gQuintic Specs

gQuintic Specs

• Runs g2core codebase

• Processor

  • Atmel SAMS70N19A ARM Cortex M7 processor
  • 300MHz internal clock
  • 32 and 64 bit single instruction floating point hardware
  • Multi-level cache, instruction pipeline, simultaneous instruction execution
  • All communications IO is DMA driven
  • USB is on-chip (w/custom USB drivers - field tested for about 2 years now)

• Host and Communications

  • USB-B connector for driving from "standard" external hosts
  • Host expansion connector for Linux host carrier board
    • Board design accommodates wide variety of linux hosts such as nanoPi family, Beaglebone, rPi, etc.
    • Host-to-board communications via 4 wire UART - RX/TX/RTS/CTS
    • 1.2 Amps 5v @ 1200 ma available for host processor

• Motors

  • 5x Trinamic TMC2130 stepper motor drivers
    • Will handle up to 1.7 amps;
    • Good for almost all NEMA17 motors, will do some NEMA23s
  • 5x STEP / DIRECTION / ENABLE breakouts for external drivers (in lieu of Trinamics)
    • selectable 3.3v/5v output levels
  • 4x "hobby servo" PWM outputs (uses the buffered digital outputs)
    • can be configured to interpret Gcode directly, or run as PWM devices

• Inputs

  • 10 input protected 3.3v digital inputs
  • 4x analog to digital inputs
    • configured as straight-through 0v-3.2v ADC channels
    • external analog front-end boards can be used to run 100K thermistors, PT100, PT1000 RTDs
    • OEM boards can be configured on-board for these front-ends

• Outputs

  • 4x buffered digital outputs - selectable 3.3v/5v level
  • 4x low-power FET digital outputs - up to 300 ma each (fans, etc.)
  • 2x high-power 6amp FET digital outputs - for extruders
  • 1x high-power 20A FET digital outputs - for heated bed
  • 0v-10v DAC output for spindle controller
  • Neopixel LED array output with DMA firmware driver

• Other

  • Can be configured for separate 24v motor and logic input to support eStop that cuts motor power while leaving controller board and host live to handle whatever hit the fan.
  • SPI and I2C expansion port
  • Watchdog safety circuit to disable powered outputs
  • Can remove motor/output power w/o killing logic power
  • JTAG/SWD connection and real-time debugging using Atmel-ICE
  • ROHS

Features

Watchdog Safety Circuit

Most product safety certifications (e.g. CE for Europe) for things like machine tools require that a redundant hardware failsafe be provided to shut down the machine in various failure cases. This should be in hardware, unless you have a software solution that is separate form the main SW, and the failsafe SW itself then needs to be certified (which we want to avoid).

The gQuintic has a discrete multivibrator circuit made of two cockroach FETs (BSS84, BSS138) that asserts as long as a pulse train is present on the input. If the pulse train is not present or fails the safety circuit de-asserts. All the output FETs and the step signal are gated by this SafeOut signal. The pulse train generator is in the main loop of the MCU.

Here are conditions where the pulse train would fail:

• The MCU is booting - and has not started the main loop yet
• The MCU is being flashed (and therefore not executing)
• Motor power is applied but for some reason logic power has failed or not applied (the MCU is therefore not functioning)
• The firmware is off in the weeds and the main loop has been terminated accordingly (Note: there are a series of assertions that are also run as part of the main loop that will shut down the machine if a fatal error is detected)

Emergency Stop and External Shutdown Options

First, some background and philosophy: Since the controller may be the cause of a problem requiring an emergency stop, the controller should never be in the critical path of an emergency stop.

With that in mind, the board is design so that motor and FET power can be killed by an external switch independently of the processor continuing to operate. The incoming Vmot (typically 24v) has two connectors - One high-current to power the motors and FETs, another low-current to feed the regulator stages. These can be bridged for single-connection configurations.

If Vmot drops a number of things happen:

• The motors, FETs and DAC de-power - this includes the high-current FETS (heaters), and the low-current FETs and the DAC output will drop to zero (The DAC is 0-10v, typically used for spindle speed)
• The Trinamic rail voltages drop in order to prevent them from blowing up (which they will if you don't remove power)
• The CPU receives a LO on a pin, which can be used to signal the firmware that an external Estop has occurred (really that Vmot has been lost). The firmware (as it stands now) enters a Shutdown sequence, where it stops motion, shuts off the Safety signal, and informs the host that this has occurred.