RS232 NO CONNECTION

[Marco Rey y Sander]

Hello lovers of old "computers"!,

I bought the PAL-1 and yesterday "soldered together". It worked right away. I am still a novice. I also have here the KIM Uno. Here the connection with a terminal works wonderfully. If I want to establish a connection with the PAL-1, it does not work. I have tried several cables (which work with various other computers). I also have a USB to TTL here. The following connection I have set (looking at the port on it): 2 and 3 for data communication, 5 for GRD. When I set the PAL-1 to reset, it shows in the terminal that a "byte" was transferred. After pressing the Enter key nothing happens. Pressing the other keys on the PAL-1 does not transfer any bytes. Any helpful tips?

beste regards

Marco

[Hendrik-Jan Megens]

Hi Marco,

great to see you here, welcome!

For me the PAL-1 was my first 'big soldering project'. I had some issues too connecting. I'm now connecting with 4800 baud and that seems stable enough. Anything higher and it seems flaky. The KIM-UNO is a modern board by all accounts - it can handle just about any baud rate. I've found the PAL-1 quite different in interfacing, loading software, etc, but that of course is really the fun.

Also note that you need to close jumper 1 or else you won't get a serial connection at all. Btw, I'm not an expert by any account, so if none of this works just keep posting, there are some here that I'm sure can get you through any issue you may have!

Cheers,

Hendrik-Jan

[Marco Rey y Sander]

Hi Hendrik-Jan,

thanks for the welcome!!! I actually came to the subject of assembling hardware very late. But it makes me very much fun and I also understand more and more! I have set the jumper. I have also made various settings in the terminal program (the KIM-1 manual says to set the stop bit to 2, for example). Unfortunately everything without success. Which cable do you use? Maybe I will buy one again.

Best thanks and best regards from Germany

Marco

[liuga...@gmail.com]

Hello Marco,

Maybe the baud rate is too high, you can try the baud rate from 1200 (8/n/1) to see if it can connected.

The other thing you need check is the RX and TX pin. The PAL-1 need a RS232 extend cable, common RS232 to USB cable is the null-modem cable. If you cannot get connection with 1200 baud rate, you can try exchange the rx and tx pin then try again.

Thanks!
Liu

> --
> You received this message because you are subscribed to the Google
> Groups "PAL 6502 computer" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to pal6502+u...@googlegroups.com
> <mailto:pal6502+u...@googlegroups.com>.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/pal6502/9bda3eac-57e1-4e4f-b0da-85df70ad7913n%40googlegroups.com
> <https://groups.google.com/d/msgid/pal6502/9bda3eac-57e1-4e4f-b0da-85df70ad7913n%40googlegroups.com?utm_medium=email&utm_source=footer>.
> For more options, visit https://groups.google.com/d/optout
> <https://groups.google.com/d/optout>.
>

[Neil Andretti]

Good morning Marco,

I use  a standard serial cable (no 0modem) and a gender changer to connect it.

This worked right away with my main PC (but not with another one I tried)

Baudrate 2400 is fine, jim has an instruction on his page to finetune the rate on the PAL https://github.com/w4jbm/PAL-1-6502-SBC

The USB-serial converters did not work for me in first, I ordered about 3 util I found a working one.

Number three is stable.

I also use a TTL-serial converter to attatch the PAL-1 to a PiZero, but the converter I bought was crossed and made me a lot of headaches, and a dirtyhack to make it work:

https://netzherpes.de/blog/index.php?entry=A-Graphics-Card-for-my-KIM-1-Clone (at the end you see the malheur)

[Hendrik-Jan Megens]

I have the same experience - sometimes serial adapters don't work. I stay away from the cheaper ones you can buy at AliXpress but even then no guarantees (this is not even specific to PAL-1 - once I have a working serial adapter cable for any one of my projects I keep that setup together).

The one I currently use with my PAL-1 is this one:

UGREEN USB to RS232 Serial Cable USB Serial DB9 with PL2303 Chipset (2M) UGRE... https://www.amazon.de/dp/B00QUZY4WO/ref=cm_sw_r_tw_dp_QVVVPKF81YBYA997MEJB?_encoding=UTF8&psc=1

I use a gender changer since this adapter and PAL-1 out are both male. Null modem conversion shouldn't be necessary. 

If you still have no luck, do a thorough check with a magnifying glass for cold joints - all my previous problems of stuff not working were related to me being too careful not to overheat the components. I've since bought a new soldering iron, one that has temperature control (and I actually now have a FAR higher soldering temp than before!). If you see a cold joint, you can always reflow. I also check everything for shorts due to inadvertent solder bridges.

I also always check any cap, resistor, diode, or transistor using a cheap component tester before inserting. But Liu is using very high quality components so I wouldn't expect them to be faulty. (actually, to be honest, I've never found a non-working component in any of the kits I've ever bought for any board).

Good luck,

Hendrik-Jan

[Marco Rey y Sander]

Thank you all for your answers! I will try to bring the port alive!!! 😊👍

[Hans Otten]

make sure you have a rs232 cable, and not a ttl cable. rs232 cables 

have 9 pin connectors, you also need a gender changer. 

1200 baud is reliable, try that first,above ove if you are lucky. 

[bdamours]

Hi everyone,

I got exactly the same problem; my PAL1 run well as standalone, but can't connect to a terminal.  I have obviously set everything according to the guide (and tried those from the MicroKIM guide), and some variations, down to 600 bauds.  I also use a USB to serial adapter, that is recognized by the PC and Tera Term, and a gender changer for connection.  When probing with a scope, I can see signals sent to the PAL when typing on the PC's keyboard (pin 3 on the serial connector), but I see nothing when PAL should answer (pin 2), except the drop in voltage when I hit Reset on PAL's keyboard.  That makes me think the problem is either something in the send circuit, or the USB to Serial adapter.  

I try to track she signals from U2C and U6B (on the schematic) but I see nothing on the Pal's side of R35, I need to play with the scope settings...   Any advice on what I should check now?  

Thank you,

Benoit

[Neil Andretti]

Hey Benoit,

If you have the chance, try to use a real com port. As said, the USB Serial adapters are not identical, and depending on the used chip simply not working.

Nils

[bdamours]

I have ordered the same UGREEN USB to serial adapter than Hendrik-Jan used successfully, we'll see...

[Liu GN]

Greetings Benoit,

The R35 on PAL-1 is the receive pin of RS232, I think you can try swap the RX and TX wire between PAL-1 and USB to serial adapter to see if it works.

Thank you,

Liu

--

You received this message because you are subscribed to the Google Groups "PAL 6502 computer" group.

To unsubscribe from this group and stop receiving emails from it, send an email to pal6502+u...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/pal6502/080e942c-d849-4dde-a138-0144ab36b2f2n%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[Marco Rey y Sander]

Me too, lets try it ;)

[Marco Rey y Sander]

Hi,

i ordered this cable: UGREEN USB to RS232 Serial Cable USB Serial DB9 with PL2303

The cable was delivered today. I have a connection 😊

best regards

Marco

[Hendrik-Jan Megens]

Hi Marco, that's great! What baud rate are you using? 

[Marco Rey y Sander]

I have made a short check with 1200,8,None,1> I will prove more tomorrow!

[bdamours]

Hi everyone,

Update with the  "UGREEN USB to RS232 Serial Cable USB Serial DB9 with PL2303", it worked for me too (i just tried 1200 bauds for now).  I have also successfully tested reading and saving papertape format files.  A suggestion to Liu: maybe you could add a list USB to serial adapter that worked for others, so people could buy a working one right from the start...

best regards,

Benoit

[Hendrik-Jan Megens]

Hi Benoit,

great to see things are working! Regarding working adapters: it REALLY is hit or miss. So I'm afraid your recommendation to Liu is very difficult for him to follow up. I've had cheap adapters that worked, others that only worked for some of my builds. And even then, you can't be sure. 

I actually bought another UGREEN adapter, since my earlier recommendation post here reminded me that I needed one for a new project. It turned out that this new one that I got last week - listed as EXACTLY the same one that I bought a few years ago, didn't work with one of my older Ubuntu systems. Turns out in the mean time the chipset changed, and for this Linux box I had to modprobe that driver manually to the kernel. My newer Linux installs are fine, the driver apparently found without problem.

So, based on this experience I'm glad my recommendation worked out for you, BUT given the chipset changed in the mean time this is a bit of a lucky outcome. 

Cheers,

Hendrik-Jan

[GN L]

Hi Benoit, 

glad to hear your RS232 works!

and Thanks Hendrik-Jan, in theory, all USB to RS232 cable will work if the cable can be normally operation on your (host) computer. 

The key component of a USB to RS232 cable is the driver chip, the cable I use is a UGREEN cable (CR104 sales in China) powered by Prolific's PL2303 chip. I tried this cable on Windows 7, 10, Mac and a Debian laptop, all platform can works.

The common problem using RS232 on PAL-1 is most converter cable default to null-modem pinout, but PAL-1 needs an EXTENSION pinout cable to connection, because the RX, TX are interchanged on the PAL-1 PCB, so the converter cable usually need an cross link converter (such as a gender converter with crossed RX, TX pin). If some cable cannot work with PAL-1 but can works with other device, I think the pinout needs to be check first.

Thanks,

Liu

[Jim McClanahan]

For a lot of my projects, I've had good luck with the TTL serial "cards" with USB jacks on them. Most of them will plug into a header strip and just need a USB cable with a mini or micro connector on one end. I've picked up the ones with mini connectors for around $2 each when buying a dozen or so. I try to get ones with at least TX and RX LEDs on them. Since it eliminates the need for the MAX232 type level adapter (and the space they take) it's probably cheaper than including a serial port. The downside is if you have a real "dumb terminal" you want to connect to you have to hunt down or build a card that gives you a true serial port.

This is the route I take on most of my projects.

Ironically, the only serial port problems I've had are on my vintage Dell laptop where the serial port only puts out +/-3.3 volts and some of my older computers need at least around +/-4 volts or so.

Jim W4JBM