[SOLVED] Device ttySAC0 is missing

[PTeck]

Hi all,

I'm working with an Odroid XU4, Ubuntu version 20.04.4 LTS, kernel version 5.4.167+. I want to use the expansion connector CON10 on the Odroid to operate an atmega board. I use avrdude to access the port and flash the atmega. The problem is that avrdude can't access the device port /dev/ttySAC0.

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avrdude: ser_open(): can't open device "/dev/ttySAC0": No such file or directory

When I look in /dev/ device ttySAC0 is not listed. I've check dmesg and it seems that the device does not get loaded.

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odroid@odroid:~/Documents$ dmesg | grep tty
[    0.000000] Kernel command line: console=tty1 console=ttySAC2,115200n8 root=UUID=e139ce78-9841-40fe-8823-96a304a09859 rootwait ro fsck.repair=yes net.ifnames=0  HPD=true vout=hdmi usbhid.quirks=0x0eef:0x0005:0x0004 smsc95xx.macaddr=00:1e:06:61:7a:39 false s5p_mfc.mem=16M
[    0.002950] printk: console [tty1] enabled
[    1.379323] 12c20000.serial: ttySAC2 at MMIO 0x12c20000 (irq = 62, base_baud = 0) is a S3C6400/10
[    2.293216] printk: console [ttySAC2] enabled
[    7.685854] systemd[1]: Created slice system-serial\x2dgetty.slice.

The strange thing is, that I have a another Odroid with a different eMMC with the same Ubuntu/Kernel version that works perfectly (/dev/ttySAC0 is available). I can't find the differences between the two.

Does anyone have any idea what the problem could be and what else I can look for?

[mctom]

Hi,

Check what's in /media/boot/config.ini. Somewhere near the end uart0 overlay should be mentioned.

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mctom@odroid0:~$ tail -n20 /media/boot/config.ini
; 933 / 825 / 728 / 633
ddr_freq=825


; Device Tree Overlay
overlay_resize=16384
overlay_profile=
overlays="spi0 i2c0 i2c1 uart0"

[overlay_custom]
overlays="i2c0 i2c1"

[overlay_hktft32]
overlays="hktft32 ads7846"

[overlay_hktft35]
overlays="hktft35 sx865x-i2c1"

[overlay_hktft_cs_ogst]
overlays="hktft-cs-ogst"

If it's not there, add uart0 to overlays list and reboot.

For the record...

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mctom@odroid0:~$ dmesg | grep tty
[    0.000000] Kernel command line: console=tty1 console=ttySAC2,115200n8 root=UUID=e139ce78-9841-40fe-8823-96a304a09859 rootwait ro fsck.repair=yes net.ifnames=0  HPD=true vout=hdmi usbhid.quirks=0x0eef:0x0005:0x0004 smsc95xx.macaddr=00:1e:06:61:7a:39 false s5p_mfc.mem=16M
[    0.002956] printk: console [tty1] enabled
[    1.314423] 12c00000.serial: ttySAC0 at MMIO 0x12c00000 (irq = 62, base_baud = 0) is a S3C6400/10
[    1.314855] 12c20000.serial: ttySAC2 at MMIO 0x12c20000 (irq = 63, base_baud = 0) is a S3C6400/10
[    2.254659] printk: console [ttySAC2] enabled
[   10.669299] systemd[1]: Created slice system-serial\x2dgetty.slice.

[mctom]

I also hope you are aware Odroid XU4 GPIO pins operate at 1.8V logic levels and you used a proper level shifter.
Otherwise your UART port may be simply damaged. :/

[PTeck]

Hey thanks for the quick reply!

Yes I'm using a level shifter. In fact I tested the same Odroid with another eMMC that works. So the hardware is fine.

My /media/boot/config.ini looks exactly the same as yours.

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odroid@odroid:~$ tail -n20 /media/boot/config.ini
; Sets the LPDDR3 memory frequency (MHz)
; 933 / 825 / 728 / 633
ddr_freq=825
; Device Tree Overlay
overlay_resize=16384
overlay_profile=
overlays="spi0 i2c0 i2c1 uart0"
[overlay_custom]
overlays="i2c0 i2c1"
[overlay_hktft32]
overlays="hktft32 ads7846"
[overlay_hktft35]
overlays="hktft35 sx865x-i2c1"
[overlay_hktft_cs_ogst]
overlays="hktft-cs-ogst"

I have several eMMCs that I have flashed all the same way and on a small percentage the device is unavailable. Does it make a difference if I put an eMMC in an Odroid for the first time and then use the same eMMC for another Odroid? So is there a difference between the initial boot process and the subsequent boot processes?

[mctom]

The first boot process is different, for example it expands the partition to take the whole space available on the medium, among other things, I imagine.

I'm out of ideas what is wrong in your case, but you may have just found an interesting bug indeed.

I'm sure someone smarter than me will help you out shortly.

[PTeck]

One of your eMMC modules seems to have a very old uboot in the hidden boot partition.
Here is a promising solution.
viewtopic.php?p=336661#p336661

[PTeck]

How did I not find this forum post?! I guess my google skills need to improve more. . Thank you very much for the answer, it fixed my problem!