How to Install/Setup PC to HP41CL Serial Transfer Software?


Hi all,

I recently decided to refurbish a HP41CV that was given to me & to convert it to a HP41CL using Monte's new board. Also decided to include the optional serial connector as an alternative the HP-IL PIL-BOX I use with my other HP41s.

Am expecting the new board & other bits & pieces to arrive within the next week or so but in the meantime I've been trying to setup Raymond Wiker's .NET programs but I must be missing something as I can't seem to get the CL Reader or Writer to work. What I have done so far is to save the Reader & Writer source files as .cs in my computer's C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319 folder then created shortcuts to csc.exe in this folder with: csc.exe /t:exe CLWriter.cs in the target. But when I launch the shortcut all that happens is a command box briefly appears/disappears. Suspect I am "miles" away from the required setup procedure so would appreciate any suggestions or more detailed advice on how to set these programs up.

I run Windows 7x64 operating system but can also run a virtual PC in Windows XPx32 mode if that is required.

Many thanks,



Hi Michael, you must run this program in the Dos command box.


I think you're making this more difficult than it needs to be :-)

What you should do is to save the source files (CLReader.cs and CLWriter.cs) to the directory that you want to run the utilities from, open a CMD prompt, chdir to the directory that you saved from, and run csc from there. That should give you CLReader.exe and CLWriter.exe, in that directory. After that, you can move the exe files if you want to.

So, if you have a directory c:\CLStuff, the sequence of operations is

1) Copy CLReader.cs and CLWriter.cs to this directory

2) Open a CMD window

3) In the command window, type

    cd /d C:\CLStuff
C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\csc.exe /t:exe CLReader.cs
C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\csc.exe /t:exe CLWriter.cs

You should then have CLReader.exe and CLWriter.exe in the directory C:\CLStuff


Many thanks Raymond & John. Will give your instructions a go later this week.




Hi Raymond,

I just tried your installation instructions & received the following error in the CMD prompt: "CLReader.cs(3,17): error CS0234: The type or namespace name 'Ports' does not exist in the namespace 'System.IO' (are you missing an assembly reference?)".

Is there anything else I need to do before running the compiler or have I missed anything? Presume the original instructions are also suitable for Windows 7 x 64?

Many thanks,



Hmmm... odd. I don't think the Windows version should make any difference, but what I think I know may not be relevant :-)

Do you have any better luck with compiling CLWriter.cs? Where did you get the files from?

You could try using one of the other .NET versions; if that doesn't work, you could try removing the second line (or commenting it out) --- that's the line that says

using System.IO;

Sorry I cannot be more specific - I'm on holiday, which means I'm unlikely to be near a Windows machine for some time :-)


Thanks Raymond for taking the time to respond during your holidays :-(.

Tried CLWriter.cs & unfortunately received the same error.

I obtained your files from Monte Dalrymple's 41CL web site. Are these the latest version?

Will try your suggestions later today & let you know how I go. Could also try to compile the programs on a Windows XP machine I have but then I guess the executables will not work on my Windows 7 machine.

Hope you enjoy your holidays.




I tried a few things & found .NET V3.5 compiled the necessary executables without error. Maybe the CS files are not fully compatibe with V4.0.30319 in Windows 7.

Am awaiting for the CL board to arrive so didn't have a 41CL connected to my computer but when I run the CLReader & CLWriter they also just flash-up momentarily. Is this what should be happening as I was expecting to be able to select the serial port etc?

Are there any instructions available on how to use the CLReader & CLWriter to transfer data between the PC & 41CL?

Many thanks,


Edited: 8 Aug 2012, 5:53 a.m.


Are you running the utilities from the Windows Explorer? If so, any information printed out will flash by too quickly for you to see. You also will not be able to supply an parameters.

If you run the utilities from a Cmd prompt, without any parameters, you'll get a description of the command syntax. You'll probably have to experiment a little to find the fastest setting that works reliably for you.


Hi Raymond,

Yes I was trying to run the utilities from Windows Explorer. After so many years without using DOS it is no longer instinctive for me to start with the CMD prompt :-(.

CLReader & Writer run fine from the CMD prompt & I can see the descriptions you indicated. As I understand from the comments that appeared, I need to launch CLReader or Writer as follows to transfer files:

CLReader.exe filename port# [Baudrate]

Is that correct or do I have enclose the file name in " "? Also, I presume the files have to be located in the same directory as CLReader & Writer?

Many thanks,



I think it'll be more reliable with a delay break at the end of the command line. Try 2 or even 5... it works flawlessly for me, even at relatively high baud rates.

for example:

clwriter clutlsb1.rom com5 4800 2

and yes, the rom files should be in the same directory.

Edited: 12 Aug 2012, 6:25 p.m.


Many thanks Angel.

My HP41CL board should arrive at my home in Australia within the next couple of days & I look forward to trying your instructions after I convert my spare 41CV.

I presume when you refer to rom files that you mean any file at all including programs?




Hi Michael, Raymond's program is for ROM image files transfer - this is what I use it for so far. The serial link is capable of sending single bytes back and forth but you'd need to write a driver routine to control things, and on each side I imagine.



Thanks again Angel.

Do use the ROM image files to install additional modules in your calculator that are not already available in flash memory or for other purposes? Also, during serial transfer via Raymond's programs, do I need to XEQ in particular sequence of compands on the calculator itself as you would with HP-IL?

Have started going through Monte's manual & your 41CL Extensions ROM user manual but haven't come across these things yet.

Sorry for the simplistic questions but my 41CL journey is just beginning :-).




If I recall correctly there's an appendix in the CLUTILS manual with Raymond's instructions on how to use his program. Basically you need to prepare the CL to receive/send the data, then trigger the action on both sides.

If sending to the CL, you'd use YIMP on the CL and then CLWRITE on the DOS prompt. Have it ready so there's not time outs.

If receiving from the CL, you'd use CLREAD on the DOS prompt and then YEXP on the CL.

On either case you need to initiate and configure things, using SERINI, BAUDxx on the CL and the appropriate command line switches.

It's really simpler than it sounds.



Hi Angel,

Found the appendix you refer to in your user's manual (Appendix 5) that explains Raymond's instructions.



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