3 Servos and 1 Stepper on a 7i77 +5i25

Hi Guys,

I'm working on a trivkins 4 axis mill retrofit that started as a 3 axis servo machine. No problem there, but I'd also like to add a stepper driven 4th axis. Is there a way to control that 4th axis through the 7i77 without another daughter card being added to the mix? Thanks in advance.

Mr. Technical

Not really but you can add a low cost parallel port breakout board to the 5I25s P2
(or just connect the P2 pins directly if you are careful...)

That's good news! Which parallel port breakout board would you recommend? I only need to send it step and direction signals, with minimal IO to release the brake. Encoder feedback would be a big plus.

Also, will PNCCONF be able to help configure it, or am I going to have to hand edit the HAL file?

Mr. Technical

You will likely have to hand edit the HAL file

You will also need a custom bitfile that matches the breakout board that you choose.
If you post a link to the specs of the breakout you want to use, I will make a bitfile for it (7I77 on P3, BOB on P2) and add it to the standard pinout library.

Thanks very much for the offer of a custom bitfile. I really like Mesa's (your?) products, so if they/you have something suitable, I would start there. Like I mentioned, I just need to send it step and direction signals, the ability to release the brake, and hopefully get encoder feedback if that's not asking too much.

Mr. Technical

yes there is a 7i77_7i76 firmware.
The step gens are on connector 2 so you could connect to the directly and not use a 7i76.

PNCconf should work fine for this as long as you don't assign anything to the 7i76"s smart serial tabs

Chris M

Hi Chris,

Thanks for the good information! I was able to set up the I/O connector 2 tab up with the A-axis stepgen on number 0 and then set up the A axis motor/encoder configuration page up for use with a Gecko 203V, even though I'm really using a DM542A from Longs Motor as the driver.

Since I'm using the 5i25 as the source for the second parallel port, how should I set the I/O Control Ports/Boards section of the Basic Machine Infirmation page?

I'm getting a terminated with an error when trying to run the config that I set up. I should mention that I have power applied to the 7i77 board and was able to open Linuxcnc before I started messing with the A -axis. I don't have the driver with me at the moment, so that's not hooked up. Thanks in advance!

Mr. Technical

I've attached my error file. I think the applicable information is the following:

Debug file information:
Can not find -sec MOT -var MOT -num 1
Can not find -sec IO -var IO -num 1
Can not find -sec LINUXCNC -var NML_FILE -num 1
Can not find -sec EMC -var NML_FILE -num 1
FMT.hal:219: parameter or pin 'hm2_5i25.0.stepgen.00.dirsetup' not found
3418

Thanks,
Mr. Technical