Several axes, one motion

One UPAN Core drives one axis. Every next axis is an UPAN Axis module on a short USB-C patch cord that carries CAN-FD. We promised synchronous motion from the start of sales, so the protocol for it is now in the firmware core, with tests on a simulated bus of three nodes.

A shared profile and one start

When a program asks several axes to move along a straight line, Core works out each axis's share of the move. Every axis gets its distance, and a speed and acceleration in proportion to that distance.

Each axis checks the move against its own limits first and answers ready or not, with the reason. Only then does Core send one start message. Everyone on the bus sees it at the same moment, so the axes start together and arrive together.

In a program this is one step:

{"move_linear": {"0": "120mm", "1": "40mm"}, "velocity": "10mm/s"}

Axis 0 is Core, 1 to 7 are modules. Before a multi-axis program runs, Core checks the extreme positions of every axis, loops included, against the limits each axis reports.

When the cable comes off

If the bus breaks in the middle of a move, every axis finishes the move it has already accepted and starts nothing new. Core then reports a bus fault with the number of the axis. If one axis faults, the others brake along the same line instead of stopping at random points.

A new module gets its number

Out of the box every UPAN Axis has the same "not assigned" number. Core finds modules by the unique ID of their MCU. You then give each one an axis number, and the module stores it. To see which box is which, tell it to blink its light.

UPAN Axis has no USB and no button. Its configuration goes through Core, and its machine limits change only over USB with the presence button pressed on Core.

Status

The protocol, the logic on Core and on the axis, and the command line commands (bus scan, bus assign, bus identify, move-linear) exist and pass their tests. The CAN-FD hardware layer and the UPAN Axis board are next.