RepRap SNAP Command Documentation

Communication Protocol

These modules communicate using the SNAP Communications library. This is an implementation of the SNAP Protocol in a ring network.

Protocol Version 1

• Stepper Motor Controller - control an individual linear axis
• Thermoplastic Extruder Controller - control an individual heater-based extruder

Global Commands

These commands should be implemented by every single device with an address.

[0] Get Version

Returns the version of the module. This message is the only message universally supported by all devices and is therefore useful as a test.

Parameters:

• None

Returns:

• 1 byte: Response type (0)
• 1 byte: major version number
• 1 byte: minor version number

[255] Get Module Type

Returns the type of the module. This message is used to query every device in the network to determine what types of devices are connected. For example: the RepRap host software queries all devices for their type, compiles a list of connected devices, then queries each device for its version. From there, it can easily autoconfigure its internal software and automatically communicate properly with each device in the network. All this can be done transparently to the end user.

Parameters:

• None

Returns:

• 1 byte: Response type (255)
• 1 byte: module type (see table below)

Module Types:

Id	Type
3	Cartesian Robot
5	Cutting Toolhead
4	Laser Cutter/Etcher
0	Linear Axis / Stepper Controller
2	Support Extruder
1	Thermoplastic Extruder

Allocated addresses

• 0 PC
• 1 Master controller (not currently used for ring network)
• 2 X axis
• 3 Y axis
• 4 Z axis
• 5-7 Reserved for 6 DoF^? platforms (Stewart platform etc.)
• 8..27 Extruders 1 to 20
• 50 IOBox test tool

Next Generation Protocol Ideas

Protocol Modules

• Cartesian Robot - a single device representing 3 linear axes
• Thermoplastic Extruder - a simplified extruder device.