Only garbage characters; out of ideas

[jbrains]

Hi, folks.

I'm using a USB/Parallel port adapter to connect my Pop!_OS laptop to the RetroPrinter v4. After much trial and error, I have managed to send data to the RetroPrinter; however, the latter seems to make no sense of it. I have no idea what might be going wrong, so I don't know how to continue. I would be grateful for any suggestions.

I believe I have the defaults configured on the RetroPrinter, except for "output PDF", which I have turned off for the time being. Epson, 24-pin printer. I have configured an Epson generic 24-pin printer in CUPS on my laptop ("Epson 24-Pin Series" is the name of the printer driver). The resulting text file on the RetroPrinter is gibberish. I have tried printing with `cat file.txt | lp -P retro` with no luck so far.

What can I try?

Many thanks.

[RWAP]

The main reason for gibberish in the output is that the bit_depth setting needs to be set to 7 to work with your equipment. This defaults to 8 bits which is required for graphics printing mainly.

[jbrains]

Aha! That makes perfect sense. I will try that.

[jbrains]

The main reason for gibberish in the output is that the bit_depth setting needs to be set to 7 to work with your equipment. This defaults to 8 bits which is required for graphics printing mainly.

I tried 7 bits and the Epson generic 24-pin printer. Now I get text which is right-ish. The raw file has evidence of the correct forms of the words and many correct characters, but some obvious problems.

Code: Select all

H rt`rtdd vhth thd ddf`tlt hnrt`ll`thnn frnl thd RD b`rd th`t RV@P rdnt tr. Vhdn H bnntdd, thd ddvhbd v`r rttbj `t "`ttn,lnfhn". H h`d bnntdd hn thhr bnnfhftr`thnn:

, Dthdrndt b`bld
, HDLH b`bld
, TRB lntrd
, TRB jdxbn`rd

H rd`d thhr frnl <httpr:..vvv.rdtrnprhntdr,rtppnrt.bnl.vhdvtnphb.php>p<400"p400>

<blnbjptntd>

@ftdr `nx frdrh hnrt`ll nf thd rnftv`rd, thd RdtrnPrhntdr dndrn&t `ttn lnfhn. Vhth ` lnnhtnr pltffdd hn tn thd r`rp ph nn rt`rt tp, H h`vd tn v`ht fnr thd `ttnlnfhn hn tn f`hl ` fdv thldr, thdn @lt,F4 tn bld lhnd. Thdn fnllnvhnf ` fthdd nnlhnd, H fntnd th`t thhr prnbddtrd hdlpr tn rnlvd thd lnfhn hrrtd:

"

The string rendered as "@ftdr", for example, is the word "After" at the beginning of a sentence.

I'll continue to try various settings, but perhaps this outcome means a specific/known configuration I ought to try.

Thank you.

Epilogue: I have tried a few retro Epson printer drivers (LX-300+) with the same results. I have also tried the 9-pin printer driver and changing the Epson pins setting to 9 pins. No change. Maybe this consistency of outcome sheds light?

[RWAP]

The epson_pins setting only affects line spacing so that would not help.

That is a very odd issue - although I am guessing at what the actual original wording was....
For example, I think I can see "the RetroPrinter" but it is changed to "thd RdtrnPrhntdr"

in that case every 'e' character becomes 'd', every 'i' becomes 'h' and every 'o' becomes 'n'

It looks as though bit 0 is being ignored in each character which is odd.
That suggests it could be a broken pin on the GPIO connector of the Raspberry Pi or some oddity with the USB to parallel convertor.

It could potentially just be the handshaking signal - try changing:
/root/config/handshaking (try values between 0 and 4) - this affects the timing of the handshaking signal.

Rich

[jbrains]

Excellent! I hadn't noticed that pattern, so a single bit flipped might indeed fit.

I'm preparing to try with a PCIe Parallel port installed in a modernish PC. If this behaves differently, then I infer we'd suspect the USB/Parallel adapter. If it behaves the same, then do we suspect only the Raspberry Pi or possibly also the RetroPrinter itself?

Meantime, I'm installing Linux on this PC in order to try out the PCIe Parallel port.

Thank you.

[jbrains]

Aha! I have the same behavior (the off-by-one-character output) from a completely different PC sending data over a PCIe Parallel port and with a different Centronics cable.

What's in common are the Raspberry Pi and the Retro-Printer device.

Can you suggest how I could further isolate the problem, before I buy a new Raspberry Pi?

PS: I tried every setting for `/root/config/handshaking` and it seemed to have no effect.

Many thanks.

[RWAP]

Aha! I have the same behavior (the off-by-one-character output) from a completely different PC sending data over a PCIe Parallel port and with a different Centronics cable.

What's in common are the Raspberry Pi and the Retro-Printer device.

Can you suggest how I could further isolate the problem, before I buy a new Raspberry Pi?

PS: I tried every setting for `/root/config/handshaking` and it seemed to have no effect.

Many thanks.

Thanks for checking - it could be the alignment of the GPIO pins, but that is unlikely.

I have sent you a PM - as it is so difficult to get hold of Raspberry Pis at the moment, I will send a replacement Retro-Printer module

[PBarnertt]

I am having a similar issue. I can take the parallel printer cable and plug into the networked printer (which has a printer connection to) and print a perfect print job. However, I get gibberish as described when I attempt to print anything. So I have to assume that the Retro-Printer module and my PI4 are not communicating correctly. I can provide examples, but it is the same as you described. If I send a test page through cups, it prints perfectly.

This has proved true now with three different computers. It has proven true with a USB direct connection, printing through CUPS, and sending to PDF or TXT. It is just gibberish. I too would appreciate any resolution you can find.

Thanks
Patrick

[RWAP]

Patrick,

There can be various reasons here and we need to get more detail.

1) What configuration are you actually trying to use? Is the computer originally printing to a HP printer or an Epson printer? If a HP printer, have you set the Retro-Printer software to emulate HP rather than Epson?

2) What printer drivers are you running on the computers to print to the Retro-Printer? A lot of Windows drivers seem to ignore the original PCL / Epson printer codes nowadays and print JUST graphics data.

3) We do not know if you need to set /root/config/bit_depth to 7 or 8 (default is 8). A lot of equipment seems to have corrupt data in bit 8, which leads to a host of issues.

- Example raw data files are the best bet first of all so that we can investigate the issue. We actually test these by using a QL emulator running on a Windows PC - printing via a raw / plain text printer driver, using a USB to parallel cable.