How to record data from foreign sensors? - Page 2 - RC Groups
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Jun 12, 2009, 10:11 AM
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It looks like you've backed yourself into a corner. There is not a good eageltree solution, and you are short of space in the airborne pod. Here in the US there are many micro development systems available for relatively small amounts of money.
One of them could be programmed to record your data and then later merge it with Eagle Tree's. Space for a second recorder would be an issue.
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Jun 12, 2009, 10:15 AM
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I should have added that if your local electronics department cannot help I can check for you here. It's better to have local help though.
Jun 13, 2009, 10:16 AM
Registered User
Well, that sounds difficult...

With my knowledge about electronics, and with some support from students of electrical engineering, do you think i can make it to get the sensor to elogger?

But i can not ask my prof for making a custom paid project, because the head of the university will not pay more than the module...

For the problems with drift: the honeywell support told me, though i want to place the sensor in a very dynamic behaving environment, i will not have any problems with drifting or wrong records...

What do you think? i have to make a desicion now, because the time will slip through my fingers... i got permission to order the HMC6343. Do you think i can make it, bill?
Jun 13, 2009, 10:22 AM
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dshares, thank you very much for your help. if you have any solutions or options, just tell me...

to all: the compass module can also be placed in the tail of the plane... the problem for any solution is the limited budget. i cannot spend more money. If using an additional data logger and a compass module which has the same abilities like the 6343 is not more than 200, okay. But the time's running, i have to order the material at the very latest next week...
Jun 16, 2009, 02:19 PM
billpa's Avatar
Hi Soulkitchen,

I don't think this is going to work out, especially if you need to have the new sensor supported quickly. Sorry about that!


Bill, for Eagle Tree
Jun 16, 2009, 05:33 PM
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hm... but you told me that i can use any sensor using I2C! I also was told by a colleague, that if i had the necessary commands of the sensor, i can make it.

Bill, can i contact you by phone? when can you be reached (GMT)? just tell me, soulkitchen (at) o2online dot de

Perhaps then we get a solution... =) Thanks!
Jun 18, 2009, 05:52 PM
billpa's Avatar
Hi Soulkitchen,

I would like Eagle Tree to support a compass sensor at some point. As I mentioned, the price point for the one you need is not in the price range of the vast majority of our customers.

Adding support for a new sensor is not a trivial task. The sensor's protocol has to be supported, the data have to be logged, processed, etc.

If we take the significant time to develop support for this sensor, for one customer, it negatively impacts our many customers who are waiting for other sensors and features to be supported, such as Gforce on the eLogger, GPS data compression, etc.

I feel bad about not being able to help you! Sorry about that.


Bill, for Eagle Tree
Jun 18, 2009, 07:01 PM
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Just have one more look at , page 13
i can also order the usb bemo board for programming. can that be helpful? can i get the module to the elogger on my own with this tool?

If not: i need an alternative. is the only alternative using another logger?
Jun 18, 2009, 08:35 PM
Registered User
PAge 13 didn't make a lot of sense to me, but, as an alternative... if, as and when you might want to explore that path... Try googling "arduino and digital compass"... you'll get over 6500 hits. A ready made solution for you might well be among them! Loads of support and huge forums about them. Your EE techs might well be able to assist you modify it to suit, although it's easy enough, and well documented for even a Mech eng. to thrash around until it does what you want. :-) Good luck
Jun 19, 2009, 03:15 AM
Registered User
equusine: the module mentioned there is 2 axes and not tilt compensated.
For "page 13": this is the datasheet of the sensor i want to order. on page 13 you can see also a demo board. with that you can configurate the module.
i think about that: if i knew the commands the elogger uses to communicate with his own sensors, i could exchange the relevant commands in the compass module. making a trojan horse you could say!

Bill: i understand that you can not offer support from eagle tree. But you did not answer my question yet =) Could i do the integration on my own and what do i have to do for it?
Jun 19, 2009, 06:06 AM
Registered User
Hi Soul
Sure, I see what you are saying, but why do you think that makes a difference? As I said; "it's easy enough, and well documented for even a Mech eng. to thrash around until it does what you want." I'm sure you tried HMC6343 and arduino too?

I don't that anyone other than you can answer the question of what you can do or cannot do! :-) But isn't discovery learning one of the happy parts of you doing your thesis?? (unless its a management thesis about Maslow, Herzberg et al! lol)

Last edited by equusine; Jun 19, 2009 at 06:14 AM.
Jun 20, 2009, 12:03 PM
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equusine: the module has do be placed into a plane. that means that the module nearly never is positioned horizontal especially when you make turnings etc. so the north vector is measured wrong! and i cannot make mistakes in a dimension of 20% in the worst case! =) (tilt angle!!!) And for compensation you need 3 axes...
This is also the point why the arduino tools are out...

the hmc6343 will be bought, because after a long research there is no cheaper module available which has the mentioned features.

but i think i have a solution at the moment: after Eagle Tree can not specify the firmware for integration i found another logger which offers everything i want except pressure measuring. i can integrate the Eagle Tree Sensors there and it costs not that much.

Just have a look at [Edited: sorry for the competitor-link, i did not know that this is not allowed. what it was about: datalogger with SD-Card, communitation Rs232, I2C, UART, SPI, ..., free programmable code, about $80. for more information: PM]

they also offered support for integrating my hmc6343 - for free =) and it's open source!

that sounds pretty good, what do you think?
Last edited by Soulkitchen; Jun 21, 2009 at 08:55 AM.
Jun 21, 2009, 06:58 AM
Registered User
Firstly, I think there maybe something in the forum rules about advertising or commending competitors products, you may want to check that and edit accordingly.

I think one of us is missing the point! Let me rephrase my previous point... What difference to the >>output<< do you think it will make?

The calculating of tilt angle are you are talking about is done where?

A. On the board within the chipset?
b. externally after the data leaves the board?
c. In the data logger?
d. Glove?
e. none of the above?

Assume for a moment that the data output from the mag compass is just a 4 digit string. The only difference in that 4 digit string for tilt / non tilt types is going to be the accuracy of that 4 digit number.

What your conclusion assumes is that the tilt calculation is done after the data has left the chip/board! I don't think you are correct.

My assertion is that the programming available to listen to the data coming from a non tilt compass is just as valid in listening to tilt compensated compass as it's the accuracy of the same data, nothing more.

but if you believe you have found the best solution, best of luck.

EOT - click
Jun 21, 2009, 08:14 AM
Registered User
although i don't know if it's allowed to compare other loggers with ETS logger, thank you for the buzz, i corrected that as you can see above to avoid trouble. =)

i understand your point, but you are missing the most important thing. to get a clear correct vector - no matter where it is been calculated - you need 3 (three) sensors, a 3 axis compass module:

- getting the north vector, one axis
- tilt angle to longitudinal axis
- tilt angle to lateral axis

so for a correct compensation you cannot use a 2 axes module

now for calculation:
in general:
you have more opportunities what kind of data you can record:
see page 10

also you can see here that the north vector can be calculated within the module or external. You can choose what format you prefer.

and the last thing: the output is not just 4 digits as you can see on page 10...

for the last thing: tilt compensation and accuracy. imagine the following:

- flying in direction of 270 degree , horizontally, no change of height. everything is measured correctly, north is 90 degrees to the right.
- flying in direction of 270 degree , horizontally, change of height, let's say 45 degrees (for more easy calculating below). everything is measured correctly, because you are turning on the north vector axis.
- flying in direction of 270 degree , tilted 45 degrees on longitudial axis, 45 degrees tiltet on lateral axis (change of height)... where is north? no, not 90 degrees but 150 degrees to the right in flight direction!

error: 66%...

but i agree with you in the point: it is irrelevant where you calculate the compensation: in the module or after recording and getting the 3 sensor signals together.

the hmc offers this option also. it's up to the size of memory, which is very limited using the ETS
Last edited by Soulkitchen; Jun 21, 2009 at 08:58 AM.
Jan 22, 2010, 04:52 AM
Registered User
Any update to this? I also need an OSD that will take data from a 3 axis digital compass and display a heading, are there any EagleTree products that support this?

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