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'ZModem [OT sort of]'
2000\05\15@015644 by uC Novice

picon face
Anyone familar with ZModem?

Here is my situation. I am sending data from a uC via
a serial port to a PC. On the PC, I have Hyperterminal
running in capture mode. I have the baud rate set at
57.6kbps 8-N-1 and hardware flow control. I am
properly taking care of the hardware flow control
lines CTS,RTS,DTR and DSR by looping them back to each
other. I can transmit my data which is HEX and comes
out as ASCII characters on the Hyperterminal window
just fine; however what I really want to do is to use
the "Receive File" mode instead of the "Capture Mode"
because I want my data to be automatically saved as a
file. As opposed to just sitting in the Hyperterminal

When I start the "Receive File" mode in Hyperterminal
it asks me for the protocol...XModem, Kermit, ZModem
etc. I have heard that ZModem is the best but I would
be willing to use any one of them if I could just get
the PC to start receiving my data using one of these
protocols ("Receive File mode"). What happens is that
it times-out like it is waiting for a special byte or
a header before the data. It never starts receiving.

Does anyone know what I need to send the PC in order
for it to start receiving my data using ZModem?
Perhaps it is a special header or couple of bytes
preceding the data that will start it. Again, the
serial port is configured for 57.6kbps 8-N-1 and
hardware flow control and I am using the same hardware
flow-control loopback trick that I used successfully
with the "Capture mode".

Any Hints, Suggestion, or Clues.

The next thing I am going to try is to send a file
with just one ASCII character from one PC to another
using a null modem and this "Receive mode" using
ZModem and probe the data that gets sent.



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2000\05\15@020517 by Plunkett, Dennis


You can use the capture text file for this one, and hyper term will write
the data to your nominated file location. Don't use the X modem style
protocols as you will have to write a handler


> {Original Message removed}

2000\05\15@020726 by William Chops Westfield

face picon face
Xmodem is the simplist of the hyperterm-compatible file upload protocol.
For Xmodem, divide your data into block of 128 bytes each.  For each block
send SOH <blknum> <NOT blknum> <checksum>  Wait for an ACK to be received
before sending the next block, resend the block if you get a NAK.  Terminate
the file by sending just an EOF instead of a new block.

Ymodem adds some filename control and upgrades the checksum to a CRC, and
some versions allow for a larger blocksize.

Zmodem adds sliding windows for full bandwidth utilization.

Basic source code implementing Xmodem sent under separate cover...


2000\05\15@061137 by Bob Ammerman

picon face
ZModem is a rather complex protocol.

XModem is much easier, but typically you would have to enter the desired
file name at the PC end.

{Original Message removed}

2000\05\16@013544 by Nigel Goodwin

In message <>, uC
Novice <.....uc_newbieKILLspamspam@spam@YAHOO.COM> writes
>Does anyone know what I need to send the PC in order
>for it to start receiving my data using ZModem?
>Perhaps it is a special header or couple of bytes
>preceding the data that will start it. Again, the
>serial port is configured for 57.6kbps 8-N-1 and
>hardware flow control and I am using the same hardware
>flow-control loopback trick that I used successfully
>with the "Capture mode".

X-Modem, Z-Modem etc. are packet systems, they send data in packets of a
certain size, X-Modem uses 256 byte packets, and Z-Modem uses 1K
packets, although I seem to recall it can use different sizes?. X-Modem
is quite simple to implement, but Z-Modem is somewhat more difficult,
but in either case I don't think it's what you really need to do.

It would be much easier to write a comms program on the PC to just save
the incoming serial data straight to disk, there's no need to get
involved in complicated packet systems.


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2000\05\16@073750 by briang

In-Reply-To: <>

Nigel Goodwin <EraseMEnigelgspam_OUTspamTakeThisOuTLPILSLEY.CO.UK> wrote:
> X-Modem uses 256 byte packets

No, X-Modem uses 128 byte packets except the X-modem-1K variation which
(obviously) uses 1K packets.

> and Z-Modem uses 1K
Z-modem doesn't really use any particular size, a particular
implementation of Z-modem may use a particular size or it may adjust the
size according to how many transmission errors occur.

X-modem is indeed fairly easy to implement.
I think I have a file about it somewhere I could email to uC Novice if

Brian Gregory.

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