so i try some keyboard sample code
and i have alien message again from my serial monitor,
so i believe there is some problem between my mega 2560 and usb host shield
Based on this issue with the library you are using, and the picture of the scanner which appears to show CH340G usb chips, it seems it may not work:
However, you may be able to connect a serial port of your mega directly to the tx and rx outputs of the scanner usb micro socket marked uart . Tx —> Rx, Rx—> Tx, grounds connected together. That is, without the host shield. You may have to hack a usb cable and/or do some soldering.
Read the chosen Serial port at 9600 with an Arduino sketch.
Can you find an on-line schematic for that device ?
Instead of soldering, you may be able to remove the two jumpers on the scanner and connect a cable between the pin marked S-RX to the TX of one of your mega's serial ports and also the pin marked S-TX to the RX of the same mega serial port.
You need also a common ground connection between the mega and the scanner.
Write a sketch to read the chosen mega serial port and write the data read (at 9600baud) to the serial console.
Sometimes it is easier to buy a ready made solution if such a thing is available.
But you can also try what I suggested in post #13. That needs only 3 connections between the scanner and the mega. You’ll need to write a small program (5 or 6 lines of code) to read the scanner input and print it.
Without a schematic or better documentation, it is difficult to be sure about how to use the interfaces.