[Bug 213771] ch341 USB-Serial converter receives but does not send

bugzilla-daemon
2021-07-21T19:00:10Z

--- Comment #2 from Luzemario (luzemario@gmail.com) ---
Sorry. Description was copied from former bugtracker to make it self-conteined.
Iw was tested within Ubuntu and Alpine, with Linuz original kernel. Please
ignore Ubuntu-specific information.

*********

This device works flawlessly on Windows XP with native driver, both as a
physical machine or inside a VM. It appears on XP's device management as "USB
2.0" name.

On Ubuntu, Shorting pins 2 and 3 of DB9 connector does not give back characters
sent (no echo), nor typed strings are sent to other RS232 devices, despite of
communication settings. Characters from remote devices are correctly received.
Using a null modem cable to other RS232 terminal shows that the local terminal
receives, but does not transmit.

Its worth to mention: passing through the device to a guest virtual machine
(KVM) running Windows XP makes it work correctly with XP driver inside the
guest OS. Bringing back the device stops transmitting. Only receive works.

Tested with the version below:
NAME="Ubuntu"
VERSION="20.04.2 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.2 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal

Kernel:
Linux host 5.4.0-66-generic #74-Ubuntu SMP Wed Jan 27 22:54:38 UTC 2021 x86_64
x86_64 x86_64 GNU/Linux

Device ID:
ID 4348:5523 WinChipHead USB->RS 232 adapter with Prolifec PL 2303 chipset

Modinfo:
filename: /lib/modules/5.4.0-66-generic/kernel/drivers/usb/serial/ch341.ko
license: GPL v2
srcversion: 8F5F64E72BDA4E76E6F4F4D
alias: usb:v4348p5523d*dc*dsc*dp*ic*isc*ip*in*
alias: usb:v1A86p7523d*dc*dsc*dp*ic*isc*ip*in*
alias: usb:v1A86p7522d*dc*dsc*dp*ic*isc*ip*in*
alias: usb:v1A86p5523d*dc*dsc*dp*ic*isc*ip*in*
alias: usb:v1A86p5512d*dc*dsc*dp*ic*isc*ip*in*
depends: usbserial
retpoline: Y
intree: Y
name: ch341
vermagic: 5.4.0-66-generic SMP mod_unload
sig_id: PKCS#7
signer: Build time autogenerated kernel key
sig_key: 1E:07:0D:94:23:77:98:99:05:31:F3:76:E8:6B:76:12:7C:83:9E:05
sig_hashalgo: sha512
signature: 50:CE:79:92:87:EA:82:77:A9:25:A3:B7:F2:B3:ED:63:FE:85:EB:61:
7A:31:C5:9E:E5:78:E5:44:C6:FE:5D:74:4A:60:B6:0A:94:3F:C3:70:
0B:6D:27:A6:89:F7:D2:AC:8E:71:AC:0D:AF:5D:3A:19:07:18:F9:7C:
B8:3C:47:DF:18:4D:13:C9:F8:45:AC:81:19:B0:DE:57:16:1A:F5:C6:
AC:41:7E:E7:F2:6D:29:9C:14:A3:04:F8:9B:DF:8D:2E:9F:34:44:18:
A8:FF:C6:A4:AF:04:86:D5:6D:F2:4C:AD:D2:65:4C:63:0F:C1:82:E3:
28:20:F2:D4:80:86:1A:67:1D:A2:56:18:87:E2:AB:40:E6:6A:48:E5:
D7:D2:6F:6F:DB:05:20:B2:76:81:5C:0C:36:02:37:E9:A2:08:4E:53:
5E:9C:18:03:50:11:2D:E4:62:74:6E:CB:42:67:25:22:0C:F6:55:D8:
6F:E3:5A:15:AC:10:B7:F2:B7:C9:20:6C:19:ED:CC:7D:CC:CB:48:3B:
B0:5E:E3:ED:05:DF:DF:65:FF:19:AD:76:6E:40:D2:0B:F0:11:65:D5:
92:7D:C9:3A:32:BE:A8:13:CE:C1:DE:D9:73:0F:0A:0B:8A:08:55:2E:
41:9D:B9:9A:AD:EC:4C:7D:98:3A:52:38:DF:78:DE:33:F1:14:A2:1B:
AC:93:FD:30:76:A5:7C:AF:13:16:B8:5E:0B:73:A7:1F:20:E4:54:44:
07:A2:11:7F:D7:0E:B3:1C:A9:AA:73:76:0E:89:E0:D5:74:39:66:2F:
E8:14:93:EC:7A:B2:23:E0:CC:77:9F:CD:D9:99:CB:B0:14:21:1C:1F:
0C:E9:30:B8:C3:55:8F:49:FC:88:5D:EF:20:B9:0E:F2:88:28:5A:93:
08:4D:2B:76:64:85:D1:E0:1C:9C:4B:86:2C:DB:65:F6:D8:23:A0:8D:
1B:22:74:0C:B9:41:9E:57:5A:67:4C:CC:1F:E2:43:5F:C2:21:82:E6:
D4:C1:66:6F:30:54:27:2E:1D:22:8C:65:7F:93:C8:1D:C0:51:F0:7D:
7A:96:3A:3B:3D:C4:6E:69:DF:83:8A:85:0D:35:15:F9:5E:89:0F:D5:
9E:6F:A1:5F:39:CE:2A:88:57:97:DF:42:5C:70:12:4E:91:9E:1A:92:
49:99:C3:7B:38:12:B0:3A:D0:92:38:45:C7:74:3C:66:0F:A1:9C:C2:
9F:DC:A2:1B:DF:20:BB:F5:A5:F0:10:D6:6F:4F:C1:90:00:C3:F9:D8:
42:96:D2:28:FD:DE:21:33:6C:F4:7F:18:B2:ED:F9:A6:A4:4A:A5:4F:
26:7C:C0:F7:8B:A9:B3:2F:5A:5B:E2:B8

Demsg entries:
usb 4-3: new full-speed USB device number 6 using ohci-pci
usb 4-3: New USB device found, idVendor=4348, idProduct=5523, bcdDevice= 2.50
usb 4-3: New USB device strings: Mfr=0, Product=0, SerialNumber=0
ch341 4-3:1.0: ch341-uart converter detected
usb 4-3: ch341-uart converter now attached to ttyUSB0
---
ProblemType: Bug
ApportVersion: 2.20.11-0ubuntu27.16
Architecture: amd64
[...] # not relevant / stripped
DistroRelease: Ubuntu 20.04
InstallationDate: Installed on 2021-01-23 (50 days ago)
InstallationMedia: Kubuntu 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
MachineType: System manufacturer System Product Name
NonfreeKernelModules: nvidia_modeset nvidia
Package: linux (not installed)
ProcFB: 0 VESA VGA
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.4.0-66-generic
root=UUID=68929bb0-3af4-4634-8d5b-c2846910c077 ro locale=pt_BR quiet splash
vt.handoff=7
ProcVersionSignature: Ubuntu 5.4.0-66.74-generic 5.4.86
RelatedPackageVersions:
linux-restricted-modules-5.4.0-66-generic N/A
linux-backports-modules-5.4.0-66-generic N/A
linux-firmware 1.187.10
RfKill:

Tags: focal
Uname: Linux 5.4.0-66-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip libvirt lpadmin lxd plugdev sambashare sudo
_MarkForUpload: True
dmi.bios.date: 11/18/2016
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 0502
dmi.board.asset.tag: To Be Filled By O.E.M.
dmi.board.name: M5A78L-M PLUS/USB3
dmi.board.vendor: ASUSTeK Computer INC.
dmi.board.version: Rev X.0x
dmi.chassis.asset.tag: Asset-1234567890
dmi.chassis.type: 3
dmi.chassis.vendor: Chassis Manufacture
dmi.chassis.version: Chassis Version
dmi.modalias:
dmi:bvnAmericanMegatrendsInc.:bvr0502:bd11/18/2016:svnSystemmanufacturer:pnSystemProductName:pvrSystemVersion:rvnASUSTeKComputerINC.:rnM5A78L-MPLUS/USB3:rvrRevX.0x:cvnChassisManufacture:ct3:cvrChassisVersion:
dmi.product.family: To Be Filled By O.E.M.
dmi.product.name: System Product Name
dmi.product.sku: To Be Filled By O.E.M.
dmi.product.version: System Version
dmi.sys.vendor: System manufacturer