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Attempting to get serial communication with the C4P again. I have a Win10 PC with a built in serial port (as opposed to USB serial adapter) and am using Putty. I bought two new DB9 to DB25 serial cables, one straight through and one null modem. My bag of random cables I had seemed to only have select pins passing through and the pin mapping was inconsistent.

Putty is set to serial COM1 (which matches device manager's port ID) with 8N2 no flow control.

DB25 of null cable to J9 modem port.

power on, reset, M, then enter this:
On Putty, I finally have it where I can enter characters which echo to the putty/pc screen. all previous attempts have not shown anything in the putty screen. but I do not see anything on the OSI. it seems frozen on the last entry from above.

should this show why I type on the putty/pc on the osi screen? is another reset required on the osi? also, does the osi retain memory when reset?

feel like i'me getting slightly closer.

Hey that looks great!

The program you entered is a simple serial port echo program with no output to OSI screen, so that behavior is expected!
We could enhance it to echo to the OSI screen, but perhaps now that communication is established we can try some more complex programs?
On Reset the OSI screen is cleared, but other data is not erased from OSI memory.

But first,
If the OSI does not need the serial port you are using selected in software after reset, you should be able to RESET, then press M and L . Then any typing of uppercase HEX characters on the PC terminal program should be echoed in the OSI monitor. If not then your OSI does need the port selected before transfer by entering the the code: One trick when uploading is to change the serial port speed to 16x faster! You can do this with the following: (assuming you also need the software port select code) Afterwards your OSI should communicate 16x faster : 300baud->4800baud. (Question: What speed worked for you in Putty currently?)
(Both of the above programs leave you back in the OSI monitor, with no visible indication anything happened.)
[I permanently wired the default serial port I/O to the DB-25 connector on the back of my OSI to avoid having to mess with port selection.]

You may have an easier time using a terminal program that can send and receive files. XMODEM is used with several of the disk utilities to speed data transfer, and pasting text from the windows clipboard can be useful.
I've used Tera Term with good success. You can search for it to download on the official Japanese site, but I've had problems with the site timing out lately. However I have a copy on my web page at
https://osi.marks-lab.com/software/file ... -4.106.exe for TeraTerm with installer or
https://osi.marks-lab.com/software/file ... -4.106.zip for Tera Term archive only.

Once again, connect to your OSI with the COM port, set up Tera Term with the same communications setting used before with putty.
Now you can send files located on your PC or upload text from the clipboard. (After entering port selector code if needed :-/)

Try sending a file such as this Kaleidoscope program (right click on the link to save the ".lod" file).

Once saved to your PC, reset the OSI, press M [enter port selector code if needed] then L, next on the PC on TeraTerm select File/Send File... find "kalideX.lod" (check the binary checkbox) and eventually you should see something like this:



Many of the non-BASIC programs on the Games page can be loaded via this same method on your machine.

Good Luck!

Thanks again, Mark. I got sidetracked. at VCFSE I picked up another C4PMF system from the consignment sale for very, very cheap. it was disassembled and in a box but I was told it was complete. All boards, cases, floppy unit. I have it mostly back together, booting with video and prompt, but I'm having issues getting any keyboard entry to go to monitor. once in a while after repeated keys it will go to monitor, but no further keys are recognized. I figured having a spare would be fun to help learn and troubleshoot side by side. and I'll hopefully have two working systems at the end!

back to the serial comm. Null modem cable, teraterm set to 9600, 8/N/2. slower baud rates would not work. haven't tried faster speeds as I almost fell off my stool when it worked.

Side note: My first modem experience was with our TRS-80 Model 1 with a 300 baud modem on Compuserve. 1200 soon after was amazing. Now I'm on 1gig fiber.

Anyway, this is an amazing accomplishment for me. Only took me a year or so, but I got there.

Hey congratulations!
Once you figure it out and have it working the next time is so much easier (as long as you remember what you did)!

So I have to ask, does the serial port connection you are using on the OSI need to be selected in software after reset or does it just work?
It's been so long since my OSI was stock, I don't know the answer. Also which connector did you end up using? Maybe a picture of the back of the OSI?

If it works at 9600, perhaps it was modified at some point in its past? Anyway at least you got it going! 9600 is a good speed to use for general communication.

Cheers

Null cable to the port away from the power cord. I believe it is the modem port in the manual.

I entered the code you provided first. then reset, then M then L. Just like you said! so it does survive the reset just like you said.

On my second C4P from VCF, I was not getting any keyboard responses. it was kinda fun trying to track this back to the problem. having another working unit may be cheating, but I eliminated the keyboard and the video board. turned out it was a single 7402 or 04 on the CPU board. then everything worked!

I'm using Glitch's RAM replacement boards in both systems for now, but I'm pretty sure my original RAM boards are fine too. Now that I have serial working I can load the RAM test.

I'm going to use beefy small Meanwell supplies in these and store the originals. My new C4P still has the original supply and it runs so hot. I've been using a Meanwell switcher on my project machine during testing and it is one less thing to worry about.

Thank you for all of your help and patience!