Hoppi Mac Application

Table of Contents



Hoppi is an application for Apple macOS to allow communication with HP48/49/50-series calculators using the Kermit file transfer protocol. It supports both USB and RS232 calculator ports.

The application implements a Kermit server and presents a simple interface to the user allowing the state of the connection to be controlled and monitored. A key focus of the app is to allow the entire file transfer process to be controlled by the calculator, hence features are provided to allow the calculator to perform folder and file selection independently of the computer.

In addition, to support the character set used by these calculators (which includes mathematical symbols as well as the usual alphanumeric characters), calculator character codes are mapped automatically to Unicode UTF8 codes on the computer (both file names and file content). The particular mapping used is compatible with that described at Character Map.

Using Hoppi

The Main Window

The Hoppi application main window is shown in the following figure, displaying its state after transferring a file called ``→dB'' from the calculator to the computer.


Figure 1: Hoppi main window

The main window is composed of three main areas:-

  1. across the top of the window is the current workspace folder path,
  2. on the left is the calculator status panel, and
  3. on the right is the Kermit protocol status panel.

The current workspace folder is the folder on the computer from/to which all file transfers will be made. In this case it shows the ``Documents/RPL/'' folder of my home folder. Click on any path component to open a dialog allowing you to choose a new folder. To allow files in this folder to be overwritten by transfers from the calculator tick the ``Allow Overwrite'' checkbox.

The calculator status panel, on the left-hand side of the window, shows the current state of the connection to the calculator. There are two modes of operation: USB or Serial. If USB is selected then Hoppi will attempt to communicate with the calculator via the calculator's USB port, and will show ``calculator detected'' when the calculator is attached and switched on. In this mode it will ignore the serial device choose-box. Alternatively, if Serial is selected, then Hoppi will try to communicate with the calculator's serial port, using the serial device selected in the drop-down choose-box.

Note: serial adaptor cables often connect to the computer via a USB port. However, the combination of cable and driver will appear as a serial device to any applications running on macOS, so to use one of these cables the Serial option should be selected. This applies, in particular, to those special all-in-one cables that connect the computer's USB port to an HP48 serial port. In short, select the option that corresponds to the calculator port that is being used.

The Kermit protocol status panel, on the right-hand side of the window, shows what is happening in the current transfer. In case of problems you can reset the state of the Kermit server by pressing the Reset button.

The Packet Logger Window

The packet logger window, accessible from the View menu, displays the contents of packets as they are sent and received.


Figure 2: Packet logger window

The contents of each packet are displayed on a single line in five fields.

  1. a right-pointing arrow for a packet received from the calculator, a left-pointing arrow for a packet sent to the calculator,
  2. the sequence number of the packet,
  3. the Kermit packet type (denoted by a single letter),
  4. the data contents of the packet (enclosed in hollow brackets), and
  5. the packet checksum (enclosed in hollow brackets).

In addition, ticking the ``Show Hex'' checkbox shows the data and checksum contents of each packet as sequences of hexadecimal byte values on a second line.

The Message Logger Window

As well as transferring files, the Kermit protocol supports the sending and receiving of arbitrary text messages. These are initiated by the sending of special ``X'' packets, as opposed to file transfers which are initiated by ``F'' packets. The message logger window can be used to examine all such Kermit messages, both inbound and outbound.


Figure 3: Message logger window

In addition to these X-packet messages, Hoppi also treats unnamed file transfers as message transfers. That is, file transfers initiated by an F-packet that contains a zero-length filename. In this way it is easy to generate such messages on the calculator using the HSDNO and HSNDS Hoppi RPL Library commands – simply specify an empty string as filename (see the Hoppi RPL Library documentation for details of these commands).

The reason for wanting to be able to send messages from the calculator to the computer is that this is the mechanism by which GROB files are transferred to the GROB viewer window, as described in the next section.

The GROB Viewer Window

The GROB viewer window, accessible from the View menu, allows GROB object messages to be displayed.


Figure 4: GROB viewer window

To send a GROB object from the calculator to the computer, it should be recalled to the stack then sent to the computer with the following command sequence (see Hoppi RPL Library)

  "" HSNDO

this sends the GROB as an unnamed file, which will be intercepted by Hoppi and displayed in the viewer window. See the previous section for details of message transfers in Hoppi.

The image seen in the viewer window can be pasted into other macOS applications by selecting Copy from the Edit menu then pasting into the other application as normal. In particular, the Preview application features a ``New from Clipboard'' feature in the File menu which can be used to export the image to the file format of your choice.

Transferring Files

The calculator SEND, RECV and KGET commands can be used to transfer calculator objects to and from the computer, as they can with any Kermit server.

For example, to send a calculator object stored in global variable PGM1 to the computer, issue the command


on the calculator. And to transfer it back again, storing it in the current calculator directory, do


or possibly instead


followed by invoking ``Send File…'' on the computer (from the File menu) and choosing the ``PGM1'' file in the current workspace folder.

Alternatively, these calculator commands can be invoked in the FILER on an HP49G+/HP50G, or in the ``Transfer'' program on an HP48 calculator (accessible via right-shift I/O on the number 1 key). The latter can also be used to manage the computer's current workspace folder completely from the calculator. Note however that its equivalent on the HP49G+/HP50G has problems with these extended features, and instead the Hoppi RPL Library can be used.

In addition to transferring calculator objects Hoppi can be used to transfer the contents of arbitrary text files to and from the calculator, where they will appear as string objects. To send the contents of a text file to the calculator select the "Send File as String…" function from the File menu, choose the appropriate file, then issue the RECV command on the calculator. This will create a variable in the current calculator directory (named according to the file name) holding a string object corresponding to the contents of the text file.

To send the contents of a string object to the computer as a text file, select the "Receive File as String" function from the File menu then issue the SEND command on the calculator. This will write the contents of the string to a file on the computer, the file being named according to the name of the sent variable on the calculator.

Note that only the very next transfer will be treated as a "text file transfer". Subsequent transfers after this will revert to standard calculator object transfers. This can be seen by noting the the "Receive File as String" menu item will become ticked after first being selected, then become unticked when the transfer has taken place. To cancel a pending text file transfer simply select the "Receive File as String" menu item again and it will become unticked.

This text file transfer can also be achieved, under control of the calculator, using the HGETS command from the Hoppi RPL Library. The reverse process, sending the contents of a string object to a text file on the computer, can be accomplished using the complementary HSNDS command from the library.

Obtaining Hoppi

Downloading a Release

Hoppi is freely available from http://bitbucket.org/cloudycat/hoppi/downloads where you should find versions for PowerPC and Intel Macs. The PowerPC version requires macOS 10.5 (Leopard), the Intel version requires 10.7 (Lion) or better.

Building from Source

Hoppi is an open source program with an MIT-style licence (see the LICENCE file for further details). The easiest way to obtain the source code is to clone the Hoppi version control repository. This is a Mercurial repository hosted at http://bitbucket.org/cloudycat. To clone it to your computer issue the command

hg clone http://bitbucket.org/cloudycat/hoppi

in a Terminal session.

Hoppi is written in Clozure Common Lisp (CCL), an implementation of the Common Lisp language that supports direct interaction with the Objective-C runtime on macOS (see http://ccl.clozure.com for more information). In addition a small C library, libhoppi-io, is used for interfacing with the Mac's IOKit framework. It is called from, and calls back into, the Lisp environment.

To build Hoppi, build the C library first using Xcode and copy the generated libhoppi-io.dylib file to the src/lib/hoppi-io/ directory. Then generate NIB files from the included XIB files (using Interface Builder on older macOS or Xcode on newer). Finally build the application itself from the CCL IDE (see the file app-build.lisp) and install it, like any other app, by copying it to your Applications folder.


For reference, for communication with the HP48 I have used the USB cable sold by eTek-Plus on eBay (http://stores.ebay.com/eTek-Plus), also available from Samson Cables (http://www.samsoncables.com), and I have also used an FTDI US232R-10 USB-serial convertor cable (along with a standard HP48 serial cable).

Known Issues

HP49G+/HP50G Transfer program

Hoppi has been tested with an HP48GX and an HP49G+ calculator where file transfer seems reliable on both. Furthermore, the HP48GX "Transfer" program (accessible via Left-shift I/O) works to its full extent, allowing retrieval of directory listings and remote control of Hoppi's current workspace folder. However, the HP49G+ "Transfer" program (accessible via APPS->I/O functions->Transfer) seems to have some problems using these extended features, sometimes generating nonsensical Kermit packets. It is for this reason that I have developed a simple RPL library/application for file transfer on the HP49G+/HP50G calculators, known also as Hoppi. It is included with the main Hoppi application download and has its own documentation. It is optional, you don't need it to perform basic file transfer, but I find it useful for managing transfers, and it is also HP48G compatible.

Alternatively, you can use the standard built-in SEND, RECV and KGET commands directly (or within the "File Manager" program) on the calculator, possibly also with my HRCD and HRLD RPL commands (see the Hoppi RPL library documentation for details).

macOS 10.5 PowerPC

The Copy menu item for the GROB viewer has been disabled when built with Clozure CL 1.6 on PowerPC, due to a problem with the application crashing. I don't understand why this happens, but hopefully it will not inconvenience too many people.

Version History

Hoppi Mac App Version 1.4

  • Now builds on CCL 1.6 again, so support for PowerPC Macs is back.
  • Hoppi-side transfer timeout is extended to 20 seconds to ensure very large objects can be transferred to the calculator (the kermit implementation on HP48 calculators slows down as the transfer progresses).
  • Updating in the GUI of the number of bytes sent is now performed on a per-packet basis, instead of in 1024 byte bursts.

Hoppi Mac App Version 1.3.4

  • Now builds with Clozure CL 1.11 and so works on macOS Sierra (10.12). Will not build with versions of CCL below 1.11, so will no longer build on PowerPC Macs.

Hoppi Mac App Version 1.3.3

  • Fixed handling of Kermit "F" generic command (G packet, F command).

Hoppi Mac App Version 1.3.2

  • Fixed handling of file and folder names containing a semicolon.

Hoppi Mac App Version 1.3.1

  • Corrected location of libhoppi-io.dylib in the application bundle. Now works on OSX 10.10.3.

Hoppi Mac App Version 1.3

  • Added the message logger window.
  • Added the GROB viewer window.

Hoppi Mac App Version 1.2

  • Added the ability to send and receive text files as calculator strings.
  • Included the Hoppi RPL Library version 0.4.
  • Improved documentation.

Hoppi Mac App Version 1.1

  • Now automatically re-opens last successfully opened serial device.
  • Added support for Kermit's generic C and D commands.
  • Added HRCD and HRLD UserRPL utility commands.
  • Corrected handling of single-character directory names.

Hoppi Mac App Version 1.0

  • Initial stable version.


Finally, why is it called Hoppi? Take the capital letters from "HP Packet I/O" and rearrange them. Plus it sounds frog-like (for Kermit). Well, I didn't say it was profound…

Author: Paul Onions

Created: 2017-01-19 Thu 19:44

Emacs 24.5.1 (Org mode 8.2.10)