7i85s startup question
- Doug Crews
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14 Sep 2023 04:14 #280701
by Doug Crews
7i85s startup question was created by Doug Crews
Hi everyone. I have a 7i92t+ 7i85s flashed with 4 pwms.
At power up no operating system no linuxcnc loaded. Using a dmm I measure 5v across all step/dir -- pwm / dir pins on each TB for each instance of the differential outputs.
When Linuxcnc loads there is no change. I enable and the motor takes off at 100%.
It could be a runaway caused by an encoder wiring problem but the 5 volts present when linuxcnc isn’t loaded sounds an alarm bell for me.
Halshow displays …pwmgen.00.value = 0
Its my first PWM setup so I’ve inevitably done something to cause this. My gut tells me the pwm pins should be 0 volts on start up until commanded to move, then show some something between 0-5vdc.
Is there some hardware thing that can be checked?
-Doug
At power up no operating system no linuxcnc loaded. Using a dmm I measure 5v across all step/dir -- pwm / dir pins on each TB for each instance of the differential outputs.
When Linuxcnc loads there is no change. I enable and the motor takes off at 100%.
It could be a runaway caused by an encoder wiring problem but the 5 volts present when linuxcnc isn’t loaded sounds an alarm bell for me.
Halshow displays …pwmgen.00.value = 0
Its my first PWM setup so I’ve inevitably done something to cause this. My gut tells me the pwm pins should be 0 volts on start up until commanded to move, then show some something between 0-5vdc.
Is there some hardware thing that can be checked?
-Doug
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14 Sep 2023 04:29 #280702
by PCW
Replied by PCW on topic 7i85s startup question
With a 7I92T you can select pulldown resistors on the output that's connected
to the 7I85S. This should make the non-inverting pins (the /TXN pins) low when
LinuxCNC is not running.
Runaways may still happen because the encoder feedback or PWM direction
may be backwards
to the 7I85S. This should make the non-inverting pins (the /TXN pins) low when
LinuxCNC is not running.
Runaways may still happen because the encoder feedback or PWM direction
may be backwards
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15 Sep 2023 05:33 #280806
by Doug Crews
Replied by Doug Crews on topic 7i85s startup question
Thanks Peter, I recall seeing that information in the 7i85 documentation and telling myself to no not forget about it. but I did. I spent several hours today searching the forum, but I am still hung-up with the PWM. I inverted the output scale and still get a solid 5v across 7i85 TB2 pin 11 &12 on and after power up. It seems it's supposed to be that way? When I enable the motor is at full speed, and cannot jog at lower speed.
The 7i85 manual mentions using the differential outputs single ended for enables which I plan to explore after I get the PWM under control, but for now I’ve mapped the PWM enable to the analog enable off a 7i83 board. This seems to work without problems.
Is there something further that needs to be done with the 7i92t other than flashing it with the appropriate bit file? I am using pwmgen.XX.output-type 2 Up/down. Wiring is always a concern, please see the photo.
The 7i85 manual mentions using the differential outputs single ended for enables which I plan to explore after I get the PWM under control, but for now I’ve mapped the PWM enable to the analog enable off a 7i83 board. This seems to work without problems.
Is there something further that needs to be done with the 7i92t other than flashing it with the appropriate bit file? I am using pwmgen.XX.output-type 2 Up/down. Wiring is always a concern, please see the photo.
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15 Sep 2023 13:37 #280848
by PCW
Replied by PCW on topic 7i85s startup question
OK that cannot work since pins 11 and 12
have the same signal (inverted in one case)
First enable the 7I92T pullup option in the 7I85S connector
Then you would need to use pins 12 and 14 for RPWM and LPWM
and invert the PWM outputs:
setp hm2_7i96s.0.pwmgen.00.out0.invert_output true
setp hm2_7i96s.0.pwmgen.00.out1.invert_output true
have the same signal (inverted in one case)
First enable the 7I92T pullup option in the 7I85S connector
Then you would need to use pins 12 and 14 for RPWM and LPWM
and invert the PWM outputs:
setp hm2_7i96s.0.pwmgen.00.out0.invert_output true
setp hm2_7i96s.0.pwmgen.00.out1.invert_output true
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15 Sep 2023 19:39 #280882
by Doug Crews
Replied by Doug Crews on topic 7i85s startup question
I suspected the wiring was the problem and you said earlier I needed to invert. Thanks for showing it done, and, all the information is in the docs to do this but I’m having a “Deer in the Headlights” moment(s) with this. could be my avatar...
Here’s where things are at.
7i92t Pullup Voltage jumpers W1 are Up.
7i85s TB2 pins 12 (/TX0,STEP0 ) and 14 (/TX1,DIR0 ) wired to RPWM and LPWM
Power up the motor is now 0 velocity. But Jogging does nothing or a MDI commanded move does nothing.
PWMgen.00.value = 0 on halshow when jogging.
I think the pwmgen scale and duty cycle works out if max velocity is 1in/sec.
The manufacture of the h-bridge says it can handle up to 25kHz PWM.
I can’t help but to think there’s something not connected in the hal file.
Here’s where things are at.
7i92t Pullup Voltage jumpers W1 are Up.
7i85s TB2 pins 12 (/TX0,STEP0 ) and 14 (/TX1,DIR0 ) wired to RPWM and LPWM
Power up the motor is now 0 velocity. But Jogging does nothing or a MDI commanded move does nothing.
PWMgen.00.value = 0 on halshow when jogging.
I think the pwmgen scale and duty cycle works out if max velocity is 1in/sec.
The manufacture of the h-bridge says it can handle up to 25kHz PWM.
I can’t help but to think there’s something not connected in the hal file.
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15 Sep 2023 20:53 #280888
by PCW
Replied by PCW on topic 7i85s startup question
At the minimum P needs to be something other than 0
or you will get no output
or you will get no output
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15 Sep 2023 23:13 #280892
by Doug Crews
Replied by Doug Crews on topic 7i85s startup question
Well...Crap! That's somewhat embarrassing. I remember setting it to zero thinking I didn't want anything to influence the initial setup...Well it certainly didn't influence, at all, to the point of no movement! Hopefully others will learn from this. I have movement now.
I'm going to buy a couple more mesa boards just so I feel better about this whole evolution.
Thanks Peter.
-Doug
I'm going to buy a couple more mesa boards just so I feel better about this whole evolution.
Thanks Peter.
-Doug
The following user(s) said Thank You: tommylight
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