Testing QinHeng Electronics HL-340 USB-Serial adapter

kernel-modulesserial portusb

I have Kubuntu 14.10 development workstation and recently I have bought a QinHeng Electronics HL-340 USB-Serial adapter. HL-340 is USB<---->Serial adapter and it is recognised by my kernel:

user@comp001:~$ lsusb
    Bus 007 Device 010: ID 1a86:7523 QinHeng Electronics HL-340 USB-Serial adapter
[..]

I am trying to initiate communication via this adapter with Raspberry Pi B+ board, but I am constantly failing.

Whatever text I send to the Raspberry Pi B+ via minicom, the traffic on the line is dead, I've checked with scope. I've double checked the Raspberry Pi B+ setup, the wirings (triple checked with multimeter), the scope wirings and the serial communication is dead. The port on Raspberry Pi B+ is working, because I've hooked up scope on transmit pin of serial port (on Raspberry Pi B+ side) and if I send text from Raspberry Pi B+ (via minicom under ssh tunnel), I get activity on the scope.

I cannot get data from PC via USB serial dongle. How do I test if the dongle works?

Best Answer

Is the adapter loading the right kernel module? I've heard that your device may be CH341 compatible:

sudo modprobe ch341

Related Solutions

How to send data from serial port over wifi

Use Ncat (http://nmap.org/ncat/). It is multiplatform, and it comes installed by default in many GNU/Linux distributions.

On your PC, listen with Ncat ( here we are using port 55555, but you can use any port):

nc -l 55555

On your CuBox, connect to the listener:

nc <Your PC's IP> 55555

Then if you type something in your CuBox, it will be sent to your PC (type something and press enter to see how it works).

With bash, you could easily redirect your serial data received in the CuBox through the USB to nc. Example (using screen for reading serial data from the terminal):

screen /dev/ttyUSB0 | nc 192.168.1.20 55555

Notice you should change your tty device and substitute 192.168.1.20 with your PC's IP.

Linux – PL2303/PL2303X USB-Serial driver

(Edit: updated based on @dirkt's comment. thank you)

I found an old manual for the device which explained "commonly communication cables use only 3 pins (RXD, TXD, and GND). This device has a hardware reset pin that is controlled by DTR signal from host."

I confirmed DTR = 1 by running sudo statserial /dev/ttyUSB0:


    Device: /dev/ttyUSB0
    
    Signal  Pin  Pin  Direction  Status  Full
    Name    (25) (9)  (computer)         Name
    -----   ---  ---  ---------  ------  -----
    FG       1    -      -           -   Frame Ground
    TxD      2    3      out         -   Transmit Data
    RxD      3    2      in          -   Receive  Data
    RTS      4    7      out         1   Request To Send
    CTS      5    8      in          0   Clear To Send
    DSR      6    6      in          0   Data Set Ready
    GND      7    5      -           -   Signal Ground
    DCD      8    1      in          0   Data Carrier Detect
    DTR     20    4      out         1   Data Terminal Ready
    RI      22    9      in          0   Ring Indicator

I then modified my C code to set DTR = 0 by adding the following:

#include <sys/ioctl.h>
...
// then on connect, added the following:
int DTR_flag = TIOCM_DTR;   // modem constant for DTR pin.
ioctl(fd, TIOCMBIC, &DTR_flag);   // sets DTR = 0

[Thank you @dirkt for your help, and everyone for viewing.]

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