UART0 garbage characters

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Sebastián Sáez

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Jan 2, 2019, 4:37:35 PM1/2/19
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Hi everyone!

after install the last linux image in the emmc I can't use the UART0 anymore (screenshot attached )

All other function are working, I can do SSH using the softAP interface.

Any suggestions?
I already tried deleting uboot in emmc without lucky

This is my system:

debian@beaglebone:~$ sudo /opt/scripts/tools/version.sh
git:/opt/scripts/:[0ca42da8c7e3d81e9cbab71b1e2b0fad00bf79ca]
eeprom:[A335BNLTGW1ABBGW16063691]
model:[TI_AM335x_BeagleBone_Green_Wireless]
dogtag:[BeagleBoard.org Debian Image 2018-10-07]
bootloader:[eMMC-(default)]:[/dev/mmcblk1]:[U-Boot 2018.09-00002-g0b54a51eee]:[location: dd MBR]
kernel:[4.14.79-ti-r86]
nodejs:[v6.16.0]
uboot_overlay_options:[enable_uboot_overlays=1]
uboot_overlay_options:[uboot_overlay_pru=/lib/firmware/AM335X-PRU-RPROC-4-14-TI-00A0.dtbo]
uboot_overlay_options:[enable_uboot_cape_universal=1]
pkg check: to individually upgrade run: [sudo apt install --only-upgrade <pkg>]
pkg:[bb-cape-overlays]:[4.4.20190102.0-0rcnee0~stretch+20190102]
pkg:[bb-wl18xx-firmware]:[1.20180517-0rcnee0~stretch+20180517]
pkg:[kmod]:[23-2rcnee1~stretch+20171005]
pkg:[librobotcontrol]:[1.0.4-git20181227.0-0rcnee0~stretch+20181228]
pkg:[firmware-ti-connectivity]:[20180825+dfsg-1rcnee1~stretch+20181217]
groups:[debian : debian adm kmem dialout cdrom floppy audio dip video plugdev users systemd-journal i2c bluetooth netdev cloud9ide gpio pwm eqep admin spi tisdk weston-launch xenomai]
cmdline:[console=ttyO0,115200n8 bone_capemgr.uboot_capemgr_enabled=1 root=/dev/mmcblk1p1 ro rootfstype=ext4 rootwait coherent_pool=1M net.ifnames=0 quiet]
dmesg | grep pinctrl-single
[    1.063909] pinctrl-single 44e10800.pinmux: 142 pins at pa f9e10800 size 568
dmesg | grep gpio-of-helper
[    1.075590] gpio-of-helper ocp:cape-universal: ready
END


garbage characters

uart0.png


Yiling Cao

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Jan 3, 2019, 9:42:17 PM1/3/19
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correct UART rate and good ground connection?

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Sebastián Sáez

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Jan 8, 2019, 9:40:45 AM1/8/19
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Hey Yiling, thanks for the reply

After check the documantation and use the oscilloscope, with a friend we found that this issue is because I use in my custom cape a pull up resistor in pin P8-32 (button connected to this pin)

The pin P8-32 is LCD_DATA15 or SYSBOOT15 and the pull up to 3v3 set this pint to high. 
When you boot the bbone with the P8-32 not pressed, the processor set the cristal at 26MHz and the baud rate is 106500 not 115200
When you boot the bbone with the button in P8-32 pressed, crystal is set to 24MHz

The weird thing is that with Debian 8 I don't see this 

Here is the documentation

image.png



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