Suunto EON and Solution Alpha Computers

Suunto EON/Solution alpha Transfer and Data Protocol

History:

1.0 [10 Feb 98]
- first release
1.1 [14 Feb 98]
- search for [1.1] to find the changes
- Solution alpha added
- default value for owner name added
- meaning of ring-buffer overflow counter changed in the Solution alpha
- changed the calculation feet => meter, because the computers doesn't round.
- last byte in the data block seems always to be $82 at the last dive in the log
- the first byte in the data block seems the be the nitrogen level before the dive (at repetitive dives)
1.2 [14 Oct 99]
- search for [1.2] to find the changes
- checksum of the complete block
- max. depth in header
- current year in header
- metric/nitrox flag in the altitude byte

0. Open Questions / Unknown things

Does more than the 3 bytes for the transmission exist? I checked all letters, but there may be others?!?
Any way to set the time of the EON? I don't think so :-(
Does the EON really has a 3 byte counter for the number of dives? Or is it only 2 bytes and the first byte has a special meaning?
What meanings have the other bytes in the header (32..255 with the exception of the serial number in 244..246)? I think 32..210 are unused, but the other contains constant (they never changed at my EON) data.
[1.2] How does the PC software find out, where the first dive in the log starts? At the moment I get the $82 position from the header and search for next $80 (end of dive), skip the temperature and pressure byte and - viola - the first (oldest) dive.

1. Communication

The protocol uses 1200 8N2, which means 1200 baud with 8 bits, no parity and 2 stop-bits.

2. Transfer

You can send the following data to the EON:

'N' ($4E) followed by 20 bytes, sets the owner name of the EON.
'T' ($54) followed by 1 byte ($14, $1E, $3C, which are 20s, 30s and 60s) sets the data rate for the diving profile. Other values may be possible, so the profile values may be recorded with a 1s to a 255s interval - but they should not be used (information from the developer of the EON)
'P' ($50) The EON sends $901 [1.2] bytes (I call it the P-block) back to the computer.

3. Format of the P-block

The P-block has a $100 byte header and a $800 byte ring-buffer for the profile data. The ring-buffer on a new interface only consists of $FF bytes.

[1.2] The last byte is a checksum:

unsigned char chk = 0x00; for(int i=0; i<0x900; ++i) chk += buf[i];

The header has this format:

offset format testvalue content

0-2 MSB binary $00015E number of dives made with the EON (here: 180; from the EON history). I am not sure, if the upper byte is used (I havn't made 65536 dives yet :-)

3-4 MSB binary $0258 divetime under water in minutes (here: 600; from the EON history)

5-6 MSB binary $3F46 [1.2] max. depth (here: $3F46 / 128.0 = 126.5 feet; from the EON history)

7-8 MSB binary $0100 $900 - this value = offset after the last dive (here: $800)

9 MSB binary $3C current profile interval (here: 60s)

10 MSB binary $18 altitude settings (value / 32 = Altitude, here: $18 / 32 = 0, so A0)
[1.2]:
bit 0: unknown (always = 0?)
bit 1: nitrox
bit 2: unknown (always = 0?)
bit 3: metric
bit 4: air (= EON)

11 MSB binary $60 [1.2] current year - 1900 (here: 96 => 1996)

12..31 ASCII "EON - Markus Fritze " 20 bytes string, that is filled with spaces. Not zero terminated! [1.1] If the owner name is never set, it contains $FF..$FF

32..210 binary $FF unused?

211..243 binary $?? unknown

244..246 BCD $502159 serial number of the EON (here: 502159)

247..255 binary $?? unknown

offset	format	testvalue	content
0-2	MSB binary	$00015E	number of dives made with the EON (here: 180; from the EON history). I am not sure, if the upper byte is used (I havn't made 65536 dives yet :-)
3-4	MSB binary	$0258	divetime under water in minutes (here: 600; from the EON history)
5-6	MSB binary	$3F46	[1.2] max. depth (here: $3F46 / 128.0 = 126.5 feet; from the EON history)
7-8	MSB binary	$0100	$900 - this value = offset after the last dive (here: $800)
9	MSB binary	$3C	current profile interval (here: 60s)
10	MSB binary	$18	altitude settings (value / 32 = Altitude, here: $18 / 32 = 0, so A0) [1.2]: bit 0: unknown (always = 0?) bit 1: nitrox bit 2: unknown (always = 0?) bit 3: metric bit 4: air (= EON)
11	MSB binary	$60	[1.2] current year - 1900 (here: 96 => 1996)
12..31	ASCII		"EON - Markus Fritze " 20 bytes string, that is filled with spaces. Not zero terminated! [1.1] If the owner name is never set, it contains $FF..$FF
32..210	binary	$FF	unused?
211..243	binary	$??	unknown
244..246	BCD	$502159	serial number of the EON (here: 502159)
247..255	binary	$??	unknown

The ring-buffer is a stream of data, which ends at the position, that is marked in the header. At this position the EON starts writing the information from the next dive. If the write pointer reaches the value $900, it jump back to $100.

One dive has this format:

offset format testvalue content

0 MSB binary $?? unknown
[1.2] the first byte in the data block seems the be the nitrogen level before the dive (at repetitive dives)

1 MSB binary $01 repetitive dive counter (here: the first dive). The counter resets to 1, when the EON turns off after a longer pause. Every dive before that is a repetitive dive and increments the counter.

2 MSB binary $3C profile interval for this dive (here: 60s), this is necessary, because the interval may be changed after every dive and the ring-buffer still contains information about dives with other profile intervals.

3 MSB binary $38 altitude settings (value / 32 = Altitude, here: $18 / 32 = 0, so A0)
[1.2]:
bit 0: unknown (always = 0?)
bit 1: nitrox
bit 2: unknown (always = 0?)
bit 3: metric
bit 4: air (= EON)

4 MSB binary $64 [1.1] A solution alpha always transmits a 0.
[1.2] on nitrox: nitrogen level

5 BCD $97 year (here: 1997). Don't know, what happens at year 2000.

6 BCD $01 month (here: 1 = January)

7 BCD $31 day (here: 31)

8 BCD $13 hour (here: 13 or 1pm)

9 BCD $35 minute (here: 35)

10 ... binary profile data

n MSB binary $80 end of the dive

n + 1 MSB binary $3C temperature at the dive in degree celcius - 40 (here: 60 - 40 = 20 degree celcius)

n + 2 MSB binary $19 tank preassure at the end of the dive in bar (here: 25 * 2 = 50bar)
[1.1] A solution alpha always transmits a 0.

n + 3 MSB binary $?? unknown
[1.2] the last byte in the data block seems to be the nitrogen level after the dive?

offset	format	testvalue	content
0	MSB binary	$??	unknown [1.2] the first byte in the data block seems the be the nitrogen level before the dive (at repetitive dives)
1	MSB binary	$01	repetitive dive counter (here: the first dive). The counter resets to 1, when the EON turns off after a longer pause. Every dive before that is a repetitive dive and increments the counter.
2	MSB binary	$3C	profile interval for this dive (here: 60s), this is necessary, because the interval may be changed after every dive and the ring-buffer still contains information about dives with other profile intervals.
3	MSB binary	$38	altitude settings (value / 32 = Altitude, here: $18 / 32 = 0, so A0) [1.2]: bit 0: unknown (always = 0?) bit 1: nitrox bit 2: unknown (always = 0?) bit 3: metric bit 4: air (= EON)
4	MSB binary	$64	[1.1] A solution alpha always transmits a 0. [1.2] on nitrox: nitrogen level
5	BCD	$97	year (here: 1997). Don't know, what happens at year 2000.
6	BCD	$01	month (here: 1 = January)
7	BCD	$31	day (here: 31)
8	BCD	$13	hour (here: 13 or 1pm)
9	BCD	$35	minute (here: 35)
10 ...	binary		profile data
n	MSB binary	$80	end of the dive
n + 1	MSB binary	$3C	temperature at the dive in degree celcius - 40 (here: 60 - 40 = 20 degree celcius)
n + 2	MSB binary	$19	tank preassure at the end of the dive in bar (here: 25 * 2 = 50bar) [1.1] A solution alpha always transmits a 0.
n + 3	MSB binary	$??	unknown [1.2] the last byte in the data block seems to be the nitrogen level after the dive?

The profile data is a stream of bytes. Every minute (or 30s or 20s - see the profile interval) a byte is recorded. This byte is the delta depth to the last depth! E.g. you start your dive at a depth of 0 feet go down to 30ft in a minute, so the value is -30ft (because you go 30ft down) or $E2 in binary, if you then go up to 20ft, the next value will be +10ft (because you go 10ft up) or $0A in binary.

Some values have special meanings:

$7d Surfaced - you have reached the surface while (or after) the dive

$7e ASC - dive now is a decompression dive

$7f ERR - decompression missed? I'm not sure with this value, because I never missed it :-)

$80 End - end of the dive. The next byte is n + 1 in the format description of the dive.

$81 Slow - Slow warning while the dive. If the dive ends with $7d8180 (Surfaced, Slow, End) it means, you finished the dive with a blinking SLOW warning in the display. Bad boy!

$82 End of data - set after the last dive [1.2]

4. necessary Conversions

meter := int(feet * 0.3048 * 10) / 10 psi := bar * 14.50377377 fahrenheit := celcius * 1.8 + 32 [1.2] altitude := 0: 700m, 2300ft 1: 1500m, 5000ft 2: 2400m, 8000ft
ATTN: the computers (checked on the solution alpha) doesn't round after the 2. digit, when calculating feet => meter! They cut it after the 2. digit. This results to the modified formula.

$7d	Surfaced - you have reached the surface while (or after) the dive
$7e	ASC - dive now is a decompression dive
$7f	ERR - decompression missed? I'm not sure with this value, because I never missed it :-)
$80	End - end of the dive. The next byte is n + 1 in the format description of the dive.
$81	Slow - Slow warning while the dive. If the dive ends with $7d8180 (Surfaced, Slow, End) it means, you finished the dive with a blinking SLOW warning in the display. Bad boy!
$82	End of data - set after the last dive [1.2]