Debugging

Tigard has 3 LEDs that should help in debugging issues with Tigard itself. A video demonstration is in progress, in the mean time, see these details from the Tigard Documentation. Once you know that Tigard is working as expected, it’s time to debug your protocol. The LA port discussed in the next section is very helpful in this case

PWR LED:

This will turn on when the board has USB power and should turn on immediately when the USB cable is connected.

  • If it does not, then check your USB cable and power supply.
  • If it comes on then goes off, is dim, or flickers, then you have likely shorted power or ground somewhere with your wires or your target.

EN LED:

This will turn on when the FTDI chip is operation and should turn on a moment after the usb power LED is on.

  • If it does not come on, you may have a faulty USB cable, a power-only USB port or cable, or a bad FTDI chip

VTGT LED:

This will turn on when the level shifters are properly powered, either by your target or by the onboard level selector

  • If you are in VTGT mode, and it does not come on, check your target power and your power and ground wiring to the target
  • If you are selecting a voltage and it does not come on, you have likely shorted power or ground somewhere with your wires or target.
  • There are corner cases where VTGT will get latched to a voltage applied to an output pin. Establishing a habit of always starting with VTGT off will help avoid this.

ALL LEDS ON:

When all LEDS are on, then Tigard is probably working as intended. If you are still having trouble, there are a few possibilities. They are listed in order of likelihood, though it makes sense to test the easier cases first:

  • It’s a wiring issure. Make sure your wires are connected well. Confirm with a multimeter.
  • It’s a target issue. Try a different target to make sure your software is working properly
  • It’s a software issue. Try a different software tool or mode to make sure your board works properly
  • It’s a protocol issue. Observe your signals with a logic analyzer or oscilloscope to make sure they’re correct
  • It’s a hardware issue. Try a different Tigard board to see if it persists
  • It’s a tigard issue. Try a different x232H board to see if it persists
Previous Lesson
Back to Course
Next Lesson