So today I added the resistors and once again held my breath and attempted to access the SD card on my FujiNet device - No dice still not working. It was wishful thinking that it would, but with other people's units working without pull-ups, I wasn't surprised. No matter, the pull-up resistors will still be added in my design.
Next I re-flowed the solder at the ESP32 connections, but that also failed to correct the situation. When probing the signal lines with a scope I saw no activity, and the CS line remained high, which is the normal idle state. It's almost like there's no one awake inside.
At this point I can only surmise that my ESP32 possibly has at least one I/O pin that is damaged. And since it's not easy to replace, I'll be looking at a 2nd build with a fresh board and new parts.
In the meantime I've been fine tuning the design, and moved it up to Version 1.2.
Here's the Updated Schematic (3-9-2021)
showing changes to come.
Another thing I discovered, was that the information I had gotten for my USB/Serial cable was incorrect, which was why I thought I needed to swap the RX and TX pins. So that's been restored to the way it was shown in the very first schematic, matching the prototype PCB that was based upon that.
Next I really didn't like where the ADC VREF voltage divider was getting its positive voltage from (SIO), so I moved it over to the regulated 3.3V bus... EDIT: I totally misunderstood the purpose of the voltage divider. In actuality it is being used to sense voltage coming from the Atari in order to determine if it's powered ON or OFF. The voltage divider simply brings the 5V of the Atari down to a level that's safe for the ESP32 to look at by one of its ADC inputs. So I have restored the original voltage divider in my schematic and renamed the wire label as VSENSE instead of VREF. The schematic download has been updated with this change.
I also decided to reduce the size of the programming header, as well as eliminate the SIO-Thru header and only pass along the PS/2 and power related signals via a 5-pin header. The PS/2 connections are present in case I wish to develop an active Wireless USB to PS/2 converter, which is something that is definitely on my wish list.
And for the final touch, the resistor array has been expanded to include the three SD related signals, thus actively pulling them up to 3.3V.
Hopefully the next time I write about this specific FujiNet prototype it will be to discuss the successful operation of the SD card.