Hello everyone!

I'm new to this community and I joined here 

to seek help for my project.

I don't have much knowledge about electronics, and nothing about 

chip programming.

I'm trying to get gyroscope and accelerometer data

of the vibration platform. I'm thinking of using APM with

mpu 6000 sensor on board.

The first problem is, that during measurement, the sensor

can not be connected to pc for data logging (platform is moving), so

the data should be logged on board. Is there a way for data logging on board?

The second problem is, that I need very high frequency for data logging

(minimum 1000 Hz). I talked to someone and he said that I2C bus is too slow for that,

and that I should use SPI bus (up to 20 Mb speed by specification)

Is APM capable of logging data through SPI bus at rates higher than 1000 Hz?

Basically my questions are:

What do I need to log gyro and acc data ( plus time stamp) of vibration platform?

What is the maximum rate I can achieve?

I need to know that before I buy anything and start to play with it, so I don't by

something that is not suitable for my project.

Thank you thousand times for any help you can give to me.

Jernej

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There are many purpose built modules and boards for the type of work you describe.

Trying to bodge/adapt APM is probably more effort in the conversion/adaptation than it is worth.

The contrast of I2C vs SPI is valid.

On the other hand, APM is so very cheap (as compared to bona fide instrumentation devices) and the built in data logging is very attractive. Another problem: you would have to work on the code to reduce the filtering and many other functions built into Mission Planner / Tower.

Another consideration is a slightly older cell phone. Many of them have multi-axis accelerometers in them and are well supported with either Apple or Android code.

I say look at existing industrial products and try to find a good used device/system. You may also find cell phone/tablet based sensors that run logging code for sensors.

A sensor and data logger combination is also very common.

It will save you more time and probably ensure more success on your project.

-=Doug

First, thank you for your reply. 

I've been searching for a purpose built thing for a month now

and I haven't find anything that would be small and could log gyro

data at 1000 Hz or higher.

I tried cell phones, but log frequency is too low...

I would be very grateful if you have any idea where to find such a device.

Jernej

It seems you need a specification list first.

We know your required sample rate is >1000 Hz

What is the number of degrees (axis) of freedom you need to measure (1, 2 - horizontal, vertical - for a vibration table?).

If you go the APM/Pixhawk route, the datasheet for the IMU device will be your limiting value.

HERE is a guide to devices that may help you decide.

-=Doug

Thank you for your reply.

Yes, I would need sample rate higher than 1000 Hz,

and at this rate, I would need time, and all 3 axis gyro information.

The problem that I see now (maybe I'm wrong) is not in the speed of IMU sending

data, but in logging this data at that rate.

I'm also looking at the combination of:

https://www.sparkfun.com/products/11028

and

https://www.sparkfun.com/products/12772

but I don't know if this combination would give me what I need.

I also looked at:

https://www.sparkfun.com/products/11055

This board has MPU 6000 sensor, that can send data via SPI (faster)

but there is a question, is it possible to log the data to any device (RAM, SD card...)

as fast as it is sent from the sensor? 

Jernej

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