I got the revised boards and finally found some time to assemble a board. This board adds a logic inverter to fix the flow control, and removes some extra traces for an alternate reset circuit.
To assemble the board, I had a stencil made and used it to apply solder paste. Then I placed the components using a very simple “pick and place” rig:
This jig was made from a piece of brass tube, a leur lock fitting, some tubing, and a 22ga blunt dispensing needle. It was mounted in a cheap USB microscope holder (available on eBay or Amazon) and hooked to a vacuum pump that I already had. There are many more complicated versions of this rig on the internet, but this simple setup worked fine for me.
Finally, I baked it in a toaster oven that I got for free at a garage sale, and a rocket scream reflow shield.
Everything works great. I consider this project a success. All thats left to do now is to 3D print a replacement for the plastic “plug” that covers the hole in the case.
Finally, a little application that uses the method mentioned in an earlier post to enable the board when the ‘modem’ port is opened:
