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Topic: Floating point Co-processor question (Read 1 time) previous topic - next topic

gvi70000

Jan 23, 2012, 10:20 pm Last Edit: Jan 23, 2012, 10:22 pm by gvi70000 Reason: 1
Does anyone used the micromega um-FPU v3.1 or 64 (http://micromegacorp.com/products.html), if yes how fast do you get the results form it to arduino (i want to use I2C)?
I'm thinking to use it because it has fast 12bit ADC and also to make floating point calculations (for gps, motors and others)
but i'm afraid that the time gained in the calculations or analog reads will be lost in the communication time with the 328 chip.

Thank you

robtillaart


If you search in the upper right for micromega you find several threads, might be usefull ...
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

Graynomad

Quote
i'm afraid that the time gained in the calculations or analog reads will be lost in the communication time with the 328 chip.

I haven't looked at the numbers but I'd say that would be the case.

There is an SPI version of that chip, that would be 5-10x faster.

______
Rob
Rob Gray aka the GRAYnomad www.robgray.com

retrolefty


Does anyone used the micromega um-FPU v3.1 or 64 (http://micromegacorp.com/products.html), if yes how fast do you get the results form it to arduino (i want to use I2C)?
I'm thinking to use it because it has fast 12bit ADC and also to make floating point calculations (for gps, motors and others)
but i'm afraid that the time gained in the calculations or analog reads will be lost in the communication time with the 328 chip.

Thank you


Well the V3.1 datasheet gives performance speeds for all the instructions starting on pdf page 31. What I don't recall seeing is timing performance of the standard arduino software floating point functions and without that it's hard to estimate the improvement possible. Maybe the datasheet gives some comparisons? :

http://micromegacorp.com/downloads/documentation/uMFPU-V3_1%20Datasheet.pdf

Note the chip also supports SPI communications with an arduino as well as serial and I2C and would be the fastest method I believe. The also have an arduino library to support usage of the chip. If you do get one be sure to let us know how it works out for you.

Lefty

gvi70000

Hi,
thanks for the reply's.
I can't use SPI because i don't have enough pins to use so i will need to use I2C.
I want to use the chip for:

1. Get and process NMEA string from a GPS;
2. Process data from accelerometer, gyroscope and magnetometer;
3. Read two sensors.

At this moment i use FastAnalogRead to improve the speed when reading the sensors(on A1, A2 of arduino), i get the data from GPS
using Rx/Tx and make all the math on arduino (float to long long integer).

From what i've read in the data sheet i can store custom functions in the FPU that will unload loats om math operation from 328.
It can communicate with the GPS and also do the string processing and last but not least it has 2x12bit fast ADC.

I did read the posts from this forum but none answered may questions.

My main concern here is that i will invest extra money on the chip but the speed gain will be lost in the communication time between
arduino and the chip.

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