Because we want to measure more than just one axis of rotation of our robot this year, we searched out some similar gyros to the one contained in the KoP. The gyro board contained in the KoP is the ADW22307 (data sheet provided by FIRST) and I found the ADXRS622 eval board on Digikey. The specs for this gyro (datasheet) are identical to the provided chip, but the packaging is different (anybody who’s ever worked with the older Analog Devices chips like the ADXRS150EB knows what I mean).
Analog devices says this is a drop-in replacement for the ADXRS612 (datasheet for the 612 eval board). The problem is, it is not a drop-in replacement for any of the older gyro models (such as the ADXRS300).
So, here’s the issue (aka tl;dr): The schematic says we need to provide 5VDC on AVcc, Vdd, and Vratio, which we have done. The ground planes for PGND and AGND are indeed connected, as shown by the multimeter. We get the null voltage out (approx 2.53VDC) of the chip no matter what we do to it. Both 622 chips we have do the same thing. Until we hooked 5VDC to the Vratio pin, we got 0. I asked one of our electrical engineers (I’m a software guy, sorry) to check the schematics and see if I was missing anything. He said he couldn’t see anything. Heck, we even hooked it to a breadboard and wired the pins the same way to see if it was a bad soldering job while wiring up a socket.
We have been measuring the output using LabView, opening the analog port, reading the voltage in a while loop (with a delay built in) and outputting it to a graph. We have also verified it using a multimeter.
I come hat-in-hand to the Chief Delphi community. I have 2 students who I am teaching inertial attitude calculation and tracking to using this project. But we can’t get any measurements out of the gyros.
Thats a stumper, it sounds like you are doing everything I’d do.
Can you verify the connections you don’t have? What I mean is please be sure that you haven’t connected anything to SUMJ, NC, ST[1 2], or CP[1 2 3 4].
Vratio definitely needs to be connected, it is what powers the final output stage of the device.
You can check the KoP Gyro design package at the bottom of this page: http://usfirst.org/roboticsprograms/frc/content.aspx?id=16337 . It is released under a very open license, so do what ever you please with it.
There are also other gyros that some teams have gotten to work, so don’t despair. But before we throw away your parts, lets make this work.
You are correct, we do not have anything connected to the SUMJ, NC, etc other than what they have on the eval board itself. What I haven’t checked is the values for capacitance and all that. I am operating under the assumption that I don’t have two bad chips.
If I could have bought 2 more of what FIRST supplied in the kit, that would have been great. We’ve got some old ADXRS300EB and ADXRS150EB boards (that work, but Vratio doesn’t need to be connected) but the way I understand the rules we can’t use those anymore since they are obsolete and unavailable for purchase. That and having 3 of the same type is advantageous when teaching students about gyro bias and scale factor errors.
<R33> COTS items from ROBOTS entered in previous FIRST competitions or COTS items that are no longer commercially available may be used under the following conditions:
A. The item must be functionally equivalent to the original condition as delivered from the VENDOR (e.g. a part that has non-functional label markings added would be permitted, but a part that has device-specific mounting holes added would be prohibited), and
B. The item must satisfy ALL applicable 2010 FRC materials/parts use rules.
You can still use your old gyros as long as you did not modify them.
Well, that’s good to know.
Well, we never did get the 622’s to work, but I did find a different solution.
We’re using the sensor board from a Wii MotionPlus accessory via I2C for a 3-axis gyro solution, which will go nicely with the I2C readings from the accelerometer board they gave us this year.
I’m sorry to hear the first solution didn’t work, but I’m excited about the WiiMotion Plus solution. Very cool! Let us know how it goes (and then document it so we can do it too).
FWIW: Our team went down the same route using the eval board. I was able to wire it up looking at the schematics referenced in a previous post and matching it with the pin out described in the sheet we received with the board. It seems to work fine for us.
Maybe, its worth giving it another try?