Editing Psion Series 5mx

{{Infobox computer
| name         = Psion Series 5mx
| image        = [[File:Psion Series 5mx.jpg|250px]]
| caption      = Two Series 5mx palmtops, one open and one closed
| developer    = Psion PLC
| manufacturer = Psion PLC
| type         = Clamshell palmtop / PDA
| release_date = 1999
| cpu          = ARM710T core in Psion's custom "Windermere" SoC @ 36 MHz
| memory       = 8 MB or 16 MB RAM
| storage      = Internal RAM disk; CompactFlash slot
| display      = 640 × 240 touch-sensitive backlit LCD, 16 greyscales
| sound        = Speaker and microphone, with a dictaphone function
| dimensions   = 170 mm × 90 mm × 23 mm
| weight       = 354 g including batteries
| os           = EPOC (ER5), later renamed Symbian OS
| predecessor  = [[Psion Series 5]]
| model        = Also sold as the Ericsson MC218
}}
The '''Psion Series 5mx''' is the 1999 development of the [[Psion Series 5]], and for many people the high point of the whole Psion line: a genuinely pocketable clamshell with a touch-typeable keyboard, a 640 × 240 greyscale touchscreen, a proper multitasking 32-bit operating system, and ten to twenty hours of use from two AA cells.

Its defining mechanical feature is the '''sliding keyboard clamshell''' designed by Martin Riddiford of Therefore Design and protected by European patent '''EP 0766166B1''': opening the lid slides the keyboard forward, counterbalancing the display and bracing it so that pressing the touchscreen does not tip the machine over.<ref name="wp">[https://en.wikipedia.org/wiki/Psion_Series_5 "Psion Series 5"], Wikipedia. Source for the model history, the patent and designer of the sliding clamshell, the display and keyboard specifications, the physical dimensions, the Ericsson MC218 rebadge, the 5mx Pro, the absence of a Series 4, and the statement that Series 5 and 5mx internals are not interchangeable.</ref>

'''The Series 5 and the Series 5mx look almost identical, but their mainboards, screens and other internal components are different and not interchangeable.'''<ref name="wp" /> That includes the screen ribbon cable — the part most likely to need replacing.

== Hardware ==

=== Processor and memory ===

The 5mx is built around '''"Windermere"''', a custom system-on-chip Psion had made for it, containing an '''ARM710T''' core running at '''36 MHz'''. The earlier Series 5 used an off-the-shelf '''Cirrus Logic CL-PS7110''' with an ARM710a core at 18 MHz.<ref name="wuffs">Ash Wolf (Ninji), [https://wuffs.org/blog/building-a-psion-emulator "\"16 Shades of Grey\" — Building a Psion/EPOC32 Emulator"], 27 December 2019. Source for the Windermere SoC and ARM710T identification, the CL-PS7110 in the Series 5, the ETNA controller, the 5mx hardware variant ID, the boot sequence, the 128-byte PROM contents and read method, the SPI/ADC channel identifiers, the digitiser calibration structure and defaults, the EPOC hardware component names, and the keyboard scanning arrangement.</ref>

The distinction matters: the '''T''' in ARM710T means the core supports Thumb and has different coprocessor 15 behaviour — one reason 5mx and Series 5 software and system images are not simply interchangeable.<ref name="wuffs" />

RAM is '''8 MB or 16 MB'''. The operating system lives in ROM and user storage is a RAM disk, which is why the backup cell matters so much.

=== ETNA ===

'''ETNA''' is a bespoke Psion chip, present on both the Series 5 and the 5mx, that handles the '''CompactFlash and PCMCIA interface'''. It is essentially undocumented — even the Psion Linux developers who were given official documentation had nothing on it, and the OpenPsion code is full of constants captured from working machines.<ref name="wuffs" /> For repair purposes the practical consequence is simple: '''a CompactFlash fault that is not the door switch, the connector or the card is not a component-level repair.'''

=== The PROM ===

The 5mx carries a small '''128-byte serial PROM''' holding its serial number, its factory digitiser calibration and its real-time clock calibration. EPOC reads it by bit-banging GPIO pins and ETNA registers, sixty-four 16-bit words at a time, and validates it with an XOR checksum.<ref name="wuffs" />

This explains a repair-relevant behaviour: '''digitiser calibration is stored in two places'''. The factory values live in the PROM; the user's own calibration is stored in non-volatile memory and '''is lost if the machine loses all power'''.<ref name="s5sm">''Psion Series 5 Service Manual'', Psion Computers PLC, November 1997. Hosted on this wiki as [[:File:Psion Series 5 Service Manual (November 1997).pdf]]. Source for the circuit description, the keyboard and LCD/digitiser interfaces, the LCD power sequencing requirement, the reset behaviour, the exploded views and part numbers, the disassembly and reassembly procedure, the standby current figures and the Final Test fail codes. Written for the Series 5; the 5mx shares the mechanical platform but not the electronics.</ref><ref name="wuffs" />

=== Display and digitiser ===

The panel is a '''640 × 240 passive-matrix LCD, normally-white''', with a separate '''resistive digitiser''' laid over it: a glass lower plate and a hardened plastic top plate, both printed with resistive ink, held apart by very small moulded bumps, with four connections sensing resistance across the X and Y axes. Each connects to the mainboard by a '''22-way flat flexible cable'''.<ref name="s5sm" />

The LCD needs its supply rails '''enabled and disabled in a defined sequence''' so that no residual DC is ever left across the panel — DC causes the liquid crystal to drift and eventually damages its polarisation permanently.<ref name="s5sm" /> That is why the machine re-initialises the display on every power-up, and why a half-powered machine can show odd artefacts.

The screen coordinate origin (0,0) is the '''top left of the LCD, not of the digitiser''', so the silkscreened shortcut icons down the left-hand edge have negative X coordinates.<ref name="wuffs" />

=== Keyboard ===

The keyboard is a '''separate switch matrix assembly that slides out as the screen is opened''', connected to the mainboard by a '''22-way flat flexible cable in a 22-way ZIF connector''' — of which only 20 ways carry keys. The two outside pins are '''grounded to give the keyboard membrane a ground ring for ESD protection'''.<ref name="s5sm" /> Key pitch is '''12.5 mm''', which is what makes the machine genuinely touch-typeable.<ref name="wp" />

Scanning is by column: the OS writes to a KSCAN register to select a column, and reads the rows from GPIO port A.<ref name="wuffs" />

=== What EPOC calls the hardware ===

The operating system reports its own component names, which occasionally confuse people reading the Machine Info screen:<ref name="wuffs" />

* Screen — '''LCD'''
* Power supply — '''APM 500'''
* Keyboard — '''LAP 53'''

=== Analogue measurements ===

Battery voltages and digitiser position are read through an ADC over SPI. The 5mx exposes four channels:<ref name="wuffs" />

{| class="wikitable styled-table" style="width:70%; text-align:left;"
|+'''5mx SPI/ADC channels'''<ref name="wuffs" />
! Channel !! Identifier
|-
| Digitiser Y || <code>0x9093</code>
|-
| Digitiser X || <code>0xD0D3</code>
|-
| Main battery || <code>0xA4A4</code>
|-
| Backup battery || <code>0xE4E4</code>
|}

== Power ==

The 5mx runs from '''two AA cells''', typically giving 10–20 hours of use, with a '''lithium coin cell backup''' to preserve the RAM disk while the main cells are changed.<ref name="wp" />

'''The user reset switch is part of the backup battery's negative contact''', reachable only by opening the backup battery cover and pressing it with a pointed instrument. Operating it vectors the CPU to a warm restart, and user data should survive.<ref name="s5sm" /> A '''power-on (cold) reset''' is generated automatically by a voltage detector when the supply crosses a threshold, and it '''erases everything held in volatile storage'''.<ref name="s5sm" />

'''Removing both the main cells and the backup cell without external power connected will erase the internal memory.'''<ref name="s5sm" />

== Variants and relatives ==

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''The 5mx and its close relatives'''<ref name="wuffs" /><ref name="wp" />
! Machine !! Differences
|-
| '''[[Psion Series 5]]''' (1997) || CL-PS7110 / ARM710a at 18 MHz, 4 or 8 MB. Same case design, '''different mainboard, screen and screen ribbon'''
|-
| '''Psion Series 5mx Pro''' || As the 5mx, but the operating system is loaded from a <code>Sys$rom.bin</code> file on CompactFlash rather than baked into ROM, so it can be upgraded
|-
| '''Ericsson MC218''' || A rebadged Series 5mx
|-
| '''Psion Revo / Revo Plus''' || Smaller, 480 × 160 screen, rechargeable cells, no backlight and no CompactFlash slot; reportedly also Windermere-based
|}

There was never a '''Series 4''' — Psion skipped the number over concerns about tetraphobia in Asian markets.<ref name="wp" />

== Software ==

The 5mx runs '''EPOC release 5 (ER5)''', the operating system that was later renamed '''Symbian OS'''. Bundled applications include a word processor, spreadsheet, database, agenda, contacts, email, a calculator, the '''OPL''' programming language, a Java virtual machine and the STNC HitchHiker browser; the Executive Edition added Opera 3.62.<ref name="wp" />

The '''OpenPsion''' project (formerly PsiLinux) supports Linux on the 5mx.<ref name="wp" /> For working on a machine you cannot switch on, the '''WindEmu''' emulator and the MAME <code>psion5</code> driver both emulate the 5mx accurately enough to be useful for checking behaviour.<ref name="wuffs" />

== Documentation on this wiki ==

* '''[[:File:Psion Series 5 Service Manual (November 1997).pdf|Psion Series 5 Service Manual]]''' — Psion's own 46-page service manual. It covers the '''Series 5''', but the 5mx uses the same mechanical platform, so the exploded views, part numbers, disassembly procedure and reassembly cautions all apply. The electronics sections do not.

== General maintenance ==
{{Main|Psion Series 5mx General Maintenance}}

Batteries, the CompactFlash and battery doors, the stylus catch, the case switch and the flat flexible cables are the routine concerns. See the [[Psion Series 5mx General Maintenance]] guide.

== Troubleshooting ==
{{Main|Psion Series 5mx Troubleshooting Guide}}

Two faults dominate: '''horizontal lines on the display''' from a cracked screen ribbon, and a '''broken hinge-wire hook''' in the chassis. Both are documented, and both are fixable. See the [[Psion Series 5mx Troubleshooting Guide]].

== Hinge and chassis repair ==
{{Main|Psion Series 5mx Hinge Repair}}

The plastic hooks that retain the spring hinge wires go brittle and break. A replacement inner chassis can now be 3D printed. See the [[Psion Series 5mx Hinge Repair]] guide.

== Capacitors ==
{{Main|Psion Series 5mx Capacitor Replacement Guide}}

The 5mx is '''not''' a recap candidate, and it is worth understanding why before opening one. See the [[Psion Series 5mx Capacitor Replacement Guide]].

== See also ==

* [[Psion Series 5]] — the 1997 original
* [[Psion Organiser II]] — where Psion started
* [[Battery Refurbishment]]

== References ==

<references />

{{Navbox-Psion}}

[[Category:Psion]]