Quadrigotion: Multiple Motor Drivers, one connector
Often it is useful to have all the motor drivers needed for a machine on a separate circuit board to be able to mount it to a heatsink or close to the action. This is what this project is about. The name Quadrigotion is a word amalgamated from 'Quadriga' (Four horses powering a chariot) and 'Motion'.
Motivation for this project to have motor drivers easily replacable and testable on my various 3D printers and CNC machines. Since I am also developing motion control software, I might have an unusual high demand for this :)
The idea is to have a common connector type, described below, and various implementations of that concept. The first implementation is using a TMC2660, which is the 'big brother' of the more well-known TMC2100.
Other implementations are conceivable e.g. with Pololu modules, DRV8825, or super high current and voltage drivers for heavy CNC machines. Implementations can be super bare-bone and not use the SPI connection or could be configured via SPI using a shift-register and digital potentiometers if the chips can't be configured with SPI directly. While the first Quadrigotion implementation happens to also have four motor drivers, this could of course extend in the future.
The Connector
The digital input is provided with an IDC connector with 16 pins (2x8) or 20 pins (2x10). It features a SPI bus to send configuration data and also read motor/driver status (the actual protocol is of implementation-dependent, but they all can share the same hardware interface).
| Desc | Pin | Pin | Desc |
|---|---|---|---|
| GND | 1 | 2 | VCC (3.3V-5V) |
| All Motors ~Enable | 3 | 4 | (not connected; reserved for fault-out) |
| ~CS (SPI) | 5 | 6 | CLK (SPI) |
| MISO (SPI) | 7 | 8 | MOSI (SPI) |
| Step #1 | 9 | 10 | Dir #1 |
| Step #2 | 11 | 12 | Dir #2 |
| Step #3 | 13 | 14 | Dir #3 |
| Step #4 | 15 | 16 | Dir #4 -------- END IDC 16 variant |
| Step #5 | 17 | 18 | Dir #5 |
| Step #6 | 19 | 20 | Dir #6 -------- END IDC 20 variant |
It is easy to see that extending the driver count would just require a wider IDC connector; the serial configuration interface can deal with any number. A 16 pin IDC connector allows for 4 steppers, the next configuration with 20 pins would allow for six drivers.
A single Enable-pin is provided that affects all drivers. This makes it easy to wire up that signal directly e.g. for emergency buttons. If more individual control of each driver is needed, this can be done via the SPI connection.
The fast signals for each stepper, step and dir, are provided in a parallel input with two lines per stepper.
A Quadrigotion connector has a single ChipSelect signal; multiple drivers on each implementation have to share that bus, e.g. by internally being organized as a shift register that latches when ~CS goes high again.
One pin (pin 4) is not connected yet, but it is reserved for fault detection output (e.g stalling, overheating or over-current).
In an upcoming project, I'll build a breakout board to work with BeagleG.
TMC2660 Implementation
The first implementation is based on the TMC2660, a feature-rich motor driver that can drive up to 4A (2.8A RMS). The 40mmx125mm PCB is a four layer board which duals as heat conductor for cooling. Multiple M2.5 mounting holes allow to firmly mount it to a heatsink and get even pressure to individual silicone heatsink pads. Power is provided via a 4-pin JST VH connector (3.96mm pitch), circuit protected with an automotive ATC Mini 297 blade fuse.
You find the gerbers in the fab/ directory. Board is also shared on OshPark. Cave: since this is the very first version, no testing has been done yet with a physical board.
