A blog post by Steve Sakoman here inspired me to make up my own Thumbo and Pinto-TH equipped breadboards. All the credit of showing how to create a serial console with these boards belongs to him. In the photos shown below, I simply duplicate his work. As you can see from the blog comments, Steve answered my questions as I assembled these circuits and progressed. Thanks, Steve!
What I now have is two different expansion boards properly set up so I can access the signals generated by the Overo.
This photo shows my Thumbo expansion board booting with an Overo Water computer-on-module (COM) board installed. The Water board is booting from NAND; no micro-SD card is installed. Serial console access is provided by use of an FTDI cable. The part number is TTL-232RG-VREG1V8-WE "USB to TTL Serial Cable-1.8m Wire End Version". I have soldered 6" pins onto the wire ends. Only the GND, RXD and TXD pins are connected to the circuit. The other FTDI pins are tucked out of the way and not connected to anything in this photo.
Close up shot of the FTDI cable's connections to the Thumbo board. As you can see, it is quite simple.
Another view of the board. This photo shows the circuit more fully. The red board at left is a 3.3v/5v power supply board from Sparkfun.com and supplies 5v to the Thumbo. You can see the FTDI cable connections now. Unused connections are tucked out of the way to the right and are not connected to the circuit. The breadboard is an old Global Specialties PB-102. The two LEDs are just "pilot lights" to show that power is present on the supply rails. This board will soon be populated with a 7-segment LCD display as I try a new mini-project from Steve Sakoman's site.
This photo shows my Pinto-TH booting with an Overo Water board installed. The text callouts on the photo identify the parts. The FTDI board, level translator and power supply board are all from Sparkfun.com.
Here we can see the resulting console.
This photo of my Pinto-TH board shows the wiring a little more clearly: