• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 81 subscribers
  • Views 1387 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

XRS (Reset) always held low - even with pull-up attached

Daniel Bland
Intellectual 465 points
Other Parts Discussed in Thread: CONTROLSUITE

I have a F2802x on a PCB which I can work with just fine via SCI_Boot.

I've now tried connecting a blank chip in a socket module.  I've connected 3.3V to VDDIO, all Vss to GND, and VREGENZ to GND.  VDDA is not connected.  I pull TRST and GPIO37 low and GPIO34 high.  I then pull XRS low for 50ms, then take it high.  This should make it boot in SCI_Boot (works on the PCB).

It wasn't working, so I connected a 2k2 resistor from XRS to 3.3V, and was very surprised to see it was still being pulled constantly low, around 0.1V.  This is obviously a problem, as the device won't start up if XRS is ALWAYS low.  It continues to do this if I remove my external system and just apply power to the Picollo.

Does anyone have any ideas on what I might be missing?  Do I HAVE to connect a crystal for proper operation?

I also noticed the voltage measured on the VDD pins (meant to be internally regulated) was 2.5V, their max rating.  I added 10uF from VDDIO to GND, this made it drop to 2.3V, still very high.  I am obviously doing something wrong.

  • 0
    Intellectual 465 points

    I tried adding a 16MHz crystal across X1 & X2, still no luck.  XRS is still low and VDD is "regulated" to 2.3V.

    I get tiny and very short spikes at 500Hz on the XRS line, but it always pulls it back to low ASAP.  I thought maybe a watchdog, but it should be disabled in SCI_Boot.

    Anyone have any other suggestions / reasons why this could be happening??

  • 0 in reply to Daniel Bland
    Intellectual 465 points

    It turns out the capacitors on the VDD lines are REALLY important.  Once I ensured the caps were very close to the pins and added a 10uF cap for each VDD pin, it all started to work.

  • 0 in reply to Daniel Bland
    TI__Guru 57255 points

    Daniel,

    Sorry for the delay.  I'm glad you were able to get it to work.  From the F28027 controlCARD schematics in controlSUITE (a good reference): C4, C5, R1, R2, and R14 are the most critical components.

    C:\TI\controlSUITE\development_kits\~controlCARDs\CC2802xHWdevPkg\


    Thank you,
    Brett