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[upahill]

Hi All,

Received my pre-programmed chips today (Thanks Tom) and assembled the board - I was half expecting magic smoke but everything seems ok on that front. But I cant get any connection with the config utility.

With power and USB connected I get a solid power light, solid status light and flashing usb light. Drivers are installed and COM port is set.

If I try to use the config utility to read the config it gets to :011 and then errors out.

Trying to do a firmware update gives programmer is not responding error.

Have tried reseating the chips, checked all my solder joints etc but any ideas would be appreciated.

[TCWORLD]

Did you connect USB first of 12V first? 12V should always be connected first, otherwise you can end up with comms issues.

You'll need to upload the firmware successfully first before editing the config. The ICs are pre-programmed with the bootloader only, which will allow the firmware to be uploaded over USB using the config utility.

Status light shouldn't be solid on at this stage, so I'd double check there are no shorts around it or its pins.

[upahill]

Did you connect USB first of 12V first? 12V should always be connected first, otherwise you can end up with comms issues.

You'll need to upload the firmware successfully first before editing the config. The ICs are pre-programmed with the bootloader only, which will allow the firmware to be uploaded over USB using the config utility.

Status light shouldn't be solid on at this stage, so I'd double check there are no shorts around it or its pins.

Triple checked for shorts and thought I had identified one but it looks like they are connected in the pcb anyway. It did work for a few minutes, long enough to upload the firmware - doing the same again now though so at a loss as to what is causing it. The body of the USB socket is extremely close to the diode D2 - microns away.

[upahill]

Not a short on the USB body, finally figured out how to make my new multimeter do a continuity test 

Any other ideas on what could cause it? Status LED is staying solid when plugged in to just the 12v

[TCWORLD]

Could you post a photo of both sides of the board, in a decent resolution.

[upahill]

They are just uploading now, please excuse my soldering - its not pretty but thought it was functional 

My electronics experience is limited to GCSE 15 years ago but looking at the schematic it appears the status led should only be able to be on if pin 8 (SCK) is high, which it is. Resetting the IC using the ISP pins switches off the LED. Powering up without the main IC in doesn't enable the status led.

Was super excited when it worked briefly, hopefully I can recreate that with a little help!

[upahill]

+2 more pics

[upahill]

Found the problem! Woohoo.

It appears to be a slighty iffy 40 pin IC socket, the solder joints were ok but it wasnt making great contact on one of the pins internally.

Bit of jiggling and it seems to work ok right now. Thanks for the help Thomas and speedy delivery - might have to get another as a backup soon anyway.

On to wiring up some motors.....

[upahill]

Almost there... just got one final problem to overcome I think.

I can get the motors to turn providing there is only one driver plugged in to the board. As soon as the second driver is installed both axis fail to initialise.

I have tested all DRV8825s independently in both the slot for the RA and DEC drivers, tested both cables individually and both motors. If I only had one axis it would be fine in any config. But as soon as both motors and both drivers are connected it flat out refuses to do anything.

Any ideas appreciated.

[TCWORLD]

Have you set the current limit on the drivers? (See FAQs page).

Also, what is the current rating on your 12V supply?

[upahill]

I rewired the RJ11 connectors after painstakingly checking the wiring and if I follow the diagrams / logic the motors dont run, but if they are wired up wrong they do work. I have checked the pins on the connectors and they mate up to the correct pins on the drivers so very confused.

Power supply is a 5A 12V. I have tried to set the current rating but im getting some strange readings from the vref - measuring from the via to the ground pin gives me 12v, adjusting the pots does nothing to this reading. Im beginning to think the drivers might be screwed up - I have borrowed them from a working 3D printer - but they are probably knockoffs and not genuine polulu.

From your guide to setting the current limits I would have expected that vref via measurement to be 1/10th what it is at most.

 

[TCWORLD]

If they are clone boards, you'll need to not measure voltage not at the VREF pin, but the middle pin potentiometer directly.

The people that cloned them screwed up and wired the VREF measurement point to VMOT (+12V) rather than VREF.

Sometimes when wired up correctly, if the current is set too high or too low, the motor wont spin.

The pin-out for the RJ11's is:

Code: [Select]

(Pin) -> (Motor Coil)
  2   ->    A
  3   ->    B
  4   ->    B
  5   ->    A
If you wire them up in a way that switches part of A with part of B, (e.g. ABAB or BABA), they won't work properly even if they do spin a little.

[upahill]

Yeah i probed from the pot to the gnd pin and managed to adjust them to about .4 - the motors are running a little warm still but everything seems to be working. I assume that because they are working they must now be correctly wired up Have bought some coiled cables and some RJ11 breakout PCBs which should help tidy things up too.

Played around with Cartes du Ciel a bit last night and after reversing both axis I think its slewing in the right directions now. The gear ratios seem to be off as the distances it moves compared to the reticule on screen are quite a bit different. Im going from the NEMA with a 16T to the worm screw with a 40T so have set the ratio to 2.5, 144 for the worm which I thought was right but im guessing I need to check my math somewhere there.

Thanks for the pin out ref, i will no doubt need it again soon!