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Important Note

MacBS2 will not run on Mac OS X 10.7 (Lion) or later.

MacBS2 uses a software library provided by Parallax to compile your source code to something a BS2 chip can run. This library (called the 'Tokenizer' by Parallax) is available as a PowerPC library only, so linking to it requires the application (MacBS2) to be PowerPC as well.

There is no PowerPC support on Lion, and Parallax have not upgraded their library since 2004. So we are out of luck for the time being.

If you'd like to see a MacBS2 that runs on Mac OSX 10.7 (Lion), give Parallax a shout through their support page and let them know that a native library for Intel based Macs is important to you. Once an upgraded library is available, I can do the rest.

Frequently asked questions. And answers.

Q: It seems that MacBS2 is having trouble communicating consistently with my USBBOE or through my FTDI based USB-Serial converter. Any suggestions?

A: First make sure you're using the latest version of MacBS2.

Some recent versions of FTDI's driver for the FTDI chip (which is what the USBBOE uses) have some problems. On PowerPC based Macs, I've had good luck with an older version of the driver which can be downloaded here. The very latest version of the FTDI driver seems to work as well.

If you're using an Intel based Mac, you should download the latest very latest version of the FTDI driver.

You'll need to remove the FTDI driver you already have. It's located in /System/Library/Extensions/ and is named FTDIUSBSerialDriver.kext. Just drag it to the trash and reboot, then re-install either the older version of the driver or the newest.

Q: Does MacBS2 work with Parallax' new BS2px?

A: Not at this time. If you'd like to be notified when BS2px support is available, send me an email.

Q: When I try to add a directive:

'{$STAMP BS2P, filename1.bsp,....}

at the top of my main code file, MacBS2 gives me a "duplicate directive" error. What's the problem?

A: In order to make it as easy as possible for inexperienced users, MacBS2 manages the directive line for the user, so no manual editing of the directive should be necessary. In fact, MacBS2 always includes its own directive but hides it from view, that is why you'll get a "duplicate directive error" when you try to add yor own. Making the directive invisible was perhaps not the best design decision and I will be revisiting it in a future version of MacBS2. In the meantime, let MacBS2 manage the directive for you and all will be well.

Q: Does MacBS2 support PBASIC 2.5?

A: Yes, as of version 1.4d1. MacBS2 version 2.0 has even more complete support for PBASIC 2.5.

Q: Does MacBS2 support the DEBUGIN command?

A: Yes and no. While MacBS2 1.4 and later properly compiles code containing the the DEBUGIN command, you will need to use a different program (such as the venerable ZTerm, or, if you're on Mac OS X 10.3 or newer, goSerial works nicely) to do two-way communication using DEBUGIN.

Note that if you do use a different program to communicate with the Stamp over its progamming port, you can run into conflicts since both programs (MacBS2 and your communications program) will be trying to use the same serial port. The solution is not to have both running at the same time.

Q: Is there a list of USB to Serial adapters that can be used with MacBS2?

A: The table below, though not exhaustive, lists some of the adapters I've tried and the results.

Adapter/Board Compatible  
Keyspan USA-19, USA-19Q, USA-19Qi, etc.


Requires driver version 1.4 or newer.

driver page
Keyspan USA28, USA-28x, etc


Requires driver version 1.4 or newer.

driver page
Parallax USB-Board of Education

yes (but see this FAQ)

Parallax' USB Board of Education uses FTDI's FT232 USB to Serial chipset.

Adapters based on FTDI's FT232 chipset

(Easysync, others)

yes (but see this FAQ)

Adapters based on Prolific PL2303 chipset

(Prolific, IOGear, iConcepts, Sakar, Acroname, others)

yes, finally!

These adapters have the advantage that they are usually very inexpensive. But the manufacturer's drivers did not appear to support setting and clearing of the Tx line, which is required by the STAMP programming protocol.

However, there is an Open Source driver for interfaces based on the PL2303 chipset that does work (I tested it on my PowerPC based PowerBook; I don't know if it'll work on Intel based machines). Download the driver from its SourceForge page. Thanks to Guy Umbright for the heads up on this.

driver page


Q: I keep getting the "Basic Stamp 2 detected but not responding. Check power." message when I try to ID the Stamp chip even though I'm sure the power is connected.

A: This happens when one of the signal lines is not connected correctly, most frequently, due to an attempt to use a "PDA adapter cable" to connect the Keyspan adapter to a circuit board. This will not work. You're best off building your own cable (see the wiring diagrams in MacBS2) or trying a crossover cable.

See this if you're using a USB to serial adapter that is not known to work.

Q: Keyspan stopped making the USA-19. They now have a USA-19(something or other). Will MacBS2 work with this serial adapter?

A: Yes, MacBS2 should work with any of the Keyspan USA-19 or USA-28 family of serial adapters. Make sure you have the latest version of the Keyspan drivers, available here.

Q: Can I use a serial adapter built using the FTDI chipset instead of the Keyspan models listed?

A: Evidently, yes. See Ben Lennard's page on the subject.

Note also that the EasySync US232B/LC - Laptop Companion uses the FTDI chips and evidently works with MacBS2.

Q: Can I use some other brand of serial adapter instead of the Keyspan models listed?

A: Possibly, if the adapter's driver presents itself to Mac OS X as the proper kind of serial port. You can check this by launching the Terminal application and typing

ls /dev/cu*

then hit the return key. This will generate a list of devices that MacBS2 can access. You will likely see at least


which is the built-in modem and can't be used for Stamp programming. If your adapter is also listed, it will look something like


If you don't see an entry that corresponds to your adapter then MacBS2 will definitely NOT work with it.

Q: I'm using a non-Keyspan serial adapter and have verified that it shows up in /dev as a cu device, but I still can't get MacBS2 to recognize it. What gives?

A: Make sure you enable the "Show All Available Serial Ports" setting in MacBS2's preferences window, and give it a whirl.

Q: I'm trying to use a non-Keyspan serial adapter and MacBS2 lists it in the list of available ports, but I am getting a "Stamp detcted but not responding" error. Thoughts?

A: Make sure you enable the "Show All Available Serial Ports" setting in MacBS2's preferences window, and give it a whirl.

Q: Does MacBS2 support multiple program slots?

A: Yes! Version 2 and newer of MacBS2 supports multi-slot programming.

Q: Does MacBS2 have a memory map feature?

A: No, but it's on the list of "things to do".

Q: Is MacBS2 compatible with Mac OS 9?

A: No, MacBS2 works only on Mac OS X 10.2.8 or newer.

Q: For some reason, MacBS2 is not able to automatically install the tokenizer. How can I install it manually?

A: Note that you need administration privileges to automatically or manually install the tokenizer. If you have administration privileges and the autoinstall is still not working, please send an email to the feedback address.

Q: I'm working behind a firewall which won't allow MacBS2 to automatically download the BASIC Stamp Reference. How can I manually install it?

A: First, you'll need to get (somehow) the BASIC Stamp Reference itself. It is a PDF file and can be downloaded from http://www.parallax.com/dl/docs/prod/stamps/BasicStampMan.pdf

Once you have the command reference, put it in /Library/Application Support/MacBS2. This will allow MacBS2 to make the command reference available to all users of your Mac.

If you don't have administration privileges, you can put the reference in /User/<your home directory name here>/Library/Application Support/MacBS2, but note that in this case, MacBS2 can only make the command reference available to you.

Q: Can I be a beta tester for MacBS2?

A: You already are.

Q: Do you accept donations for MacBS2?

A: No. But you can buy me something from my Amazon.com wishlist.

My Amazon.com Wish List

Q: Open source?

A: No.

Q: How do I get my question answered?

A: Ask it.