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calculator printer hacking

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niele84

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hello, i have in mind to hack a calculator printer to use the small printer inside for my project.
i bought a small canon tp 7 for my porpuose.
But i have some question,how can i understand or sniffer communication between the processor and the printer embedded?
Thanks
 
Hi,


If i understand your question right, you want to use a calculator printer for your own purposes with your own circuit.

In that case, it is usually easier to interface to the keyboard itself if you can tolerate some slower communications.
That way you would be using the entire calculator rather than just the printer itself.
I wouldnt doubt it that they used a chip to drive the printer that also scans the keyboard anyway.
 
hello,thanks for your reply.
I cannot use the keyboard to print,cause i would print some symbol and not number.
I thought that is some eeprom where the chacarcter are stored and if so i can reprogram this to print my own symbol.
But if not so, how can i sniffer the communication between the cpu and the printer mechanism to know how interface my own circuits?
 
You need to discover exactly how it's driven, and duplicate that - a cheap calculator could use any kind of system. I presume you do know that you can buy printer mechanisms complete with datasheets and simple connections?.
 
It's going to be a simple impact dot matrix printer. Probably not that many pins and one or two stepper motors to drive the paper and the left and right motion. You send short impulses to the pins and they pop out stricking the ribbon and hitting the paper transferring the ink while the stepper is driven along the paper and then fed after each line. You can determine what voltages/currents the pins need for operation using an o'scope. The real hard part is simply finding all the pinouts and getting the printer module out of the calculator intact, and that might not be too difficult. Small line printers like that tend to come as discrete modules.
 
hello,thanks for your reply.
I cannot use the keyboard to print,cause i would print some symbol and not number.
I thought that is some eeprom where the chacarcter are stored and if so i can reprogram this to print my own symbol.
But if not so, how can i sniffer the communication between the cpu and the printer mechanism to know how interface my own circuits?


Hi again,


At the very least you probably would need some sort of logic analyzer, or perhaps a dual trace scope
and look at all the pins and see what signals are being generated for certain characters. Once you look
at several characters you could probably deduce what you have to do to get a certain character to
print out. You certainly have your work cut out for you though for sure.
Maybe Nigel can post some links to some printer mechanisms that you could look at and that would be
so much easier to work with.
 
really i didn't know that.
are they cheap like this printer?
I were looking for this mechanism in the whole net,but nothing found.
Could you help me?
I need a dot printer matrix with at least 9 dots.The printing speed does not import so much to me.
Thanks a lot for your help and your speed.
Thanks also to the forum,that is one of the best i ever tryed.
 
Good price on that printer Harvey, but it's a thermal printer not a dot matrix, not sure if this matters, but you're going to be stuck with whatever charactor set is built into it, unless you want to modify it, for the price though it looks like a really good deal. The site Nigel posted looks good but I'd be a little wary, there are no prices listed and the only naked dot matrix line printers I've ever seen are in the digikey catalog and they're 150+ dollars each.
 
Good price on that printer Harvey, but it's a thermal printer not a dot matrix, not sure if this matters, but you're going to be stuck with whatever charactor set is built into it, unless you want to modify it, for the price though it looks like a really good deal. The site Nigel posted looks good but I'd be a little wary, there are no prices listed and the only naked dot matrix line printers I've ever seen are in the digikey catalog and they're 150+ dollars each.

Think thermals are still dot-matrix. The ones with ribbons, are impact dot-matrix. Anyway, saw those for a while on that surplus site, and thought about it a few times. Seem like it could be useful, since it's wired for serial, and will also receive IrDa, should be microcontroller friendly. Wouldn't know about custom characters though, probably, but least it gives a model number to look up, and see what can be done with it. Small, light, low power, and cheap. Not too sure what The OP is planning to do, but didn't sound like he was looking to sink a lot of money into this.
 
The way thermals work though if it's driven properly it has far superior resolution, several times that of an impact dot matrix, and because there's no physical impact required the repeatability and resolution are better, but you do need special paper.
 
Hi,


Not sure if anyone here remembers the TI58 calculator, that you could by a dot matrix printer for.
Well, i had the calculator and the printer and yes it was a thermal printer and the paper for it was
a little on the expensive side. Fairly nice printing though.
That was way back in the 1980's.
 
I want to explore both of this printer features.
so i need to buy those two type.
the thermal dot matrix printer can be found everywhere on internet,but the impact type not.
why the impact dot-matrix printer are so hard to find?

And there is some article somewhere in internet that explain how control such device?

Thanks a lot for everyone that had reply thi post. i'm understanding more in one day asking to you that in months finding info in internet.
 
Over the long term a well made thermal printer will outlast a well made impact printer by an order of magnitude. Considering that the resolution and repeatability of a thermal is that much higher as well and economy of scale has somewhat dealt with the cost of the paper, as almost all receipt printers you'll find are all thermal now, it's nearly as cheap as ticker tape paper, and never requires ink cartridges.

If you're interested in thermal printers snatch up one of those units that Harvey link, I find it hard to believe you could find a better deal anywhere else. Impact printers are still used because they can print on multi-part paper, however due to the speed with which modern thermals can print being more than twice as fast it's not such a penalty.

One VERY important thing to note is thermal paper does no age well. It tends to yellow, and is totally unsuitble for high heat or direct exposure to sunlight or even mild chemicals as some chemicals will cause the paper to go completely black or even erase. Sometimes ink on paper is the better choice, even with all the downsides.
 
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