server.
The easiest thing is to connect a USB-3.3V-TTL converter onto UART0 on the A20 and use a terminal on your PC to watch the boot progress.  You generally see everything there. And you could edit files as root.
Mice and keyboards are generally v1.1 and may have trouble without a USB hub between them and the A20 USB port.
The converter is pretty much a must-have at this point.

[dave-at-axon]

I'd second the cable for debugging. It can really help to track down a lot of issues, even before the OS boots. In your case, with no display showing up, the serial output would show you whats happening. You only need 1 cable for all your boards

Can you try creating an Android SD just to test it with? With my A20 running Android and connected to HDMI and LCD, the HDMI does not show anything until the main Android screen appears.

[dannym]

daniel_:

I had the same problem. For me it was because it tried to use HDMI audio and my monitor hated that (got stuck, too).

If it's that, fix that by (putting Debian SD into another computer where you can see and...):

mount /dev/mmcblk0p1 /mnt/tmp

cd /mnt/tmp
cp uEnv.txt uEnv.txt.backup # one should already be there
echo "extraargs=disp.screen0_output_type=3 disp.screen0_output_mode=EDID:1920x1080p60 hdmi.audio=EDID:0" > uEnv.txt

umount /mnt/tmp

The important part for me was

hdmi.audio=EDID:0

without it I get nothing on the monitor at all and monitor gets stuck.

With it it works without problems.

Try it.

If it still doesn't work:

In order to enable ethernet, the insane (but working) way:

Boot from the SD without having any display (with connected USB keyboard).
Wait about 30 seconds.
Press Ctrl-Alt-F1. Release again.
Type
  root

Press Enter.
Type the password (I think it's olimex), press Enter.

Then type
  ifconfig eth0 192.168.2.5 netmask 255.255.255.0 up

Press Enter. At that moment the device should show up in the network. Try
  ping 192.168.2.5
from somewhere else.

If that doesn't work:

In order to enable ethernet, the correct way:

mount /dev/mmcblkp2 /mnt/tmp
cd /mnt/tmp/etc/network

cat << EOF >interfaces
# interfaces(5) file used by ifup and ifdown
auto lo
iface lo inet loopback
allow-hotplug eth0

auto eth0
iface eth0 inet static
        address 192.168.2.5
        netmask 255.255.255.0
EOF

chroot /mnt/tmp update-rc.d networking enable

Otherwise, there's an onboard LED which you can use in order to find out whether it booted fine.

For that, put in /mnt/tmp/etc/rc.local (before the exit 0):

echo 47 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio47_ph2/direction
for i in 1 2 3 4 5 6 7 8 9 10
do
  echo 1 > /sys/class/gpio/gpio47_ph2/value
  sleep 1
  echo 0 > /sys/class/gpio/gpio47_ph2/value
  sleep 2
done

Or something. After booting, the green LED between the barrel power connector and the headphone connector should slowly blink ten times.

(don't forget to do umount /mnt/tmp after everything - SD cards hate not being umounted)