How to use FTC hi-tech motor controllor on FRC

[FTC5110]

Best guess is your I2C clock is too fast and perhaps other timing issues. At a guess I'd say the I2C implementation on the HiTechnic controllers may well be software based and perhaps less able to handle higher clock frequencies or shorter setup times.

In the Arduino trace you can see the SDA change state right around the time SCL goes low. cRIO has SCL low before SDA changes state and then SCL high pretty soon afterwards. Granted it should be clocked on SCL going high so shouldn't make any difference but worth pointing out.

The NAK is because the I2C slave didn't respond. Arduino gets an ACK, cRIO gets a NAK (i.e. slave didn't hear you).

If the cRIO has some way to change I2C clock to 9600 which the NXT uses then perhaps it might work better however the asymetric clock and slightly delayed SDA setup might be fatal to HiTechnic controllers.