[Buildroot] [RPi 3B] ttyAMA0 serial port device doesn't exist on raspberry pi 3B
Oscar Gomez Fuente
oscargomezf at gmail.com
Tue Apr 19 11:23:31 UTC 2016
Hi everyone,
I'm using buildroot-2016.02 and I'm trying to make a rootfs for the
raspberry pi 3B. I've just used the raspberrypi2_defconfig. And everything
works fine except the serial port /dev/ttyAMA0.... I can see characters on
the serial port but they are garbage characters...
This is my config.txt, I'm using the bcm2710-rpi-3-b.dtb file:
-----
# Please note that this is only a sample, we recommend you to change it to
fit
# your needs.
# You should override this file using a post-build script.
# See http://buildroot.org/manual.html#rootfs-custom
# and http://elinux.org/RPiconfig for a description of config.txt syntax
kernel=zImage
# To use an external initramfs file
#initramfs rootfs.cpio.gz
# Disable overscan assuming the display supports displaying the full
resolution
# If the text shown on the screen disappears off the edge, comment this out
disable_overscan=1
# How much memory in MB to assign to the GPU on Pi models having
# 256, 512 or 1024 MB total memory
gpu_mem_256=100
gpu_mem_512=100
gpu_mem_1024=100
device_tree=bcm2710-rpi-3-b.dtb
dtparam=i2c_arm=on,i2c_arm_baudrate=200000
dtparam=spi=on
dtparam=watchdog=on
-----
And If I connect to my RPi3, I can see this with a dmesg:
...
[ 0.000000] CPU: ARMv7 Processor [410fd034] revision 4 (ARMv7),
cr=10c5383d
[ 0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing
instruction cache
[ 0.000000] Machine model: Raspberry Pi 3 Model B Rev 1.2
[ 0.000000] cma: Reserved 8 MiB at 0x38000000
...
So the .dtb file is loaded correctly.
And this is my cmdline.txt file:
------
console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 root=/dev/mmcblk0p2 rw
rootfstype=ext4 elevator=deadline rootwait ip=dhcp
-----
But if I list the devices on /dev, I can see these devices:
/dev/ttyAMA1 and /dev/ttyS0
With the same rootfs compiled, but using bcm2709-rpi-2-b.dtb instead of
bcm2710-rpi-3-b.dtb it works fine on my RPi 2B, and I can see:
/dev/ttyAMA0
It seems to be there is some problem with the bcm2710-rpi-3-b.dtb file. Any
suggestions?
Best regards.
Oscar Gomez Fuente
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