Debugging Guide

You're here because your board isn't working.

No matter! Debugging is a part of the engineering process and you will get that practice through practicums.

First, is your power on?

Seems obvious, but make sure you check the power supply is on and at the correct voltage. If you're using both the 6V and 20V switch between the knobs to make sure they're all on.

Next, are any of your wires touching? This could cause major problems, so be careful and take the extra time to have a neat set up and strip your wires correctly.

The main reason your board is likely not working is that a signal or power supply is not reaching its intended pin. To debug, you are looking for where this signal breaks.

The first place to look is your solder joints. Inspect them and redo any ones that seem incomplete. Here's an image to remind you of properly done solder joints.

Another issue is if you put too much solder on, two pins can be connected (see Figure 1, E). You can check that by using the connectivity option again on the multimeter. There should be no beep to indicate the pins are not connected. If there is a beep, you will have to desolder. Ask a professor or proctor for help on this.

If redoing solder joints doesn't solve your problem, or your solder joints look correct, then you will start checking connectivity.

You can continue to test the signal's path by texting for connectivity between the two PRES pins on your board, or a PRES pin on your main board and the PRES on your breakout board to test the connectivity through the ribbon cable.

Testing connectivity throughout the trace of a signal is the best way to tell whether there are faulty solder joints. See Figure 3 to see possible connectivity test points.

See Figure 4 for a schematic of your board for another way to visualize which pins are connected.

You can also check for known voltages at different points on the board. If you are not getting a voltage you expect, there is likely a break in the signal's path from a weak solder joint.

Power your circuit board between 5V and AGND using setups similar to those from Practicums 2A or 2C (i.e. use breakout boards or jumper cables to connect to the 5V and AGND pins).

P_SENSE should have a voltage of about 0.8V when the pressure tube is in the air (0m depth). Test this with the probe at P_SENSE and the ground clip at ground.

PRES (on the breakout board) should have a voltage of about 1.3-1.6V when the pressure tube is still in the air. Test this with the probe at PRES and the ground clip at ground.

T_SENSE and TEMP should have about the same voltage but this depends on what you chose for your mystery resistor. For 20.3 C, both pins read about 4.2-4.3V. ****

To troubleshoot your motor, you can use the setup from Practicum 2C and set your scope to the settings in Figure 4. The green waveform is from connecting an oscilloscope channel to the wave generator output. You should put the positive end of the WaveGen into 1A and the ground into 2A.

Using these settings, you should get about 2.5V when measuring the voltage between 1A and 2A using a multimeter and about 2.2V between 1Y and 2Y when the motor isn't connected (make sure the multimeter is in AC mode, not DC mode). Note that since you are putting a PWM through 1A and 2A, these voltages off the multimeter are some average value between the low and high level of the square wave.

If you are not getting these voltage measurements (1A/2A and 1Y/2Y) check the solder joints along this trace.

If these methods do not alleviate issues with your board, call a professor or proctor to help troubleshoot.