ncWriteMult sending rate & accuracy

[Julien C]

Hi,
I have troubles using NI-CAN v2.3 ncWriteMult function. I have to replay a log file containing CAN frames. The frames have to be sent approximately every 0.5ms at 500kbits/s. I use ncWriteMult and an array of 512 NCTYPE_CAN_STRUCT.
I use an CAN Network analyzer to check if frames are sent on the bus and actually all frames are transmitted but every 1.7 - 1.8ms at 500kbits/s.
If I use a file with 1ms separated frames the gap between them is still 1.7 -1.8ms.
I'd like to know if those values represent the best accuracy I can obtain with this ncWriteMult function. I am using a laptop with a PCMCIA-CAN/2 card.
Would the replay rate be better with a Series 2 card ?
Thanks.

[biker2000]

Hi Julien,

You are correct in your observation. 1.7 to 1.8 ms is the maximum rate with which the ncWriteNetMult() function can generate frames on the bus, when the Transmit Mode attribute is set to Timestamped Transmit (1, which is the preferred mode for replay type applications).
Changing the Transmit Mode to Immediate Transmit (0) allows for a much faster transmission of the data, however, the provided timestamps are no longer used for timing.

Unfortunately, this restriction also applies to Series 2 CAN hardware.

-B2k