1、 The 485 communication level voltage of the printer is 3.3V, so the connected voltage should not exceed the power supply voltage of the 485 chip inside the printer to meet the electrical conditions (the normal voltage range for stable communication is between 2.5-3.3V).

2、 If it is connected to a 3.3V RS485 communication interface, it can be directly connected to the interface. If it is connected to an RS485 communication interface larger than 3.3V, it is generally not recommended to communicate directly. It is necessary to add a resistor between the A and B lines of RS485 and adjust the communication voltage appropriately (currently, a 20K resistor can be used to reduce the 4.75V level voltage to 3.25V, and there is still a 3.05V level voltage after connecting the printer, which is within the normal communication voltage range). The specific communication should be able to communicate normally. When the communication line is relatively long, a resistor can be directly used.

III The communication level voltage of RS485 is ordinary communication and is not easily damaged compared to RS232.

The above are temporary adjustment methods for using 485 communication interface under different conditions;

If it is determined that the communication distance is short, but the 485 communication level voltage at the control end is determined to be greater than 3.3 ≤ 5V, we can add a 20K SMT resistor to the reserved position on the printer's circuit board to solve this problem.

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