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Get your files mobile with PsiFS 1.4

By Chris Williams. Published: 6th Mar 18:14:15 | Permalink | Printable

Mobile computing today is a very large and rapidly technologically advancing market. However, despite how much storage space your palmtop has you will often need to transfer files and other work to and from your heavy desktop computer. This week has seen the fifth release of PsiFS, a utility that allows RISC OS computers to feed files to and receive files from EPOC or SIBO devices. The transfer of files is handled like an ordinary harddisc filer window; files to be copied can be dragged to and from the PsiFS filer window.

The most significant changes from version 1.30 to 1.40 are

  • SIS files can be installed on EPOC devices by dragging their icon to the PsiFS iconbar icon or double-clicking with the left Alt key pressed. The Add/remove control panel icon is automatically installed if necessary.
  • The interface for third party file format converters has been extended to allow better integration.
  • ARM2 processors (found in older pre-RISC OS 3.5 machines) are now supported.
  • Numerous bug fixes including:

    • Excessively long lines of owner information are now handled correctly.
    • Action windows are no longer automatically closed if an error occurs.
    • Backups can now be performed with the virtual drive option configured.


Drobe spoke to PsiFS author Alexander Thoukydides about his announcement and why he deciced to develop the communication application.
"I bought a Psion Series 5 in March 1998, and wanted to be able to back it up on my RiscPC", explains Alex. Alex tried and considered many existing applications to allow his RiscPC and Psion to talk together. However, in the end he found none of them fully met his personal requirements, including some PC software that he ran on his PC Card.

"Around that time I was also looking for a new project on which to spend some of my free time, having pretty much finished development of both ARMEdit and Virtualise." So after a search around the web Alex found some outline descriptions of the Psion Link Protocol (PLP) as used on Series 3 (SIBO) machines. Encouraged by this, he then digitally momitored the 'handshaking' and flow of data made by the Psion during file transfer to understand how the Psion communicated with other computers: "..with the aid of a serial data analyzer I managed to decode enough of the low level communications protocols to knock together a simple proof-of-concept."

Through a contact at Psion, (now at Symbian), Alex spent a few months piecing together the details of the protocol used by EPOC, the operating system installed in the Psion 5.

"By October 1998 I had the first version of PsiFS up and running that actually worked as a proper file system and allowed files to be written and read. Around that time John Woodthorpe (who runs the excellent http://www.armlink.co.uk/) started to test the software - especially on Series 3 devices that I did not have access to. His feedback and encouragement led to the first public release in March 1999."

Alex spent the next three months fixing the large number of bugs that only show up when the software starts being used on a wide variety of systems, as well as the major function of PsiFS: the ability to perform automatic backups.

"One aspect of the backup system in PsiFS that may surprise some people is that it is performed entirely within operating system callbacks, meaning that backup operations keep going outside the desktop, even while playing single-tasking games. This was relatively easy to implement because that is how the whole of PsiFS operates internally, from the serial communications upwards. It is only the interface to FileSwitch that normally forces foreground-only operation. If RISC OS were to support non-blocking file system operations then it would only require trivial changes within PsiFS to support them.
"Over the last year Gert-Jan de Vos and Thomas Milius both started developing Psion file format converters for RISC OS - the other main omission for connectivity software. Right from the start of developing PsiFS I had decided that I was not going to get involved with writing file conversion software myself, but would provide support for integrating any third party offerings. This I did, and it has resulted in a very versatile and extensible system for adding file converters that can operate transparently as files are dragged to and from applications."

Riscstation, manufacturers of RISC OS computers, have started shipping PsiFS with their rebadged Oregan Scientific Osaris palmtops and as Alex enthuses, "Not bad for a program that started life as a means for me to back up my own Series 5!"


Contacts
Alexander Thoukydides: alex@thouky.co.uk
PsiFS 1.40: www.thouky.co.uk/software/psifs/

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