MMA7455 Interfacing with PIC18F

[Nirajrk]

Hi,
I am planning to interface MMA7455 Accelrometer module with PIC18F4520. Please help me with connections.

How the signal transmission should be done if the MMA7455 is mounted separately from the PCB ? Would it need RS232 or I can work with I2C ?

 

[tpetar]

Use I2C or SPI interface.

Connections can be done over pin header, wires,...


MMA7455L ±2g/±4g/±8g Three Axis Low-g Digital Output Accelerometer
**broken link removed**


Best regards,
Peter

 

[Nirajrk]

Thanks Peter..that was quick

the reason I am doubtful is, I'm afraid the signal accuracy would be lost or something if I transmit it over longer distance. Is it true? How long is advisable?

 

[milind.a.kulkarni]

One can make an interface with accelerometer with PIC18F4520- but couple of things there before you start .....
1) define the purpose of using your accelerometer ...... and
2) state that correctly to seek for the proper feedback

The chip MMA7455 gives output in SPI interface(Fast speed digital interface ) i2C (low speed digital interface) rightly pointed out by 'Tpetar' (One of the most experienced Expert on edaboard ....basically I am the big fan of his answers) which is digital interface.

Your doubt is right - SPI or I2C interface are generally implement on board.... but when you say longer distance .... please specify it in the 1-10 meter....likewise...... better option is store the data locally and go for traditional methods of communication like RS-232 or 485 even RJ45 ( network method) or wireless options like RF or Zigbee methods based on your application spectrum demand.

I will still go with RS232 interface to be implemented in micro-controller as it give good/Fast debug facility if it is lab based demonstration.

I hope this will give you some direction.

'Teptar' - would you like to add any more things ?

Good Luck

 

[tpetar]

Hi my friend milind.a.kulkarni,

Nirajrk what is distance between sensor and other part of circuit, I suppose uC ?

If you have long distance between, better do something suggested by Milind.a.kulkarni.





Best regards,
Peter

 

[Nirajrk]

Thanks again Peter & Milind.

The distance between uC & module would be less than 3 meter. The reason I have to mount the accelerometer separately is space constraints. RS232 would increase the cost, size & circuit complexity so I was just trying to explore other options.

Thanks & regards,
Niraj

 

[tpetar]

You can use I2C or SPI two wires, for 3m there is no problem.



Best regards,
Peter

 

[Nirajrk]

Ok will try it out share my experience..thanks

 

[Nirajrk]

Hi...being new to the forum i mistakenly wrote a pm to Milind..here's his last message to me:


"sorry for late response..... but I think i need bit more clarity in the requirement .... like size/space constraints that you said.... as I know micro-controller and and it's varaition can be possible with sensor network chip in 10x10 mm dimension..... I am not sure that your dimensions are less than that, then also sampling speed , sensitivity etc. for any of such comments....

Please make this post public and let's brain strom this based on the requirement that you have

with regards,

milind
***************

The accelerometer module will be mounted on a solid rod of diameter 10-12 mm. I want to sense one particular position of this rod i.e. vertical. The uC that I'm using is PIC18F series & from somewhere I came to know that I2C or SPI won't serve the purpose and I'll have to use serial communication. So I thought of brainstorming on this forum.
And btw I am yet to try out peter's suggestion due to certain other necessary engagements. But will surely do so asap.

 

[milind.a.kulkarni]

As per my understanding about the problem I think this should be doable with wired approach so As teptar suggested you can do wired connection of SPI and power for your sensor and get SPI driver up and running in uC circuit will solve you problem.....two thing I am not sure 1) how do you generate such 'g' grad acceleration and 2) you need do make sure that wires don't get break in your test.....

good luck