Amstrad NC100 printer question

[agardiner]

Hi,

I recently purchased an Amstrad NC100 which I am enjoying playing with. I have a question regarding printers if anyone can help. I know it supports dot matrix printers and some canon inkjet, but ideally I would like to connect it up to an old thermal receipt printer (with parallel interface). I don't yet own such a printer which would appear to cost around £40 on ebay.

This would allow simple printing of basic listings etc. Does anyone know if such a printer would work?

Thanks,

Adrian.

[julie_m]

The Amstrad NC100 has both RS232 serial and Centronics parallel interfaces, and can drive a printer attached to either.

If your receipt printer has a standard Centronics interface, the NC100 should certainly be able to print text to it. Special effects e.g. bold, underlining and graphics will depend on whether it emulates an Epson, IBM or HP LaserJet well enough.

[ortek_service]

Phil, Chris and I have recently bought some thermal 'till' roll printers, that apparently Adafruit sold for around £40, but were around a quarter of that on Aliexpress.

But these had (TTL-level optional) 'RS232' Asynchronous Serial interfaces, rather than Centronics interfaces, which the modern ones don't have AFAIK.
So if the ones for sale really are much older ones, then if you can find what make / model these are, then can probably find some more info on the 'net somewhere as to exactly what interfaces they have.

But in theory the NC100 should work with either of these, But there may be some issues when trying to print listings as to whether the printers add a line-feed on carriage return - Old dot-matrix printers used to have a DIP-switch to select this / choose between Epson or IBM compatible control codes modes.

Phil had written routines for the SC/MP to print basic listings from NIBL on the SC/MP processor, specifically for these modern ones. So we didn't have that issue with these.
And it may be possible to do something similar on the NC100.
- There may also be issues with line-wrapping, as these printers will be rather-less than 80columns wide. So not sure how they handle line-wrapping / whether this is automatic.

[agardiner]

Thanks both. Any idea if the V-Tech VT-25 thermal printer might work? I cannot find out much about it other than it was intended for various v-tech toys, but from the manual of one such 'pre-computer', the following suggests it might be standard parallel.... see attachment.

[agardiner]

Took a punt and bought the V-Tech printer. Will report back here for anyone who is interested on how I get on once it arrives!

[agardiner]

Quick update for anyone following this thread. The V-Tech printer arrived but did not work at all. It seems that despite have a fairly standard parallel interface, (V-Tech toys would happily drive standard printers) the printer has no way of being put 'on-line' and thus the Amstrad doesn't recognise that a printer is attached. I imagine that the V-Tech printer uses a couple of pins on its connector to sense that it is connected to an actual V-Tech product.

[ortek_service]

Sorry to hear it didn't work with your Amstrad NC100

I did find this thread from last year, where I presume someone got it working with an Atari? computer:
https://forums.atariage.com/topic/368266-poor-printing-quality-on-vtech-vt-25-thermal-printer/

I'm not sure what the NC100 parallel port interface is like and whether (although it isn't a PC, being Z80 based - More like a 'Sinclair' Z88?) it is similar to a PC that doesn't quite have a full Centronics interface - as only has 25pins rather than 36pins.
So maybe some extra ones are required on pins >25 on the 25way D (= pins 14-18, 31-36 ? on the Centronics connector)

https://www.blackbox.nl/en-nl/page/29813/Resources/Technical...cs-connectors/pinning-centronics-36

There are 4 'Undefined' signals on this connector, so you could maybe check if these are connected to anything inside the printer.
Does the V-Tech printer actually use a full 36way connector / cable to the V-Tech 'Toys' ?

Pin13 of the Centronics Interface is 'Select', and should be connected on a standard PC Interface (to Pin13 of the 25way D?)
So may be worth ensuring this is going high.

Also, it might be worth trying a standard PC parallel interface / a USB to parallel converter, in case the NC100 isn't quite 'PC standard'.

[agardiner]

Interesting, thank you. The printer has an integrated cable with a standard D plug on the end. I will pull it apart and have a look at some of the connections you mention.

From its own test print, the quality is shocking which appears to be a common issue with these, so not going to waste too much time!

[ortek_service]

Is that a 25way D Plug?

I hadn't realised it had a built-in 'Test' mode (that was common on larger Epson etc. dot-matrix printers). So it may be the case that all they did on that atariage forum was use the test-mode - The print quality was rather bad, so it was quite-difficult to read what it had actually printed!

I presume you may have also tried some more-recent paper to that what it came with?

When I recently tried one of those more-modern 'till-receipt' serial-interface printers, I did at first have problems with print-quality and had tried swapping paper etc with someone else's.
But I discovered shortening the power cable seemed to resolve it - I already was using a higher input voltage than its min. with PSU's current limit at max 4A.
But it seems there are very-high surges, as it prints, that maybe the PSU regulation wasn't responding quick-enough to, and maybe really needed some bulk capacitance near to the printer to help deliver the high peak currents when the print-head is heating the 'dots' on the paper.
- Unusually on these more-modern ones, the head doesn't actually move and just consists of a line of 'dot' drives the whole-width of the paper. So appears to print the whole of each line oi dots in parallel, which no-doubt result in very-high peak currents.
.

[agardiner]

So on this one, a) it is battery operated from 4 C cells, so no power cable issues and I used fresh batteries. The head on this printer does move; I suspect this is actually a poor design choice and the primary cause of rubbish print quality. I tried fresh paper. And yes, it is a 25 pin D plug.

Overall this printer was sold as a toy to connect to V-Tech's line of child 'first' computers, so it was probably never up to much, a bit like V-Tech's rubbish camera. However, if the quality is a bad as it seems now, then it I would imagine there were a lot of very disappointed kids back in the day!

[ortek_service]

I presume this wouldn't be too-happy with NiMH cells, as might only get 4.8V from these, which may be a bit too low for a 5V supply. Although even with 6V from Alkalines that could be a bit marginal as 1.1V/cell is normally the end-point for these and they will rather dip a bit under-load compared to NiMH cells (just not as bad as Zinc Carbon ones)
And they didn't give you an external DC supply input (I remember my first Brother HR5 (portable A4) Thermal printer ran off D cells, but also had a DC power-input for an (optional, relatively-expensive) 6V 1A? mains-PSU. So I used to run it off my home-built variable bench PSU)


I think back then, the technology was limited to moving the head and they hadn't developed (not at low-cost, anyway) a fixed whole-width head / driver circuitry that could do all the dots in a line in parallel.

I assume the 25way 'D plug (not really an official Centronics-standard connector, but then the Beeb just a 26way header and most computers didn't have the full 36-way Centronics connector) on this is wired to be compatible with the IBM Parallel port?
(Maybe it / whatever the NC100 uses isn't, and that is the trouble?)

If you get a DMM on diode-test, with positive to the shield / a ground pin, you can probably see which pins have any internal connection / direct-connection to ground. Which should allow you to see which pins are actively used for signals / maybe a +5V supply pin.

[TonyDuell]

Originally Posted by ortek_service

I think back then, the technology was limited to moving the head and they hadn't developed (not at low-cost, anyway) a fixed whole-width head / driver circuitry that could do all the dots in a line in parallel.

Hewlett-Packard had full-width non-moving thermal printheads in the HP9810 and HP9820 desktop calculators in 1972. OK, they were only 20 characters/line or so. The HP9866 printer (about the same time) did a full 80 character line but the non-moving head was built from 4 modules. The printer in the HP9845, etc, had a full-width non-moving thermal printhead, late 1970s or so.

But those are not 'low cost'

Originally Posted by ortek_service

I assume the 25way 'D plug (not really an official Centronics-standard connector, but then the Beeb just a 26way header and most computers didn't have the full 36-way Centronics connector) on this is wired to be compatible with the IBM Parallel port?
(Maybe it / whatever the NC100 uses isn't, and that is the trouble?)

How many wires come out of the printer end of the cable to its PCBs? Any helpful markings on the PCBs? Are there enough for a parallel interface (7 or 8 data lines, strobe, busy, ground)?

[ortek_service]

Well may be not too surprising that HP did full-width heads rather earlier - but they were never exactly at 'toy' prices!

I was thinking by doing diode-junction/continuity checks, that would be a quick way of identifying which pins were being used.
It seems there is very-little info in the printers online, but it did state they had a parallel / Centronics interface in one place at least (Rather than using serial on a standard 25 'D' for that)
However, if the OP is happy to open-up the printer and take some photos / do some wire-tracing, then that could be very useful.
- I assume there is a cable coming out of the PCB, rather than them using a PCB-mount 25w 'D' connector, which would then involve some tracing of tracks to RevEng this part.

[ortek_service]

Originally Posted by ortek_service

Sorry to hear it didn't work with your Amstrad NC100

>>
>>
I'm not sure what the NC100 parallel port interface is like and whether (although it isn't a PC, being Z80 based - More like a 'Sinclair' Z88?) it is similar to a PC that doesn't quite have a full Centronics interface - as only has 25pins rather than 36pins.
So maybe some extra ones are required on pins >25 on the 25way D (= pins 14-18, 31-36 ? on the Centronics connector)
>>
>>
Pin13 of the Centronics Interface is 'Select', and should be connected on a standard PC Interface (to Pin13 of the 25way D?)
So may be worth ensuring this is going high.

Also, it might be worth trying a standard PC parallel interface / a USB to parallel converter, in case the NC100 isn't quite 'PC standard'.

Well I did try and find a pinout for the NC100's Parallel-port, but can't seem to find this (never mind a schematic) - Not even in the Advanced User Guide 3rd party book: https://archive.org/details/amstrad-notepad-advanced-user-guide

Although, I did find a block diagram that shows it just has STROBE and Busy, as well as ACK & D0..D7.
https://www.cpcwiki.eu/index.php/A_surgical_guide_to_the_Amstrad_NC
With insides-photos here: http://mycalcdb.free.fr/main.php?l=0&id=6391


So it seems this may lack all of the Centronics control signals, that a PC LPT port normally had:
https://www.lammertbies.nl/comm/cable/parallel
https://vallder.com/product/lpt-cable/

And could be worth trying it on a standard PC, if you have one that still has a Parallel port.
- As well as trying to work-out what signals the V-Tech printer actually uses.

I did see in an article about using the NC100 Parallel port (for I2C): https://www.ncus.org.uk/utils.htm that the end two pins 24 & 25 might be +ve (Supply, rather than ground?). Which could lead to problems if using a standard cable with all these grounded at the other end. But maybe this was an error?

[agardiner]

So it doesn't surprise me that the NC100 does not have all the control signals, as it was a fairly basic device.

Anyway, I have decided to return the printer rather than open it up, as for the price I paid it should at least print its test printout (which the seller claimed it did). I was never expecting miracles, but will look out for a much cheaper unit at some point to have further play around with.

[ortek_service]

I think most 8bit Computers like the Beeb and Amstrad CPC etc. only had the minimum signals on their Parallel-port: Just Datalines plus Strobe, Busy & not even Ack. With mainly only PC's having all the extras ones, that it would be surprising if the VTech VT-25 / their Precomputers used.

But unfortunately there's very-little info on these Vtech printers/computers online - I can't even find a copy of the VT-25 printer manual, although the Precomputer etc manuals are still lurking buried on their website: https://www.vtechkids.com/assets/data/products/%7BEFFDA597-D...7D/manuals/PreComputer_Prestige.pdf
https://www.vtechtoys.com/assets/data/products/%7BCE13FA1C-F...D/manuals/PreComputer_Unlimited.pdf

- with no links to these from their manuals search: https://www.vtech.co.uk/support/product_manuals

However, the manuals aren't too helpful as regards technical details, and no-one seems to have reversed-engineered these so far.

I see the VT-25's original box photos do show clear printing, but everyone else online seems to have bad printing from these!

So sorry to hear you too have been unsuccessful with getting acceptable quality from it.


It doesn't seem that thermal till-roll printers are now available with a Centronics interface, but many are still sold with a Serial Interface (and also USB) - Just have to chose the right model as some maybe USB-Only or TTL-level (which will also be the opposite polarity) only.
The both RS232 & TTL levels Async serial + USB one I got was from here:
https://www.aliexpress.com/item/1005005664126996.html?

- Although it has increased in price a bit to £20 from when I bought it for around £15? which was about the cheapest with both level / polarity serial options.
And there may now be cheaper ones, like: https://www.aliexpress.com/item/1005006018103210.html

[agardiner]

Thanks for your further post. I have found one or two old thermal printers on ebay with parallel ports, so they are around 2nd hand. I will keep my eyes open for one at a suitable price for a punt and have another go.

[ortek_service]

Although the Amstrad NC100 can also print to its RS232 Serial port.

So you can also use a serial-only printer (Less-common back then, with Parallel usually the default and Serial an option on many A4 etc. size paper dot-matrix & Thermal-transfer printers)
- either a vintage model, or a more-recent fixed (full paper-width) head type of (not special-HP) general-purpose printer.

[agardiner]

Regarding the serial port, I don't have another computer (at present) with a serial port and would like to try getting documents off the NC100.

I bought a USB serial cable, but could not get it to work; the PC just wouldn't talk to it. I am considering buying an RS232 logging device, which supposedly will record a text file of the data stream onto a flash drive. An interesting prospect. Any thoughts?

[julie_m]

If you are doing anything at all with RS232 serial connections, you absolutely need a device with back-to-back high-brightness LEDs with suitably large series resistors on the "TXD" and "RXD" lines.

On some devices, TXD is an output for the data it is transmitting; and on other devices, TXD is an input for the data being transmitted to it.