NI 9860 and LIN Interface Power

[Hooovahh]

I've recently started using the C-series module NI 9860 which is a neat little hardware configurable XNet device.  This is great alternative to the other C-series XNet hardware which only has one port, and it is either dual wire CAN or LIN.  This can be two CAN, or two LIN, or one of each. (and maybe single wire CAN in the future? Hint, Hint, NI)

Now the reason for this post is because I'm using the LIN transceiver, and the card itself needs to be powered.  But when I use the LIN interface it also needs to be powered.  Is there a reason for this?  Can't NI just wire the power from Vsup internally to the DB9 interface?  And furthermore whey is VSup even needed?

I'm using a RT CDAQ chassis and I need to provide power to it (9-30VDC).  I then need to wire this same power to the VSup terminal (9-30VDC) on the input of the card.  AND I need to wire this same power to pins 9 and 3 of the DB9 of the LIN interface (8-18VDC).  What's the point of all of this?  Can't the card be powered by the chassis?  Can't the transceiver be powered by the card?  If anyone else uses LIN on the 9860 just know you need to power both the card and transceiver, (and the chassis if applicable) and they can be from the same supply.

[GerdW · Accepted solution]

Hi Hooovahh,

this is something that also bugs me since NI dropped support for "two port PCMCIA CAN cards"…

To my understanding I would give such answers:

- the module needs to be powered externally due to it's power demands. It needs more power than is supplied by the cDAQ chassis. (As written in the specs it draws <1W from chassis and <1.5W from external supply.)

- the LIN port usually is a "single wire" interface, with additional voltage reference to an (external) power supply. In cars this tends to be the battery, so the LIN "cable" has three wires: GND, LIN-signal and 12V battery supply. You need this external power supply as all devices on the LIN bus reference their voltage levels with respect to that power supply!

[GiantDeathRobot]

Hi guys,

I believe GerdW is right on both counts. From my understanding of the 9860, some of the circuitry on the transceiver side is powered externally, so the external power is required.

LIN uses Vsup as a reference for the LIN line. As Hooovahh mentioned, Vsup needs to come from somewhere. It can be directly supplied to the bus from a battery or some such, or come from a LIN device. This isn't required in a LIN device, so some of our devices don't require external power (the NI 9866, for instance) while other devices are designed to provide power to the bus. The 9860 falls into the second class.

That said, if I recall, the controller should be powered from the chassis power rail, and the transceiver and bus should be powered from the module's external power connection. I believe the 9860 regulates the external power, and routes it out to the Vsup and COM lines of the DB9 connector internally. Hope that clears things up!