Dragonboard UART


#1

Hi all,

I’ve got my Dragonboard 410c all up and running – apart from serial access. I bought a TTL-232RG-VIP-WE adapter and have connected it according to a photo of a working setup that I was sent :slight_smile: but I get no output from the device at all. How can I figure out what the problem is?

Cheers,
mwh


#2

hi,

The VIP variant of the cable requires a reference input signal at 1.8V, since it can operate with signal from 1.8 to 5V, unlike TTL-232RG-VREG1V8-WE which doesn’t need the reference input signal.

Did you connect the red wire to 1.8V signal?


#3

Yes. I wish I’d found the recommendation for the TTL-232RG-VREG1V8-WE before buying the VIP one. I had a hard time getting the red cable into the connector, it seemed to have too much solder on it, so I guess it’s possible I broke the wire enough to not have a stable connection or something.


#4

this is what I use:

usb cable

some wires


#5

Hi,

I’m also having problem here. Linux is booting fine, usb network running fine too.

I’m trying like this:

  1. in a ssh session, put some testtraffic to serial port:

root@linaro-developer:~# while true; do echo alive | tee /dev/ttyMSM0; sleep 0.5; done

  1. in another session, watch linux idea about the serial port:

root@linaro-developer:~# watch cat /proc/tty/driver/msm_serial

0: uart:MSM mmio:0x078B0000 irq:135 tx:10154 rx:70 brk:70 RTS|CTS|DTR|DSR|CD
here I see that tx counter is counting up which is hopeful.

  1. using a scope probe, search on pinheader for output activity.

I’ve tried to “steal” 1.8V at pin 35 (should be there according to docs) so
that my ttl/rs232 could get correct Vio, but unfortunately there is no 1.8V there.
I’ve noted there is 1.8V on other pins but they have other functionality according
to docs (like uart1 and i2c0/1) so not sure I can steal from there… using a scope
to just be able to spot the correct output pin should still work though.
UART0_TxD should be at pin 5 according to docs, no output there, no output on any actually.

Anyone having success with uart?

Where is the promised schematics? :slight_smile:


#6

@saxofon: the serial console is on UART1, not UART0. also which USB/UART cable do you have?


#7

@ndec: thx for quick reply!

Oki, well don’t see any activity on UART1 either (using scope). Tried all pins on the J8 header.

I’m using a cp210x based usb/uart dongle (usb in one end, uart ttl in other). It is normally down
to 3.45Vio but it is possible to patch it downto 1.8V (which is why I need 1.8V from somewhere :wink: )


#8

update: booting target and i see now activity on uart1tx so now it is just to find out where I’m making some mistake… :slight_smile:
Thx for quick help.


#9

oki, up and running… turns out I can skip Vio completely (just cutting the normal path of Vio on the module
and not insert 1.8V at all) and then I get the bootlog:

Format: Log Type - Time(microsec) - Message - Optional Info
Log Type: B - Since Boot(Power On Reset), D - Delta, S - Statistic
S - QC_IMAGE_VERSION_STRING=BOOT.BF.3.0-00261
S - IMAGE_VARIANT_STRING=HAAAANAAA
S - OEM_IMAGE_VERSION_STRING=C-BPATTH
S - Boot Config, 0x000002e1
S - Core 0 Frequency, 0 MHz
B - 1544 - PBL, Start
B - 3489 - bootable_media_detect_entry, Start
B - 95659 - bootable_media_detect_success, Start
B - 95663 - elf_loader_entry, Start
B - 97234 - auth_hash_seg_entry, Start
B - 97446 - auth_hash_seg_exit, Start
B - 111897 - elf_segs_hash_verify_entry, Start
B - 171485 - PBL, End

Ubuntu 15.04 linaro-developer ttyMSM0

linaro-developer login: root (automatic login)

Last login: Mon Feb 16 20:55:09 UTC 2015 on ttyMSM0
root@linaro-developer:~# [ 69.200791] wcn36xx wcn36xx: Failed (-11) to read macaddress file wlan/macaddr0, using a random address instead

root@linaro-developer:~#
Ubuntu 15.04 linaro-developer ttyMSM0

linaro-developer login: root (automatic login)

Last login: Mon Feb 16 20:55:09 UTC 2015 on ttyMSM0
root@linaro-developer:~# [ 69.200791] wcn36xx wcn36xx: Failed (-11) to read macaddress file wlan/macaddr0, using a random address instead

root@linaro-developer:~# cat /proc/tty/driver/msm_serial
serinfo:1.0 driver revision:
0: uart:MSM mmio:0x078B0000 irq:135 tx:8754 rx:40 RTS|CTS|DTR|DSR|CD
root@linaro-developer:~#

Would be nice with a 1.8V though to have it more correct, do you know if there is some other good place to steal it from (as pin 35 isn’t alive)?
I image very little current draw,


#10

it should be on PIN35. I think i remember we discussed that internally. The specs requires the 1.8V to be there, for mezzanine boards, so we need to enable the regulator behind that pin. I will check again, and probably include that in the next release.

in the mean time, the following patch should enable the 1.8V signal on pin35:

--- a/arch/arm64/boot/dts/qcom/apq8016-sbc.dtsi
+++ b/arch/arm64/boot/dts/qcom/apq8016-sbc.dtsi
@@ -220,3 +220,9 @@
 		};
 	};
 };
+
+/* default regulators required for mezzanine boards */
+&pm8916_l15 {
+	regulator-always-on;
+};
+	

#11

Great support! I’ll use that patch in meantime.


#12

Do you know if this patch was ever merged in.
I need a 1.8V reference for level shifting and I’m also not seeing any voltage on pin 35.


#13

yes, it was (in our Linux releases, and also upstream in mainline kernel). Which release are you using?


#14

I just realized that this post is for the DragonBoard.
I’m using the Hikey960 and having a similar problem.
FWIW the 4.9 kernel.


#15

ah, i would recommend you open a discussion on the hikey forum then. you will get attention from the right people then.


#16

I think I found a relevant discussion for the Hikey960.
Linking here for future people landing here from Google.
Thanks for your time.