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Replicape is a 3D printer cape for BeagleBone.
Hardware features:

• 5 stepper motors (2.5A DRV8825) (X, Y, Z, Ext1, Ext2)
• 3 high power MOSFETs (PWM controlled) for 2 extruders and 1 HPB. (12..24V)
• 3 medium power MOSFETs (PWM controlled) for up to 3 fans/LED strips. (12V)
• 3 analog input ports for thermistors. noise-filtered inputs and option for shielding
• 6 inputs for end stops (X, Y, Z).
• 1 bus for Dallas 1W temperature sensor for monitoring the cold end. Up to 10 sensors can be added to the bus.
• Programmable current limits on steppers motor drivers (SMD). No need to manually adjust a pot meter.
• Microstepping individually programmable for each SMD from 1 to 32.
• All steppers are controlled by the Programmable Realtime Unit (PRU) for hard real time operation.
• Option for stackable LCD cape (LCD3). HDMI compatible LCD on the way.
• Single 12 to 24V PSU, fans are still 12V.
• Comptabile with BeagleBone and BeagleBone Black.
• Open source hardware and software.
• Software written in Python for maintainability and hackability.

Software features:

• Accelleration with corner speed prediction.
• Printer settings loaded from file (Version 0.4.2)
• Controllable via ethernet, USB, printer display.

TODO for software:

• Make a fancy GUI with 3D model
• Implement realtime slicing on BeagleBone so an STL file can be sent directly (very cool, Koen is working on this).
• Better axis max-speed. It now limits the feed rate, but should instead take into account the speed in a given direction.
• PID autotune.
• Constant jerk.

Known issues:

• USB hugs all CPU, disabled for now. Use ethernet (over USB) instead.

Fixed issues:

• Optimize the merging of timings from the different steppers.(Fixed in verison 0.5.0.)
• Long stretches of stepper movement that occupies more than the available 40K of memory are not cheked and kills the whole shebang. Must be fixed. To reproduce, try moving the Z-axis 20cm.
• Temperature sometimes not available. (OK now, checks multiple times if not available. Fixed in 0.5.3)
• Implemented axis max-speed, configurable from the settings-file.
• When slicing with slic3r, the printhead often stops to "think" (before shifting Z etc). This happens even though the PRU is pull of commands.(It was since G92 was not buffered)
• The amount of available DDR memory for the PRU shrinks causing the program to crash for unbuffered commands. By logging the amount of available PRU memory used during a print, the amount availabe at the end of the print is not 0x40000 and pru.wait_untill_done() never returns. This could be eith due to skipped events or wrong memory reporting in the commit_data() function of the PRU. The print should still finish as expected, though.
• Better temperature control. Temperature control was coarse due to a badly written ADC driver fetching old values. Fixed and patch sent in.

Blog: http://hipstercircuits.com
Wiki: wiki.replicape.com