Firmware 2.03beta2 available



  • 18 gauge is only around 0.8mm² the wiki says around 2.5mm² is recommended which is around 13-14 gauge

    Dont know if it's a pattern yet but I've read about a few issues with the duex and all those people seem to be running solid core cable.



  • Thanks, will bump up to 14 gauge. I'm using stranded wires crimped in ferrules. I'm guessing, the insufficiently thick ground would the source of my issues. I'm not sure solid core can be crimped, or tightened adequately.



  • Yes completely agree



  • @dc42 I installed a 14 gauge ground wire -- while at it also did the VIN wire. Both are 1/2 the length they were before, couldn't get shorter than this now. I left the 16 gauge(it was 16 not 18 before) going to the PSU, it's coupled in a ferrule together with a very short 14 gauge jumper to duex5. The printer itself with everything on never pulls more than 200w, since my I'm using an AC bed, 16 gauge wire has not been an issue for 24v DC power.

    Now the main question is, how do I test the i2c bus for reliability. Under normal conditions it takes a long time for me to start seeing timeouts, is there a test routine, something that would send a bunch of data on i2c which you would expect to produce some errors if the wiring was at issue (I don't mind running some custom firmware to bang on the i2c bus).

    Thanks again.



  • Will do later today.


  • administrators

    @kazolar said in Firmware 2.03beta2 available:

    @dc42 I installed a 14 gauge ground wire -- while at it also did the VIN wire. Both are 1/2 the length they were before, couldn't get shorter than this now. I left the 16 gauge(it was 16 not 18 before) going to the PSU, it's coupled in a ferrule together with a very short 14 gauge jumper to duex5. The printer itself with everything on never pulls more than 200w, since my I'm using an AC bed, 16 gauge wire has not been an issue for 24v DC power.

    Now the main question is, how do I test the i2c bus for reliability. Under normal conditions it takes a long time for me to start seeing timeouts, is there a test routine, something that would send a bunch of data on i2c which you would expect to produce some errors if the wiring was at issue (I don't mind running some custom firmware to bang on the i2c bus).

    Thanks again.

    You could try sending repeated commands to change the speed of the DueX fans. Each one will require an I2C transaction.

    Here's another possibility: pick one of the DueX servo outputs that corresponds to an unused heater channel, connect the servo control pin of that output to the cathode of a small signal diode, and connect the anode of that diode to one of the DueX endstop inputs. Then use M307 to disable that heater, and M42 to set up 50% PWM on that servo output at a low frequency. Every time the endstop input toggles, the DueX will signal a change to the Duet, and the Duet will do an I2C transaction to find out what changed.



  • Is there a certain resistance that shouldn't be exceeded on the ground connection between the boards? I've got really thick wires running from both boards to the power supply and I measured the resistance to be somewhere around 0.4 Ohms. Since I get the errors extremely rarely, I added an additional, short but significantly thinner wire between the boards, which appeared to halve the resistance. Would this be good enough?


  • administrators

    @edgars-batna, you should be looking for 0.1 ohms or less. Bear in mind that your multimeter may read greater than zero ohms when you short the leads together, in which case subtract that value from the reading you get between the two terminal blocks. My multimeter reads 0.2 ohms between the ground side screws of the two VIN terminal blocks, and also 0.2 ohms if I short the leads together.

    Inductance matters too, which is why the wire must be kept short. The reason is that the stepper motors draw large pulsing currents when they are energised, and this will cause there to be ground noise between the Duet and DueX unless that wire has low resistance and inductance.



  • @dc42 Thanks, it's exactly as you described, so I suppose the value should be good enough now.



  • @dc42 I ran some gcode shifting fan speed for tool 3 (fan on the duex5) repeatedly a few hundred times and no i2c errors or timeouts. Wonder if that means it's solved. I'll try the servo trick. Would adding the resistors hurt any?


  • administrators

    Adding the resistors won't hurt. We're going to reduce the values of the ones on the DuetX in the next manufacturing batch.



  • Just posting here to confirm that 2.03 beta is working fine on my CoreXY with sensorless homing.

    here is my last print (printed in ABS):

    0_1552824161524_behelit.jpg

    it's a sleeping Crimson Behelit. (Berserk fans will know what this is 🙂 )


 

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