Suunto Solution/Alpha/Eon PC Interface - DIY

Updated 1-12-2004

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Please note that this page describes an interface for the above computer range only.
I do not have access to, or knowledge of Vypers, Cobras or any of the new generation of computers. Please DO NOT e-mail me about them.
The Solution' interface is incompatible with newer units.

However, some clever continentals have produced a site that describes a DIY VYPER interface.
AND, not to be outdone, a British version of VYPER interface.
And yet another for the Cobra

This page contains GIF images of the circuit diagram for the Solution interface, the PCB artwork, the board layout, a typical side elevation of the assembly, a parts list, some hints and a little about troubleshooting.

The Windows "Dive Manager" software is freely available from the Suunto site:

This is a self-extracting 2.5MB file; although Solution variants aren't listed, the same software is used for all the older computer types (just use the Vyper version!). Logbook data created with the old "DiveLog" software can be imported into it.

The schematic diagram is shown below.
The pin numbers for the serial port are for a 9 pin "D" connector as is usually fitted to COM1 on most PCs. They must not be used with a 25 pin connector, refer to your PC's handbook for the functionally equivalent pin numbers, alternatively 9 pin to 25 pin converters are readily available from RS, Maplin and Tandy.

The pcb image is viewed from the copper side of the board to enable those without access to a laser printer to copy the pattern onto copper-clad board with an etch resist pen.
Grid marks are the industry standard 0.1 inch (2.54 mm).

Component layout is shown below.

The stacks of pcb pillars are sleeved with soft rubber tubing so as to support the Solution by the recesses next to the wrist strap.
The diameter of the pillars used on the prototype prevented the Suunto being attached to the interface without first removing the protective plastic screen; by using smaller diameter pillars it may be possible to leave the cover in position.
"Harwin" type spring loaded concave test pins (from RS Components, about 90p each) were used to contact the Solution.
Ignore the board outline and cut the board to suit the box you intend to use. You may need to profile the sides of the board to avoid the pcb guides inside the box.
All component holes are 0.8mm, those for the test pins and pillars should be suitable for whatever parts you use. 1.5mm holes were drilled "above" the cable terminations, the individual wires were passed through these to provide some degree of strain relief for the solder joints.

My prototype was mounted in a small plastic box approximately 100mm x 70mm x 40mm.

A representation of the cross-section is shown here.
Please note that I built mine into a second-hand box that didn't have a lid, I had to fabricate one from a piece of aluminium. The mechanical fittings (pillars/grommets etc.) were all "liberated" from the scrap bin at work.
I assume that most people attempting this project will be able to adapt whatever they have available to suit.

The parts list below should only be used as a guide to what's needed - I didn't acquire the parts for my prototypes from Maplin but I've quoted them as a supplier because they've a UK-wide network of shops as well as a website for on-line ordering and they sell to the general public unlike RS and Farnell.
The stock numbers were taken from the Maplin Professional catalogue - and I assume they'll be readily available from the shops.
None of the component types or tolerances are critical, capacitors may be electrolytic, tantalum or whatever - but do observe the polarity.

Warning, the transistor and the integrated circuit can be damaged by static discharges, never handle them by the leads unless taking proper anti-static precautions and do not allow them to overheat when soldering them into the board (this applies to the diodes also).

** I've been told that Maplin have discontinued the DS14C88, until I can check out suitable equivalents etc. this can be got from RS Components, stock no: 633-521 @ £0.552 (I believe the public can buy at trade counters).
Alternatively, it can be got by mail order from, CPC on 01772 654455, their stock no: SCDS14C88N @ £0.65. Note; It MUST be a low power CMOS device, the standard DS14888 draws too much power from the supplies.

If assembling as per the above images, pcb stand-offs of the type used aren't available from Maplin, however M4 studding (NC25C @ 70p/mtr) suitably sleeved with insulation and fastened through grommets (JX65V @ 47p/10) with M4 nuts should achieve the same purpose.

Maplin's catalogue can be found at:

And for mail order, CPC Ltd can supply most parts however I haven't cross referenced stock numbers:

General assembly views are shown below.

ADDENDUM
I've had reports of the interface sometimes not working with laptop computers which have low power serial ports.

This is probably due to lack of drive voltage from the COM port as the unit derives its power from the spare signal pins.
If desired, you can try powering the unit from two PP3 batteries as shown here. They can be connected via series diodes so that if the batteries are left off, there will be no danger of shorting out the supplies - provided they're kept away from the PLAN, MODE and COM pins!.

1N4148 diodes should work, although BAT42 schottky diodes have a much lower forward voltage drop and should produce a slightly higher supply voltage.
I haven't tried this personally but have been assured that it works.

For those who may have doubts about their PC's COM port levels, Reinhard Kopka has a site with a similar design that uses a MAX232E. This only requires a single 5 volt supply and it may solve some of the problems experienced with laptop computers, however, with this device, all the supply power will be drawn from the positive excursions of the signal pins and this might create extra problems - I haven't tried it so I can't say for certain.
The site is in German, but the schematic is easily understood, the relevant page is at:

It's also been reported that increasing the value of R1 to 1M0 is a simple fix to erratic operation with laptops - certainly worth a try!

Another concern is that almost all new laptops don't have RS232 ports, only USB.
The solution (no pun intended) is a USB-to-serial adaptor. Whilst I can't guarantee all makes will work, I do know that the £5 cheapy I bought from E-Buyer certainly works (unbranded, but the Taiwanese website for new drivers includes the name "Prolific").
Similar devices are sold by CPC for £15, Maplin for £30 and RS for £39!

TROUBLESHOOTING
Hopefully you won't need this section, but if you've built it and it doesn't appear to work, here's a few tips.

First, put it and all the diagrams away for 24 hours and don't think about it. The next day you'll be refreshed, and ready to start again - it's amazing how obvious mistakes are overlooked when you're tired and frustrated. Then, check ALL the wiring, joints, diode & capacitor polarities and component values.

A common problem, with older PCs, can occur when say, a mouse is connected to COM1 and the interface to COM2.
Attempting to "Test" the ports from Dive Manager can result in the mouse pointer "freezing" as COM1 is scanned, the only way to recover is to re-boot the PC.
An easy solution is to manually "tell" Dive Manager that the interface is on COM2 (with the "radio buttons") and not to use the "Test" facility.

A new problem may then arise;
Because the COM port has not been activated by the test sequence, the supply voltages within the interface (in particular the positive supply) may not have been established, this results in all three interface pins being at the same potential which is the same condition as shorting all three together i.e. the Suunto reset condition.
So, if you'd set the Suunto to transfer mode and fitted it to the interface, the Suunto would immediately reset (beep and revert to surface/plan mode) and a transfer would be impossible.
The solution? (no pun intended);
Initiate a transfer without the Suunto fitted to the interface (you may need to set the COM delay to a higher setting), this will cause the COM port to activate and the supplies to be established. Then, set the Suunto to transfer mode, fit it to the interface and initiate a transfer.

Is your COM port working?
If the software doesn't detect the port through the interface, either the interface or the COM port could be faulty.
To test the COM port, you'll need a loopback plug. To make one, simply link pins 2 & 3 on a suitable "D" connector and plug it into the PCs COM port (after removing the interface).
Then, perform the Dive Manager interface test. If the COM port is OK, Dive Manager will think there's a working interface connected to the COM port. This will allow you to get Dive Manager into the transfer mode (see below) and you'll be able to monitor the data levels on an oscilloscope, yes, I'm afraid so, a 'scope is really the only way to fault-find from now on.

All the following voltages are those obtained on my own PC & interface, other PCs may not produce the same voltages.
N.B. The supplies for the DS14C88 may not be present when the interface is first plugged into the COM port. They will only be generated after the COM port has been activated by the Dive Manager software.

Interface Testing (from Dive Manager)
With the interface plugged into the COM port but WITHOUT the Suunto connected:
Perform the interface test from Dive Manager again - but do not short the MODE & PLAN pins.
The MODE pin will be at an indeterminate level (mine is about +7V), it's not critical - but if it's within a few hundred millivolts of one of the supplies, it's possible that the DS14C88 is faulty.
The PLAN pin will initially be at about +3V and momentarily pulse low to 0V as the COM port is scanned.
If this is OK, short the MODE & PLAN pins and repeat the above test, the voltage at the MODE/PLAN junction should initially be about +3V and momentarily pulse low to 0V then return to +3V.

Basically, if Dive Manager recognises that an interface is connected, transfers should be possible and the following should be unnecessary.

During Transfer:
With an interface that has been recognised by Dive Manager OR after "fooling" Dive Manager into thinking there's a working interface connected (with the loopback plug - above):
Pin 3 (Din) will initially be negative (-13V) then pulse high (+12V) then return negative.
The PLAN pin will initially be positive (about +3V) and will pulse low to 0V at the start of transfer, returning to 3V while the transfer is taking place.
Pin 2 (Dout) switches positive (+8V) and negative (-10V) - these levels will depend on the supplies to the DS14C88 (on mine the supplies are +9.5V and -10.5V).
The MODE pin will initially be high (about +3.8V) and during transfer will alternate between +0.8V and +3.8V.

It's more than likely that the DS14C88 isn't switching because its input is being offset by the bias from R1. This can be remedied by changing the value of R1.....
If Dout is always low (negative voltage), try increasing R1.
If Dout is always high, reduce R1 - but not too much, it's important that the voltage on the MODE and PLAN pins doesn't go too high - you may damage the Suunto if this happens.

Finally, If the PLAN pin is always high (positive), try increasing the value of R4 or try a different type of MOSFET (transistor).

CREDITS
My thanks to:
Matthias Aust for the original schematic diagram.
Alison Chippindale for allowing me to play with her digital camera.
Iain Smith for highlighting errors on earlier versions of this page.
Dave Shields for the tip about R1.

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Contact: Dave Cordes.