I've been trying to get to the bottom of a problem with my device. I can get it to read position and speed without problems, but I can't clear the errors no matter how hard I try.
One of the the errors seem to suggest the Resolver feedback might be causing clipping, but I have checked the inoput to the device and it looks within limits.
Here is my circuit:
R81 and R 88 are 9K1, C69 and C66 are 10pF, R78, 82, 89, 87 are 47K and C67, C68, C65 and C70 are 1nF
Looking across R88 the following is to be seen:
Where purple is one side of the EXC waveform (for reference), blue and yellow are the sin+ sin- centred around 2.5 volts and red is the calculated differential input at 4Vpk-pk. I believe this is with operational limits?
The excitation frequency is set at 4kHz. and goes from 10kHz (default) to 4kHz during configuration so is working as it should.
When I run my configuration code the following is what I see:
The blue and yellow are now on the LOT and DOS pins. so they briefly go high and then low again, never to go High again, but the device reads position and speed happily.
If I look at the error data with the default chip configuration values except the resolution and excitation frequency, it looks like this:
If I try to mess with the configuration values it improves a little but only ends up like this (see my code for the latest values):
I've tried a number of variations of the thresholds (event putting them at max and min and so far have been unable to get this to work. I could really do with some suggestions please.
I've also checked that the hard reset is working correctly:
It seems to hold low for several ms until the 5V is properly established.
Blue is the /reset line and yellow is the 5V supply, purple is the EXC+ output.
I'm using a TMS320F28379D to communicate with the device using an SPI interface at 5MBit at the moment.
The Code can be inspected here:
I'm hoping someone with better knowledge of the chip can spot where I'm going wrong.....