Accelerometer Usage

dc42

For anyone having problems getting an SPI-connected accelerometer to work:

I have found that capacitive coupling between the SDO and CS signals in the cable can cause a glitch on CS when the accelerometer replied to a read register request, and this glitch stops the accelerometer sending any more data. This is especially likely if those two signals, which use adjacent pins on the Adafruit LIS3DH board, use adjacent conductors in a flat cable. I was able to work around this by putting a 1K resistor in series with SDO at the accelerometer end of the cable.

Ducati87

I'm having an issue with the connection. I used a CAT7 ethernet cable but nothing works. Every time I try to launch the command, the accelerator is not found. Any suggest about which cable I should use? Thankt you.

SIam

@ducati87 I use a USB3 cable and have no problems since then
https://forum.duet3d.com/topic/22878/software-package-3-3beta3-released/68?_=1624809172098

Ducati87

@siam Thank you Slam, I will try it

dc42

@ducati87 said in Accelerometer Usage:

I'm having an issue with the connection. I used a CAT7 ethernet cable but nothing works. Every time I try to launch the command, the accelerator is not found. Any suggest about which cable I should use? Thankt you.

See my reply immediately before your post.

Ducati87

@dc42 what do you mean for "in series with SDO at the accelerometer end of the cable"?

dc42

@ducati87 I mean connect the resistor between the SDO pin of the accelerometer board and the wire that goes to MISO on the Duet, instead of connecting the wire directly to the SDO pin.

Ducati87

@dc42 perfect thank you!

StaticRed

@dc42 i will definetly try that out. I had firstly swap my board because of that early production process. While doing that i also swapped my z axis, now need to reconfigure than, and then can test the lis3dh again.

Ducati87

@dc42 said in Accelerometer Usage:

@ducati87 I mean connect the resistor between the SDO pin of the accelerometer board and the wire that goes to MISO on the Duet, instead of connecting the wire directly to the SDO pin.

in spite of the 1K resistor, the accelerometer is not found. I checked the cable on my duet daughter board and everything seems to be ok. Any suggest? Thank you.

dc42

@ducati87 thanks for trying. I've no more suggestion yet, but I will get back to this when I have time. What sort of cable are you using, and how long is it? Photos of the two ends please.

MikeS

@dc42 i'm in the same situation as @Ducati87 . Here's the thread where i have asked for help and post a photo of the wiring https://forum.duet3d.com/topic/24099/accelerometer-on-duet2wifi-duex5-expansion/3

CCS86

Same boat here.

M955 P0 >>>> "Accelerometer not found"

M955 P0 C"exp.pa22+exp.pa21" >>>> "Accelerometer not found on specified port"

Running RRF3.3 Stable
Wired with a VGA cable. I could probably take about 12" out of the cable length. I left it longer to keep the second ferrite noise filter in place.

dc42

@ccs86 I can't see anything wrong with the wiring or configuration command; so I guess it's an issue of cable length. How long is the cable? A 900mm long multicore cable is working OK for me on a Duet WiFi.

Have you tried temporarily unplugging the PT100 daughter board?

CCS86

@dc42 said in Accelerometer Usage:

@ccs86 I can't see anything wrong with the wiring or configuration command; so I guess it's an issue of cable length. How long is the cable? A 900mm long multicore cable is working OK for me on a Duet WiFi.

Have you tried temporarily unplugging the PT100 daughter board?

I just tried unplugging the daughterboard and still not finding the accelerometer.

I may try re-wiring with a CAT6 cable, if there aren't any other easier steps to take.

Phaedrux

@ccs86 Are you using a Maestro board?

CCS86

@phaedrux said in Accelerometer Usage:

@ccs86 Are you using a Maestro board?

Yes.

Phaedrux

@ccs86 said in Accelerometer Usage:

@phaedrux said in Accelerometer Usage:

@ccs86 Are you using a Maestro board?

Yes.

The lack of floating point unit makes accelerometer usage problematic. I didn't even think there was a build for the Maestro.

dc42

@ccs86 when we are happy with the performance of input shaping on boards that have floating point hardware, we will look at the feasibility of doing a build for the Maestro.

CCS86

@phaedrux said in Accelerometer Usage:

@ccs86 said in Accelerometer Usage:

@phaedrux said in Accelerometer Usage:

@ccs86 Are you using a Maestro board?

Yes.

The lack of floating point unit makes accelerometer usage problematic. I didn't even think there was a build for the Maestro.

It is my understanding that accelerometer usage is okay, with the potential issue being in running input shaper. I'd still like to start measuring with the accelerometer for a baseline and for mechanically trying to improve resonance.

@dc42 Can confirm if that is the case.