ur question need more elaboration now ur thermal printer works on serial or parallel communiction
if parallel here r some basic rules
• Pin 1 carries the strobe signal. It maintains a level of between 2.8 and 5 volts, but drops below 0.5 volts whenever the computer sends a byte of data. This drop in voltage tells the printer that data is being sent.
• Pins 2 through 9 are used to carry data. To indicate that a bit has a value of 1, a charge of 5 volts is sent through the correct pin. No charge on a pin indicates a value of 0. This is a simple but highly effective way to transmit digital information over an analog cable in real-time.
• Pin 10 sends the acknowledge signal from the printer to the computer. Like Pin 1, it maintains a charge and drops the voltage below 0.5 volts to let the computer know that the data was received.
• If the printer is busy, it will charge Pin 11. Then, it will drop the voltage below 0.5 volts to let the computer know it is ready to receive more data.
• The printer lets the computer know if it is out of paper by sending a charge on Pin 12.
• As long as the computer is receiving a charge on Pin 13, it knows that the device is online.
• The computer sends an auto feed signal to the printer through Pin 14 using a 5-volt charge.
• If the printer has any problems, it drops the voltage to less than 0.5 volts on Pin 15 to let the computer know that there is an error.
• Whenever a new print job is ready, the computer drops the charge on Pin 16 to initialize the printer.
• Pin 17 is used by the computer to remotely take the printer offline. This is accomplished by sending a charge to the printer and maintaining it as long as you want the printer offline.
• Pins 18-25 are grounds and are used as a reference signal for the low (below 0.5 volts) charge
for more information consult the data sheet of your thermal printer
---------- Post added at 12:46 ---------- Previous post was at 12:44 ----------
1. Write the byte to the Data Port .
2. Check to see is the printer is busy. If the printer is busy, it will not accept any data, thus any data which is written will be lost.
3. Take the Strobe low. This tells the printer that there is the correct data on the data lines.
4. Put the strobe high again after waiting for specified delay(should be in mili second) than put the strobe low.