On 7/7/2019 12:22 PM, justin White wrote: > I asked a similar question over on the LCNC forums and PCW confirmed it's > just straight RS-422. The 7i76 was probably a bad example, the LBP section > of the manual for the (e) version confirms what you said about it > communicating with it's own I/O section over SSerial, I just want to slap > the single SSerial channel on the board. Not sure about the termination > resistor, I usually see it suggested on the Rx line but the datasheet for > the transceiver I'm looking at suggests termination on the driver as well. > Any thoughts on the attached drawing?
There's good info in the data sheet for that part: http://www.ti.com/lit/gpn/thvd1451 ...which is an RS-485 transceiver (RS-485 is the same electrically as RS-422, but the driver can be switched off). RS-485 is a "multi-drop" protocol, and supports multiple transceivers. Typically, the end nodes will have termination resistors populated and the devices in the middle on the cable will have the termination disabled. See figure 32 (page 22) in the data sheet. PCW said it's straight RS-422, not RS-485. That means you only have two devices making each device an end point, so add termination to both ends. The ESD protection is application dependent, but you might also want a small value series resistor between the THVD1451 and the cable (see Figure 38, page 27 along with the recommend parts list) and see the layout recommendations on page 29. ...but don't sweat the details too much. For a short range (a few meters) point-to-point connection, the ESD and even the termination resistors are not super important. I'd still add them (it's cheap insurance!), but I don't expect you're designing for 1.5 km long cables that need to withstand nearby lightning strikes. :) That said, spindle motors can throw off enough ESD to cause problems even with differential signals, which is why you want _something_. -- Charles Steinkuehler [email protected] -- website: http://www.machinekit.io blog: http://blog.machinekit.io github: https://github.com/machinekit --- You received this message because you are subscribed to the Google Groups "Machinekit" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. Visit this group at https://groups.google.com/group/machinekit. To view this discussion on the web visit https://groups.google.com/d/msgid/machinekit/167de833-4ebe-6809-97aa-84ccfa4077e6%40steinkuehler.net. For more options, visit https://groups.google.com/d/optout.
