RN-42-HID Bluetooth Breakout PCB Design Assistance

Projects General Guidance
1

I am new to PCB design and wanted to try it out. I created a simple breakout board for the RN-42-HID by (former) Roving Networks. I have the most recent datasheet, gerber files, and pictures of my schematic and board design included. I can't get the thing to work. The LED's don't light up, it doesn't respond to serial commands, I get nothing.

I have checked and rechecked, but as far as I can tell I am not missing anything. Does anyone here see any issues with the PCB I designed?

RN-42-HID.zip (775 KB)

2

This is a logic problem, you have to isolate where the error is. Is it a software error, a hardware error or what? Since hardware can be easier to test definitely, I usually check the hardware first. First thing I would check is to make sure that your ground and power connections are working properly. It's the quickest and easiest thing to check so I do this first. After I have ensured that they are working, using a multimeter I would work backwards from the LED to the device.

  1. Check continuity between the ground of R2 and the ground pin. If there is not continuity, then the problem is obvious.
  2. Check the resistance between across the resistor (measuring from the LED to the ground pin). This will rule out a mislabeled resistor. This is to check for mislabeled resistors, it does happen from time to time.
  3. Check the voltage across the LED (put the test leads on either side of the LED). This will let you know if any current is flowing across the LED. If the value is a fraction of a volt or zero, either the device can't supply enough current, the voltage is too low in combination with the resistor or the LED is dead.
  4. Check the voltages from the pin of the bluetooth device to the ground pin. If the device can't supply enough current, this will read low. If there is some sort of error with the device, then the value will read zero or close too it (some circuits can feed a few hundred millivolts or less to the outputs when turned off).

I noticed that the datasheet has a rather cryptic comment about the I/O pins being capable of 1uA which is WAY too low to drive an LED. Though their reference schematic shows LEDs connected to specific pins. Not sure which is right. Hopefully this helps you on the way to go.

3

This one is on me. I apparently read a bad guide online and was misinformed about SMD LED direction. I managed to fix the LED. As for the commands, I didn't switch the serial monitor to end commands with a newline. After the switch it worked fine.

My design wasn't flawed, I just made two blunders that lead to a lot of confusion.