7i94 vs 7i92M / 7i74 combination?

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15 Oct 2019 12:34 #147927 by ross_dev
Hi

I would like to connect our PC via an Ethernet MESA Anything I/O board, and I have some experience with the 7i92M and a 7i74 breakout combination. In past applications and the present one, this chains onto a set of STMBL drives, hence the need for the RJ45 connectors to the drives.

We need to send PWM signals to BLDC motors, with encoders (closed loop control). Is there any reason why the 7i74 would be inappropriate for this?

As an alternative, with the 7i94 is a breakout board required, or does it fulfil the function of both an Ethernet board and breakout board combination? If it can do both it is very appealing, combining PC / Ethernet connection and an array of RJ45 connectors in one package.

Thanks for your ongoing help!
RD

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15 Oct 2019 12:37 #147928 by tommylight
It sure looks like
7i92+7i74 = 7i94 plus DB25 !
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15 Oct 2019 13:28 #147929 by ross_dev
The only possible fly in the ointment is that the 7i94 has capacity for only "one PWM generator". I do not fully understand whether LCNC or the motion control card generates the PWM signals, which we need to drive our BLDC's. If I am going with a potentially high latency laptop, and taking advantage of the motion control card to do the heavy lifting, would this mean I need FIVE PWM generators to drive all my motors?

Or is this handled by the eight SmartSerial Connections on the 7i94? I still have a great deal of learning around these topics so I apologise for the multiple questions.

I believe there is an additional daughterboard to increase I/O options, but I am not sure if this solves the "PWM generation" problem (if there even is one). Any advice would be much appreciated!

Cheers

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15 Oct 2019 15:32 #147934 by PCW
A 7I94 _is_ basically a 7I92+7I74 (that mounts in a 107MM DIN tray)

Its a bit fancier in that it has xmit enable on all channels and can be
powered by 8 to 40VDC

Not sure what you mean about the PWM generators

1. You can have as many PWM generators as will fit and you have pins for
2. If you are using STMBL drives, you dont need any PWM generators

Note that to use the 7I94 (without complaints from LinuxCNC about an unknown board)
you need to get some patches from Mesa and build LinuxCNC from scratch

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15 Oct 2019 15:36 #147935 by ross_dev
OK that sounds good, I think I will go for the 7i94 then. Thank you for your help!

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16 Oct 2019 10:50 - 16 Oct 2019 12:03 #147987 by ross_dev

Note that to use the 7I94 (without complaints from LinuxCNC about an unknown board)
you need to get some patches from Mesa and build LinuxCNC from scratch


Can you advise the usual method for getting hold of these patches? Checking the downloads section on the MESA site I can see a zip of the BIT files, but no link to patches etc. Happy to give them a call.

When it comes to the HAL file, are both hm2_eth and hostmot2 necessary? As the PWM is handled by the STMBLs, there is no need to pass pwm / stepper parameters? Is it worth trying PNCConf or will this lead me down a blind alley? I note for example using a 7i92 option, it only gives me 1 sserial port with 4 channels, where we have 5 drivers to control.

Alternatively could you point me to an example hal and ini file which uses the 7i94 already, so I can use that as a starting point?

Thanks for the ongoing support

RD
Last edit: 16 Oct 2019 12:03 by ross_dev. Reason: Extra information

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19 Oct 2019 01:07 #148258 by andypugh
You always need to loadrt hostmot2 before loadrt-ing any specific interface drivers, as hostmot2 sets up the necessary infrastructure for the cards and handles all the stuff that is common between them.

(note that hostmot2 is 1300 lines of code, hm2_pci is 650 lines of code, most of the work is done by hostmot2)
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