topic Re: Re: FXAS2100 not going into 'active' state in Sensors

FXAS2100 not going into 'active' state

jimmiller — Tue, 03 Feb 2026 21:57:32 GMT

I am using the FRDM-FXS-MULTI-B board to evaluate and prototype a product with a Parallax propellor MCU.

I have the FXOS8700CQ working and responding so the i2c code is solid.

I can read all of the registers on the FXAS21000 gyroscope and the boot complete flag does go to 1 after a hard reset.

The problem I am having is that I can not set the 'Active' or 'Ready' bits in CTRL_REG1. I can set other higher bits in that register but for some reason bits 0 & 1 do not toggle. When I set the ST (self test) bit, the data does not output as described in the cdocumentation.

Help?

Thanks in advance,

Jim-

Re: FXAS2100 not going into 'active' state

TomasVaverka — Mon, 01 Sep 2014 12:09:50 GMT

Hi Jim,

It is hard to say where the problem might be, I am able to set both Active and Ready bits individually or simultaneously as you can see on the following screenshots.

Writing 0x03 to the CTRL_REG1 register:

Reading 0x03 from the CTRL_REG1 register:

Could you please post here similar screenshots illustrating both I²C write and read operations with the CTRL_REG1 (0x13) register? It might be also useful to see your source code.

How does the output data change when you set the ST bit? Note that the self-test is not factory trimmed, so it is considered successful if the minimum magnitude of change (50 counts for all axes) is achieved.

Regards,

Tomas

PS: If my answer helps to solve your question, please mark it as "Correct" or “Helpful”. Thank you.

Re: FXAS2100 not going into 'active' state

jimmiller — Tue, 02 Sep 2014 18:07:15 GMT

I Can send you logic captures when I get back to lab tomorrow. I'm doubting its the code though, it works for other registers, even the configuration register with the 'active' bit. I can also set low order bits on other registers.

Per your question, the output does not change when I set the ST bit. I was thinking it can only output data when 'active' but that was an assumption.

I Ordered another FRDM board to compare, it seems like a hardware issue so when the new board arrives I can compare results.

who do I contact about supply Of this chip? DiGiKey tried to special order it for me and said they cant get it? We want to go into production in a few weeks, possibly sooner.

thanks,

jim-

Re: Re: FXAS2100 not going into 'active' state

TomasVaverka — Wed, 03 Sep 2014 08:41:45 GMT

Hi Jim,

Actually the FXAS21000 and particularly the PFXAS21000CQR is no longer manufactured and was removed from the portfolio. This product has been only available as a pre-production sample and on certain demo boards.

The FXAS21002 is an improved version of the FXAS21000. In the attached file you can find a basic comparison between these two versions including availability information. As you can notice, samples are expected to be available during this month. You can discuss sampling and the production timing directly with Dan Sadler, who is the product line manager for gyroscopes. There is also the AN4917 describing both hardware and software compatibility.

As for the self-test, you are right that it only works in Active mode, my question was irrelevant in this case.

Regards,

Tomas

Re: Re: FXAS2100 not going into 'active' state

jimmiller — Wed, 03 Sep 2014 16:35:44 GMT

Ok, sent email to Dan, thanks for that.

Below are the logic analyzer captures of the Write and subsequent read of register $13.

Re: FXAS2100 not going into 'active' state

jimmiller — Sat, 06 Sep 2014 02:37:24 GMT

OK, new board arrived and gyro works. Has a bad gyro.

THanks for responding.