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• The Comms Link cometh

  James Fossey • 07/09/2019 at 22:31 • 0 comments

  I've ordered a Comms Link. Well, in fact, it's an original Psion Comms Link with a free Psion Organiser CM included. Yes, that's the right way round - the cable is worth more than the Organiser now! Total cost £22, but I hope to recoup some of that by re-selling the Organiser CM. This is good news for the project, because it means all that fiddling around with machine code and SSCR now won't be necessary. The disadvantage is that the solution won't exactly be compact. Oh well.
  

  
  What exactly is a Comms Link? It's a device that equips a Psion Organiser II with an RS232 plug. They were sold by Psion as a must-have Organiser accessory for the eyewatering sum of £60 in early 1988 - bear in mind the cheapest Organiser II sold for £99 at that time!
  

  (picture of Comms Link from Centre for Computing History)
  See that grey box with 'Comms Link' written on it? In there is a little chip which contains some terminal emulation/file-transfer software for the Psion, imaginatively called COMMS. If I connect the RS232 end to the Pi (via an RS232-to-TTL converter and possibly a 25-9 pin converter) and the other end to the Psion, I should be able to control a Pi terminal session using the Psion. Which is basically the aim of this project.
  

• Is the Psion actually useful in 2019?

  James Fossey • 07/03/2019 at 20:49 • 0 comments

  OK, I admit this project hasn't advanced very much recently as I've had quite a lot of other stuff to be getting on with. But I have been trying to make use of the Psion (in its standard form!) in my everyday life. Is it worth buying a Psion Organiser II for a few pounds off eBay in 2019 - if you don't intend to modify it? Well, here are a few uses for the device.

  
  - It's a good, loud alarm clock. You can set 8 alarms up to a week in advance.
  

  - The database is good for storing small amounts of information for short periods of time. I've used it to note down things like phone numbers and brief 'reminder' notes.
  

  - Psion Tetris (see last log) is good fun for whiling away 10 idle minutes.
  

  - You can buy a selection of Datapaks* containing original 1980s Organiser programs on eBay for £7.50 a pop. Things like word processors, the 'Travel Pack' and the 'Games Pack.' I haven't tried any of these but some of them could still be fun and/or useful.
  

  Of course, if (unlike me) you own a fancy smartphone you can do all of these things at lightning speed in glorious Technicolor. But hey, that's what ordinary people do - and being ordinary is a bit of a waste of time.
  

  As a final note - I have noticed recently that some modern (USB) Psion Comms Links have appeared on eBay for the not inconsiderable sum of £35 + postage. Realistically I think the Comms Link route is the only viable way to get the Psion (sort-of) online, so I am tempted to take the plunge. If I do, rest assured I'll witter on about it here...
  

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  *'Datapak' was Psion's commercial name for a removable storage device for the Organiser. A Datapak is just an EPROM in a plastic case. It was possible to buy blank datapaks of various sizes (I have a 32K and a 16K Datapak) and also 'pre-recorded' datapaks containing commercial programs. They plug neatly into the back of the Organiser.
  

• Talking to the pins

  James Fossey • 06/13/2019 at 19:16 • 0 comments

  The good news: I have managed to physically connect the Pi and Psion. I have also managed to send a simple 'signal' (literally 'pulses' i.e. single bits) from the Psion to the Pi's UART RX pin using SSCR* - but not the other way round. At least, not yet.
  
  It turns out that reading and 'toggling' the pins in the Psion top slot isn't easy! As far as I know there is no simple command in OPL (the Organiser's built-in BASIC-esque high level programming language) that will let me set/read the state of the 3 general-purpose pins in the top slot. It looks like I will need to concoct some simple (?) machine code routines to toggle and read these pins. Until then, I have to stick to Organiser Tetris for my 8-bit entertainment...
  

  
  Reading data from the Pi using SSCR would only be possible if I get hold of an 'official' Psion Organiser Comms Link, or something hardware compatible with this device. The Comms Link was the commercial name of the RS232-based device Psion produced in the '80s to allow the Organiser to communicate with the PCs of the time - back when PCs had serial ports and monochrome monitors. Psion Comms Links still pop up on eBay from time to time but they aren't cheap. A modern USB version has also been produced and sells for 20 Euros plus postage.
  

  For now, though, I'm going to try and do without a Comms Link. Let's delve into the wonderful world of 1980s machine code...

  *pedantic note:  the only pin I can toggle with SSCR is pin 2 on the top slot (SD0) which is not the pin I showed in the table in my last post!
  

• First steps...

  James Fossey • 06/08/2019 at 20:56 • 0 comments

  So this week I've soldered the low-voltage side of the SparkFun converter board 'onto' the Raspberry Pi. I've let four long leads run freely from the high-voltage side of the board that can be pushed into the pins of the Psion top slot (breadboard-style!)
  

  I've put the connections so far into a table. Now I need to put a fresh Raspbian Lite on the Pi and try to work out how to 'use' the Psion top slot. I believe it has 3 general purpose pins that can be read and written to using some kind of machine code. This page is proving very interesting https://www.jaapsch.net/psion/topslot.htm#p16.
  
  

  Pi	Logic level converter (low voltage side)	Logic level converter (high voltage side)	Psion Top Slot
  Pin 1 (3.3V)	Low Voltage reference (LV)	High Voltage reference (HV)	Pin 13 (5V)
  Pin 6 (Ground)	Ground (GND)	Ground (GND)	Pin 9 (Ground)
  Pin 10 (GPIO15)	Low Voltage 1 (LV1)	High Voltage 1 (HV1)	Pin 15 (SOE)? TBC
  Pin 8 (GPIO14)	Low Voltage 4 (LV4)	High Voltage 4 (HV4)	Pin 16 (SMR)? TBC

  
  

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