Testing your board

Once the surface mount components of the base board are installed, preliminary testing can begin.

It is easiest to do this testing before installing the through hole headers as they can get in the way of making measurements.


First Step:

Using a USB charger cable as for a cell phone or other USB device connect to power the SMT Workshop board.   Do not just plug into a computer first to power the board, as a failure in assembly could cause damage to the computer.

With the USB power cord connected, the 3V and 5V LEDs should illuminate.  This is great! and means that the power supply section of your board is at least 50% working.  Use a volt meter to measure the 5V and 3V voltages.  There are several points a ground reference can be found on the board.  The 3V and 5V rail voltages can be measured on the connector below the processor.

If the LEDs fail to illuminate the first thing to check is that you did the ECO (engineering change order) and reversed the direction of the 3 diodes, D3, D4 and D5 in the power supply.  Check that F1 is installed.  Double check that the USB port is properly soldered down, and that there are no solder bridges between the pins.  Solder bridges between the pins on the 3V regulator U2 can also cause the supply to not function.

Next, measure the voltages on the 5V and 3V pins of the power connector below the processor anyhow.  You may have installed the LEDs backwards.

If the 5V LED illuminates but the 3V does not, check your soldering around the 3V regulator U2.  It is small and can be difficult not to short pins.

Step 2:

Remove the USB power, and plug in a 6V to 12V DC power supply to the barrel jack, J12.

Again the 5V and 3V LEDs should illuminate and they should be the same brightness as before.

Congratulations your power supply is working!


Step 3:

Removing the DC power supply, plug the board into a computer via the USB cable.

The computer should recognize that a new USB device has been connected.

If so congratulations again, your SMT-Workshop board is ready to have the remainder of the components installed!


If the board does not enumerate to the computer, that indicates a problem with the soldering of either the microcontroller, or the crystal.  Visually inspect all the pins of the microcontroller that there are no solder bridges or missing solder, and that the chip is in the proper orientation.  The pin one marker, little circular indentation, should be pointing at the reference designator U4.

When the microcontroller soldering and orientation have been verified, next to check is the crystal.  Because of the physical construction of the crystal it is very difficult to visually identify a soldering fault.  It is best to resolder all four corners, using a large tip.  Leaving the tip on each corner long enough for the solder to fully melt all the way under the crystals package.

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