Description:
The USB-341 “ReversePipe”™
Protocol Converter converts the output of a standard USB keyboard
to serial ASCII RS-232 format, effectively making it an ASCII keyboard. The USB-341 USB keyboard to serial ASCII Converter is powered from a 5V DC wall mount power supply which is
purchased separately. We recommend the VIP-211, for 100 - 240 V AC 47-63 Hz input, however, you may provide your own supply
(see specifications below).
Code Conversion for the VIP-345
The standard ASCII
code set is very common in RS-232 applications, but the standard
PC keyboard does not generate ASCII codes, but its own set of
scan codes. If ASCII codes are desired from a PC keyboard, translation
to ASCII is necessary.
The ASCII codes generated for USB keyboard keys are shown in the "PC Key Code to ASCII Translation"
Table. To use the table, find the
key in the table, then read the code in hex from the column/row
digits. The most significant hex digit is in the top row, the least significant is in the left column. For example, the @ sign will produce hex 40. Codes beyond
the standard ASCII table have been added to support keys found
on the PC keyboard, but not in the ASCII character set. For instance,
hex codes A0 to AB will be generated for the twelve function
keys, F1 to F12.
The ASCII code is generated when a keyboard key is pressed. No code is generated when a key is released. The Alt and Control keys, both left and right, are an exception, as shown in the Table above. Separate codes are generated when one of these key is pressed, and when it is released. If the Shift key is held down, upper case ASCII characters, or characters, such as the @ sign, will be generated.
The DB-9 connector on the
USB-341 transmits data on Pin 3, and Pin 5 is ground.
The USB-341 uses the following RS-232 format: 1 start bit, 1
stop bit, 8 data bits, and no parity.
In addition to the default baud rate of 9,600 baud, 4,800 baud and 19,200 baud are available.
|