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Gen7 Board-ARM v2.0

The second prototype with all the planned features on board.

The second prototype with all the planned features on board.

Back of the same board.

Back of the same board.

Generation 7 Electronics Board-ARM v2.0 is the first Gen7 based on an ARM, an LPC1114FN28. Like all earlier Gen7s it's still easily DIY-able, because this FN28 comes with through-hole pins spaced at 0.1“ (2.54 mm).

Compared to earlier Gen7s it's considerably faster. It has been demonstrated to deliver as many as 130'000 steps/second to the stepper driver, so 1/32 microstepping is no longer a bottleneck. Even at 1/128 microstepping one can achieve reasonable performance.

Status: refined circuitry design & board done.

Features

  • Support for up to 4 stepper drivers in the “Pololu format”.
  • Support for extruder and heated bed.
  • Support for two SPI devices (e.g. SD card and display).
  • No power supply wiring neccessary, just plug and be ready.
  • Software power on/off.
  • Oversized high current tracks and MOSFETs for reliable, cool operations.
  • Board size 110 x 90 mm.

Commissioning

Soldering completed? Fine. All obvious flaws, if any, fixed? Excellent.

I'ts good manufacturing practice to do some measurements on the board before inserting the central chip, the MCU. Not only because the MCU is the most expensive part on the board, also because this parts connects many other parts together, so a fault in one section harms other sections, too.

For all these measurements a cheapo voltage meter is entirely sufficient.

Measure Standby Voltage

  • Plug the ATX24 connector of your ATX power supply (PSU) into the board. PSUs with only 20 pins on this connector work, too.
  • Connect the PSU to a mains (110/230 volts) outlet.
  • Turn the mains switch of the PSU, if present, on.

At this point the yellow LED on the board should light up. If it doesn't, find the cause and fix it.

Voltage measurements on standby power.

Voltage measurements on standby power.

To make this step complete, measure the voltages shown in the picture. Deviations of half a volt are OK, but substantially different voltages, especially ones above 6 volts, are not. GND of the meter can be connected to one of the black wires of the ATX24 connector. All other pins of the LPC1114 socket should read (close to) zero volts.

With these steps done you can be reasonably sure to not burn your LPC1114 when inserting.

Firmware upload

Gen7-ARM runs Compilation Environments. Not yet featured with Configtool, so it has to be compiled using the Makefile on the command line.

Details on this TBD.

Other firmwares are possible, of course. Be aware that most won't fit into program memory (32 kB) and are expected to be slower.

For details on uploading firmware in general see LPC1114 Bootloader.

TODO

Board-ARM v2.0 is the latest development, so let's collect here experience and possible enhancements for the next version.

Make auto-reset work

For an idea using the serial control lines see http://www.mikrocontroller.net/topic/281717#2977141. Not sure wether this can really work for programming, though and for printing it's sometimes even counterproductive (like when continueing an aborted print).

History

December 2012

Board of the first ARM based Gen7 prototype.

Board of the first ARM based Gen7 prototype.

The first ARM based Generation 7 Electronics was created. It was mostly a Gen7 v1.4.1 with the ATmega replaced by an NXP LPC1114FN28. It worked on the spot.

February 2013

Bobc's proof of concept video

RepRap user Bobc was the first to run a printer with a Gen7-ARM.

See also his RepRap forum post. To get a working firmware he ported Teacup Firmware to ChibiOS. Later investigations showed that this choice didn't exactly result in the best possible performance, but this didn't matter at that time.

gen7_board-arm_2.0.1447682771.txt.gz · Last modified: 2018/05/27 16:10 (external edit)