Bit bang Serial port and Xmodem issue

[Derek Cooper]

Hi all,

I have an SC114, by default it uses a bit bang serial port at 9600. It does support Hardware flow control.

It works fine as a terminal, I can upload text to it in the SCM monitor. For example I uploaded, as a hex file, Putsys for CP/M no problem. 

The download.com program seems to work ok, i've only tested small files so far.

However Xmodem is a complete waste of space! It never works. It just sits there and never exits. Sometimes you get lots of re-try packets on the sending PC.

Anything I'm doing wrong? Any suggestions?

Derek

[Bill Shen]

See this discussion about Xmodem with SC114.  It does work with 30K or smaller file.  Binary files will not transfer; it needs a software patch.  The brand of USB-serial seems important.  This reminds me that I’ve ordered and received FT232 USB-serial adapter so I should do more test.
https://groups.google.com/g/retro-comp/c/MB3vODaBSMs/m/hvnggylmAAAJ

Bill

[Derek Cooper]

Thanks Bill for pointing me in the right direction.

I have patched (botched!) the Console driver for bit bang 9600 to remove the issue of the NULL character being used to denote nothing received. 

Re-compile the PutSys hex file and installed it to my SC114

Success, I am now able to use Xmodem transfers for binary files etc exactly the same as the SIO card. I transferred a 200k file that was a ARC file of sc2 and it works fine.

I have attached the patched file for you to try.

I have also attached a version of PutSys, if you want to try it right away!

Have fun

Derek

ps do you think Steve would want this sent as a patch or something?

[Derek Cooper]

Further info,

The stock version of XMODEM.COM still seems to have issues, I suspect it's timing issue with the start frame NAK/ACK

My own version of xmodem, on github here: https://github.com/coopzone-dc/xmodem80

works fine but can take up to 30 seconds to start the transfer, again i think it's the initial NAK/ACK being slow, But this version tries a bit harder and eventually starts.

I find the best transfer package to use is actually Zmodem - because you can select multiple files to send, start the transfer, and all the files are sent, waiting and ready when you come back to the console. I found ZMRX and ZMTX a long time ago (can't recall where from)

If you would like any of the programs mentioned just ask.

Derek

[Steve Cousins]

Hi Derek,

Thanks for the  patched code. I'll look to adding this in the next release. I should have fixed it myself but you know how time goes.

Steve