Opentrons: How to connect to the OT-2 via serial connections to send my own G-code

[zachaayuna]

Hello, I am using the opentron to write my own G-code driver and was wondering what the best way would be to connect to the OT-2

[nickcrider]

Hi there @zachaayuna thanks for writing!

The OT-2 uses a smoothie motor controller, and that's connected via UART to the robot's RaspberryPI's GPIO pins.

Here's our implementation of the G-code driver https://github.com/Opentrons/opentrons/blob/edge/api/src/opentrons/drivers/smoothie_drivers/driver_3_0.py

But, would you mind sharing a bit more about what you're trying to do and why you want to write your own G-code driver for the robot? I unfortunately don't think I have enough info from you to be of much help right now.

[zachaayuna]

So we are not using it to pipette we want to change the head and control the machine using our own G-code driver or maybe make adjustments to yours to suite our needs. I was just trying to directly connect to the smoothieboard so I can customize the movements of the machine.

[zachaayuna]

Or more simply, How would I be able to run my own driver on the OT-2

[zachaayuna]

Would I need to take the outer shell off and plug directly into the board? We want to be able to control the movement in very specific ways.

[theosanderson]

(Am fellow user not dev).
In theory you can send GCODE with driver._send_comand https://github.com/Opentrons/opentrons/blob/edge/api/src/opentrons/drivers/smoothie_drivers/driver_3_0.py#L980 It's worth thinking about what you want to command it to do that you can't do by commanding the gantry to move to a particular position, e.g.

protocol._hw_manager.hardware.move_to(
            types.Mount.RIGHT, position, speed=speed)

[nickcrider]

Thanks @theosanderson ! You took the words right from my keyboard!

@zachaayuna, my advice is that you spend some time considering the recommendation from our user above. The API does an awful lot of work to help transform the smoothie coordinates into "deck coordinates" that correspond to physical positions on the robot deck. I don't want to doubt your abilities, but I also want to make sure you don't waste a bunch of time reinventing the wheel.

But despite that, if you still decide that you'd like to do it your own way (it's opensource after all, more power to you!), you can start taking apart the robot, access the relevant pins on the smoothie, and drive it however you want.

Hope that helps!

[zachaayuna]

Ok thank you @nickcrider

[zachaayuna]

Can I use the opentron api to move to exact positions by sending coordinates

[theosanderson]

Yes,

from opentrons import types
protocol._hw_manager.hardware.move_to(
            types.Mount.RIGHT, types.Point(100,100,100))

(exact snippet untested)

[zachaayuna]

Works perfectly Thank you! @theosanderson

[zachaayuna]

Hi @theosanderson ,

Is there a way to move the one Z axis without the other coming back up to starting position

Thank you

[theosanderson]

You could write your own version of move_to without cache_and_maybe_retract_mount https://github.com/theosanderson/opentrons/blob/edge/api/src/opentrons/hardware_control/__init__.py#L711 or move down to a lower level command looking at move_to for inspiration.

[zachaayuna]

Ok thanks

[zachaayuna]

@theosanderson whe i ssh to the robot do i change the python files in data/packages/usr/local/lib/python3.6/site-packages/opentrons or where can I enter the functions on robots rasPi

[zachaayuna]

I have just been playing around with the machine to understand functionality and and trying some things out and just had some questions and you
@theosanderson seem very knowledgeable on the topic so thank you

[theosanderson]

You don't want to change the opentrons library itself. Write your own functions that call on some of its functions. Here is some code where I've done that. https://github.com/theosanderson/tube_checkout/blob/master/tube_checkout/tube_checkout/tube_movement.py You can do that in Jupyter for example, especially for prototyping

[theosanderson]

So write your own move_to but keep it in your own code

[zachaayuna]

I understand and then you just run that as protocol then

[theosanderson]

Yes or you can run it via SSH / Jupyter

[zachaayuna]

Okay thanks

Sent from my iPhone

On Jun 23, 2020, at 3:04 PM, Theo Sanderson [e-mail] wrote:


Yes or you can run it via SSH / Jupyter

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