This is an example of how to use the Panasonic thermal Printer EPT-1014LW2
offered by Allectronics.Com as catalog number PRNT-4.
If you'd like to be on the email list for any updates done to the site drop me a line at nvjames@aol.com.
The high current drivers TC427 are available from Digikey as is the TTL to RS232 converter, the MAX232.
At the moment the code is still in an experimental phase. The code is not commented (a heinous crime to
all programmers) and some parts are not even used. The code is set up to look for a starting character on
power up (at 1200 baud). If it is a '*' then the code enters a debug mode and it is assumed that the hardware
is attached to some form of terminal emulator (such as Hyperlink). A list of options are then displayed that
allow the user to experiment with various parameters in real time.
If a character other than the '*' is received on power up then the hardware assumes that it is in standard
printer mode. Characters are received via interrupt and put into a ring buffer. The code then examines the
pointers to the buffer, if a character is available it is then printer. Because of laziness on my part there is
no RS232 handshaking and if a lot of characters are thrown at the printer at one time the buffer might
become saturated and characters missed. This is one reason I operate the device at the relatively slow
baud rate of 1200 bps. Obviously a few extra tweaks to the code and the hardware could give a control
signal if that is what is required.
On the subject of the printer itself, I have found that just about the only relevant information has been the
pin out of the ribbon cable. Through trial and error I have worked out how to step the head motor and
the amount of time to spend exercising each phase. The same holds true for the heating element time. The
figures I have come up with (to get a readable image) bear no relationship to the spec. sheet. The trouble
with this last item is that the age of the thermal heads might be degraded by overheating.
One worry that I have with the hardware is that the motor is generating back emf when the motion is stopped.
I'm not to sure how the high current drivers will stand up to this, but everything seems OK at the moment.
Any comments would be welcome (blocking diodes ?).