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Topic: MC433 - TWI/I2C interface (Read 1 time) previous topic - next topic

3dprinter

Jul 17, 2012, 09:43 am Last Edit: Jul 23, 2012, 09:25 pm by Msquare Reason: 1
I have this 2nd hand MC433 which I am trying to drive a CNC table with. It is designed for that. The MC433 is an old design (2006) and assumes a LPT interface for connection ;) No problem for my trusty Arduino, and I am able to to step my steppers with it in a controlled fashion, but it is jittery.

One of the avenues is that the MC433 has a TWI/I2C interface and NO/Zero/nada documentation on that. The manual says it can "talk with each of the control processors to set PWM parameters, step the motors, change step sequence (wave, full or half step), change motor turn off conditions, change chop frequency and request status." which is much more than can be done withe the LPT interface (basically just step pulses). The manual concludes "The protocol used between the MC433 and an external TWI controller is described in a separate document." I have not been able to find such a document (not even on the SOC robotics own pages)

Anyone out there have any info, experience or such like?

MarkT

Well there is a software download that you could try to reverse-engineer - it talks over USB to a USB/I2C converter apparently.

"MC433 Motor Control Software V0.99b" on the downloads software section - Windows only :(
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

3dprinter

try to reverse-engineer
Bit too much for me, I am afraid. It also uses a .dll to get at the LPT port - so the program refuses to start on a pc without a LPT.

3dprinter

Update: SOC Robotics have been kind enough to send me some info - they never got round to write the doc. So I got some source to look at to work it out  :smiley-eek: ... this is going to take some time. :|

Chagrin

It looks like a pretty standard design. Figure 2-1 of the tech doc shows the pinout for the parallel port. The paragraph below it notes that the four limit switch pins needs to be pulled high with a 10K resistor; this is probably your stumbling point in getting it working.

3dprinter

Hi Chagrin, no problem with doing the LPT ports, with direct connection from the Arduino. According to the schematics they go directly to the motor-controller (an ATmega48) so no problems with levels/currents there. The schematic shows a pullup on the limit switches and the doc says it only needs a pulldown to ground, so they should be OK to float (of course, simple enough to set up a pullup...)

My question is about using the TWI/I2C interface. On this interface you get to talk to motor controller to set some scaling factors, which it stores in its EEPROM and retrieves/uses on powerup.

If the only purpose is to drive the steppers I would use something else - got plenty of modern stepper-drivers. But the fun-of-the-game is this MC433 board (until it gets too difficult)

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