winstn60
United Kingdom
Asked
— Edited
Resolved by Rich!
I have a problem with the MMA7455 panel in EZ Builder normally EZ Builder connects fine but if I add the 7455 panel it locks up EZ Builder on connecting to the EZ B board and I have to use Windows task manager to shut it down and start again. It has worked for me but only a couple of times
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My leads are around 4" and it had worked on them without any pull ups. From what I can make out the MMA break out board has pull up resistors on it anyway...
You need long leads at least 6 inches for the MMA 7455 to work
Crediting Rich with the fix to see if I can get it to go away
*confused*
I'm struggling with that problem discussed here.
As soon i activate the MAA 7455 (connected with the i2c) Module in the software the EZ-Board and software freezes.
i really want to use the mma7455 but i cant see whats wrong.
the length of the cables are about 7 inc.
any ideas ?
It is a very sensitive piece of equipment and cable lengths are very important, if they aren't right then it simply wont work.
And the EZ-B V4 will hang and freeze up on any I2C error (the manufacturers of the main processor designed it that way).
Keep trimming back that length and retesting is pretty much the option here. As previously stated, mine were about 4 inches long when I was testing out the device on the EZ-B V3.
thats properly it !
i used different power connectors (3,3V and ground from the Ax row).
..now i have shorten the lines to about 2,5 inches but its still freezing the board.
should i use the power pin's of my used SDA/SCL port ?
2x2 10k ohms in parallel.
but nothing different than before. again ez board freezes as soon as i start the i2c maa7455 module in the software.
here is the set-up:
(red = 3.3 V, brown = ground, blue = SCL, green = SDA)
If you have an Iphone you could try the sensor streamer app (was a free download from the apps store) that sends data straight to your PC and gives you an accelerometer for 3 axis. DJ added a panel to ARC for it.
Otherwise try longer wires to the MMA7455
@julius I can see that you are using 3.3V from the ez-b going into the onboard 3.3V regulator, this might be dropping your voltage down far enough to make the sensor communication unstable. (Thanks for the photos, it definitely helps)
its no car.
its a bi-ped. robot and its looking atm like this :
the MAA7455 should go somewhere on the hips.
i have no iphone, but i'll look for something simular for android.
longer cables will be next.
i might soon get me an oscilloscope, so i'll get a closer look to the levels and timing.
@jeremie should i try to "pull up" with 5 V ?
..for that i need to throw in a 7805 for the regulated 5 V
atm I got 6 x 7806 already in it for 6 V, 5 A max for the servos.
so there is :
- 3.3V from board
- 6 V for servos
- 6.6-8.2 V from the batterie
(they get warm at 5 A max, 2 A average when moving.. they got a small heat-sink by now!)
___________________
I read a bit about I2c spec's. this might be interesting:
(en.wikipedia.org/wiki/I%C2%B2C)
- the SDA/SCL levels should be 5V or 3.3V (but it works with something in between) with pull resistors !
the "low level" is under 0.5V.
- the I2c network stops, if a device is not working properly. (so we had that already)
- ....and also by the total bus capacitance of 400 pF, which restricts practical communication distances to a few meters.
I didn't realize (until you sent the pictures) that you were using that style of application board. That board has pull-ups already on it, as well as a linear voltage regulator.
The voltage regulator will drop the voltage from 3.3V that you are supplying it to somewhere around 2.8V that powers the accelerometer. You may need to by pass the regulator.
I have the same boards at the ezrobot shop, I'll try to do a test tonight.
i just got 2 new ones on ebay.. this will take a while. maybe mine is just broken. its produced alright, can't see any loose resistors or something..
If you have a v3 board you could test your MMA7455 with it to see if it is working as the v3 board is less picky about I2C.
I have a late Christmas gift for you, I was able to get the MMA7455 accelerometer board to work reliably with the ez-bv4. Here's how I did it:
1. Used short wires connected from one of the I2C ports on the ez-bv4 to the MMA7455 sensor board
2. Soldered 4.7Kohm pullups from the SDA and SCL lines to 3.3VDC (these are possibly optional since there seems to be pull-ups on the board)
3. Soldered a 1nF ceramic capacitor from SDA to GND
Here's some pictures of my setup:
You may not need to, but I removed the voltage regulator from the board and shorted the voltage input and output pins so I didn't have a voltage drop (through the regulator) when I provided 3.3VDC to the VCC pin.
I will go through this today or on weekend.
were is that nice i2c-connector-plug from ?
thanks again! a nice Christmas!
http://www.ez-robot.com/Shop/AccessoriesDetails.aspx?prevCat=9&productNumber=101
Edit: I forgot to mention that with you current setup you may just need to solder a 1nF cap from SDA to GND on the board and have it work.
i still had a maa7361. now i'm going into the analog inputs with a X,Y and Z signal instead of the i2c line. its way more cables but its doing its job with a tiny bit of code.
thanks for your help anyways! Have a good start into the new year !