I came across this ARM Cortex M3 board $39.90 with SD/MMC socket built-in:
[www.futurlec.com]
I think with 32-bit processing power we can control Reprap including all steppers and the extruder temperature with this one microcontroller.

This does look good! Especially the price

However... a few remarks. The current Arduino is even capable to drive my Delta RepPrep complete with all four steppers and extruder. OK, granted, the extruder itself hasn't been functioning yet but thats not due to lack of processor power. As for the SD card; pin assignments on the Arduino are tight but enough and for the extra code size needed for a nice SD/MMC file interface a Sanguino might be handier due to its enlarged code space but otherwise....

The main benefit I see for that is the I/O ports being on the standard 10pin IDC connectors, which should allow easy interfacing to standard Stepper controllers.

Could be a good development starting point.

And its not too expensive either.

are you saying with this one board we can control our stepper motors directly we wouldn't have to buy controllers for every motor? I'm planning my repstrap right now, should I use this board, I just ordered 4 nema 17 motors about 30 minutes ago, will this work with those?

And it goes directly to usb so we wouldn't have to worry about goofy cables that cost us 20$ extra

We could be looking at 100$ savings with this board.

What sort of power interface does this board use?

From what I can see, you'll still need stepper drivers. I count that as a plus, as a burnt-out stepper driver is easily replaced, whereas a burnt-out mainboard is not (or at least, more costly).

Greetings all,

The same company offering this Cortex M3 board also offers a high (-er power than our current gen 3 or 4) stepper controller boards, the [www.futurlec.com]

The documentation is thin (no schematic), so it's not clear yet to me whether one would need a '297 to provide an equivalent (to our current) step/direction interface. However, the price low enough that I'll probably include one in my next order to these folks. They spec this board as handling up to 5 Amps @50 volts, so this may be good for those who want more torque, e.g. to drive a heavier machine.

I've used a similar Cortex-M3 board from these folks (without the SD/MMC slot), and it's worked fine for what little I've done with it. Details in my (very occasional) blog.

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Larry Pfeffer,

My blog about building repstrap Cerberus:
[repstrap-cerberus.blogspot.com]

The L298 was originally designed as a dual, brushed, DC motor driver. With a stepper motor, you have two complete sets of windings and drive phases, so it takes twice as many H bridges per motor. The L298 usually takes a forward and reverse PWM signal for each motor. To drive this as a stepper motor, you might need 4 pins to provide the forward phases and the reverse phases. Compared to the Polulu or SparkFun stepper drivers, that take step and direction inputs, and provide optional micro-stepping, this looks like a step backwards. I really like the l298 for low power motor drivers, but unless there is a whole lot more smarts on that board then I can see, it will not work as well. The small dip package in the front is probably the Vcc to 5Volt regulator that the L298 needs, so there does not appear to be ANY additional processing power in this layout. Putting a ATtiny surface mount in to convert a setup and direction input into microstep PWM for the forward and reverse phases would not have added much to the cost, and made it more competitive with other, existing stepper drivers.

Mike

btw, on the arm cortex m3, very interesting board

[olimex.com]

it is in bit more expensive (80$) but comes with STM32F103RBT6 ARM 32 bit CORTEX M3™ mcu (128K Bytes Program Flash, 20K Bytes RAM, USB, CAN, x2 I2C, x2 ADC 12 bit, x3 UART, x2 SPI, x3 TIMERS, up to 72Mhz operation), the lcd (BW 84x48px PCF8544 compatible - aka nokia3310 spi screen) and IDC connector, USB mini connector, 3-axis accelerometer (this can be used to determine if our printer is "shaking" while printing , SD-MMC card, 2.4 Ghz transciever (anyone mentioned wirelles??), user buttions, Joystick with 4 directions and push action (manual control anyone) ...

I think this would be ideal 32bit core for new reprap's (btw, bfb's pcb uses 32bit pic with oled display and it really works very nice, fully stand alone ... so going 32bit might solve some issues )

The Mbed dev board I am currently using, has an LPC1768, 100Mhz Cortex M3 ETHERNET, USB, CAN x2, UARTx4, SPI, I2C etc etc, 512k flash and 64k Ram, and their around $60.

The documentation is thin (no schematic)

I sense this is a slightly non-gpl board which will be very difficult to print at home.

Carry on.

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-Sebastien, RepRap.org library gnome.

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