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268TMS470R1A256 + MC33390?

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  • Scott Coleman
    Jul 6 9:26 PM
      Have any of you tried to interface a MC33390 J-1850 driver chip to a TMS470? Were you successful?

      From looking at the datasheet


      it looks as though this part was designed to interface with micros that have 5V TTL I/O. Just for snicks I built a circuit anyway, and connected it to my Olimex TMS470-P256 development board. The RX data output line from the MC33390 has a high logic level of 4V; this doesn't seem to sit too well with the 3.3V input of the TMS470R1A256, as messages are only received intermittently. When looking at the J-1850 bus output with a scope, the output voltage also toggles between ~0V and ~4V (the high level should me closer to 7V).

      If other driver chips, such as the NXP AU5783, were still available, I'd just use one of them and be done with it. Unfortunately, J-1850 seems to be a technology that's fading into the sunset; most of the driver chips are no longer being produced. The MC33390 appears to be the last of a dying breed. I may be stuck trying to make this work (or resorting to a bit-banged solution, which would be a major PITA).

      Anyway, I'm hoping someone out there is using this chip successfully and will give me some guidance.

      Thanks for your help!