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No output from pins

Other Parts Discussed in Thread: ENERGIA

I am using a TivaC connected launchpad to program a breakout board with a TM4C1294NCDPT chip.  I am successfully able to flash it using LM Flash Programmer using *.bin files compiled from energia.  I have tried the first pin PD_0 and a few others like PN_0 and PF_4 but none of them would provide any output when set high.  I have tested the code on a connected launchpad and the code does work.

 

All the VDD, VDDC, GND, and pull up resistors are connected accordingly just like shown in the launchpad.  I have tried to add a 16Mhz crystal but it does not appear to make a difference.

 

Flashing always requires us to go through the Debug Port Unlock process.

 

After a few attempts, it wont go into the debug mode in Keil IDE anymore.

The chip and LP are isolated by removing the JTAG pins going to the launchpad so that the only thing connected to the chip is the 3.3v power and ground from the launchpad.  The pins that should go high only outputs 0.645V while on the launchpad it would have 3.3v.  We even used a hot air station to completely desolder a programmed TM4C1294 chip from the launchpad and resoldered it onto one of the breakout boards and only provide power but it still doesn't work.

 

When flashing the LM Flash programmer verified the memory and did a hardware reset and it still doesn't work.

 

Is the 25Mhz crystal required for the chip to be operational?  Also, is the 6mm distance max between the crystal and pin absolutely necessary?

 

Here is the sketch I used to test the pins using energia.

  1. void setup() {
  2. pinMode(PD_0, OUTPUT);
  3. pinMode(PN_0, OUTPUT);
  4. pinMode(PF_4, OUTPUT);
  5. }
  6. void loop() {
  7. digitalWrite(PD_0, HIGH);
  8. digitalWrite(PN_0, HIGH);
  9. digitalWrite(PF_4, HIGH);
  10. delay(1000);
  11. digitalWrite(PD_0, LOW);
  12. digitalWrite(PN_0, LOW);
  13. digitalWrite(PF_4, LOW);
  14. delay(1000);
  15. }

  • Hello Dennis,


    25MHz is only required for ethernet operation. It is not mandatory otherwise. Also crystal must be kept as close as possible to the device.
    Looks like there is an issue on your breakout board since a programmed device does not work. Have you checked if the supply is sourcing enough current for the device to work. Also can you share the schematics (and let us know what is populated and what is not)

    Regards
    Amit
  • Hi Dennis,

    You can ignore the 16Mhz crystal (you can use the PIOSC instead of the main oscilator) if I am not mistaken.

    What is your circuit for the break out board? Your probably missing some capacitors or registers I would check this out:
    tec.icbuy.com/.../spma051.pdf
    It should also inform you about the need for external crystals
  • The VDD are connected to the 3.3v on the launchpad and i have 4 0.1uF caps on the 3.3v to GND.  VDDC has a 0.1uF, 1uF, and 2.2uF cap going to GND.  VREFA+ and VDDA goes to VDD.  All the VDD, VDDC, GND, RBIAS pins are connected on the chip.  I have 4.87k but it is 5% tolerance.  XOSC0, XOSC1, OSC0, OSC1 are connected to GND.

    This is the breakout board I am using. 

    Schematic

    7416.TivaC.pdf

  • The VDD are connected to the 3.3v on the launchpad and i have 4 0.1uF caps on the 3.3v to GND.  VDDC has a 0.1uF, 1uF, and 2.2uF cap going to GND.  VREFA+ and VDDA goes to VDD.  All the VDD, VDDC, GND, RBIAS pins are connected on the chip.  I have 4.87k but it is 5% tolerance.  XOSC0, XOSC1, OSC0, OSC1 are connected to GND.

    This is the breakout board I am using. http://www.proto-advantage.com/store/product_info.php?products_id=2600014

    Schematic:

    1586.TivaC.pdf

  • In the schematic, I wasn't sure whether to use pull up or pull down for the JTAG pins so i placed resistors in there as a place holder. I didn't use all the resistors, i only used the pull up resistors when connected to the launchpad as shown in the launchpad schematic for testing using the breakout board. Same with the crystals, I was not sure at the time if it was necessary to even have a crystal for my project so i added it in anyways in the schematic.
  • Hello Dennis,

    Can you check on a scope if the VDDC is at 1.2V and VDD-VDDA at 3.3 V during the operation. Also is there a pull up/down on the board? Can you check what is the Resistance of the probe? Sometime back one of my colleagues measured 2.2V and it turned out to be a R-divider of 2/3 which causes a faulty measurement.

    Regards
    Amit