XR crashes at 122 packets

[mengstr]

No description provided.

[billk2112]

It always fails for me on 121 packets. It works excellent other than that . I can’t get kerm411 to work reliably and this looked perfect until I tried the larger files.
Using a Tom’s Z80 SNC.

[mengstr]

Oh... I've all but forgotten about this project. It's a strange bug that is triggered by such an odd number as 121/122, but now when I think about it again it strikes me that it might be caused by a stack overflow. Let me see if I can find the cause and fix it.

[billk2112]

It might be a symptom of a larger problem with my system. I have the same thing happen with Kermit411 and also when I use The utility download.com. No method that I can send data to my SBC works on files above a certain size.

…

On Apr 15, 2019, at 4:08 AM, SmallRoomLabs ***@***.***> wrote: Oh... I've all but forgotten about this project. It's a strange bug that is triggered by such an odd number as 121/122, but now when I think about it again it strikes me that it might be caused by a stack overflow. Let me see if I can find the cause and fix it. — You are receiving this because you commented. Reply to this email directly, view it on GitHub, or mute the thread.

[SvenMb]

Same here, it fails on block 122 ...

Btw. I found XMODEM 2.7 by M. Eberhard in a patched version to use CON for the RC2014, that one works well...

[coopzone-dc]

Hello, I have a similar issue at block 122, using minicom (on linux host) sending to cpm2.2 running on esp8266 (one of your other projects) Minicom says Retry 0, got 0d for sector ACK

[coopzone-dc]

FIXED; you need "pop HL" after the djnz line in GetRestOfPacket; like this:

Note the line that says ADD THIS:
GetRestOfPacket:
push BC
ld A,1
call GetCharTmo
pop BC

    pop     HL              ; Save the received char into the...
    ld      (HL),A          ; ...packet buffer and...
    inc     HL              ; ...point to the next location
    push    HL

    djnz    GetRestOfPacket

    pop     HL              ;ADD THIS
    ld      HL,packet+3     ; Calculate checksum from 128 bytes of data
    ld      B,128
    ld      A,0

........
without this pop you get a stack overflow.

Also the error handling and exit routenes are not really right, for example two lines use jp BDOS - i would normally expect that to be a CALL not JP. Having said that these don't stop it working.

I did fix these parts as well, but as i say - they don't stop it working. If i only new how to contact the author or hoe to upload to github - i would!

Coopzone

[gd-99]

@coopzone, thanks for the bug fix, solved my problem as well. Scanning the source, I thought it looked like there could be some additional error checking. It is possible to upload a zip file here. Any chance of uploading a zip file of your corrected XR.ASM and XS.ASM sources here?

GD

[coopzone-dc]

Hello, I don't have permissions on this original Github site, but I have cloned this repo and amended the files there. You can find them here: https://github.com/coopzone-dc/xmodem80

[gd-99]

Thanks, will head over there now...

[cbrock487]

FIXED; you need "pop HL" after the djnz line in GetRestOfPacket; like this:

Note the line that says ADD THIS: GetRestOfPacket: push BC ld A,1 call GetCharTmo pop BC

    pop     HL              ; Save the received char into the...
    ld      (HL),A          ; ...packet buffer and...
    inc     HL              ; ...point to the next location
    push    HL

    djnz    GetRestOfPacket

    pop     HL              ;ADD THIS
    ld      HL,packet+3     ; Calculate checksum from 128 bytes of data
    ld      B,128
    ld      A,0

........ without this pop you get a stack overflow.

Also the error handling and exit routenes are not really right, for example two lines use jp BDOS - i would normally expect that to be a CALL not JP. Having said that these don't stop it working.

I did fix these parts as well, but as i say - they don't stop it working. If i only new how to contact the author or hoe to upload to github - i would!

Coopzone

I experienced the same crash. Always when the received file exceeded 8K in size. That was the size of my stack at crash time. My fix was nearly the same. All I did was move the PUSH HL that was immediately above GetRestofPacket to just below it. In other words, inside the loop. I use XR to download files into my homebuilt eZ80 MP/M II computer. I coded XR into a Process (it can still be made into a .COM application). I also added a prompt to capture filenames from the user. It got a bit tedious to type in filenames in the source file and re-assemble each time.