The level shifter came in this week.
Populating the board:
I installed parts out of my kit in the order that I grabbed them, until I had enough to do the basic test. The board powered up and the blue LED on the ESP-12F blinked once. Unfortunately the board wouldn’t program.
I started probing with my Oscilloscope. The serial data lines looked normal when I tried to program the board. Then I looked at Reset and GPIO0 lines and found that GPIO0 was oscillating at 24 MHz. The Reset line was working as I expected it to. I used a 1 MOhm resister as a pull down on GPIO15. I chose 1 MOhm to reduce the amount of current when A_Sel is High. I knew this could cause me trouble, GPIO15 is used to put the chip into SD card mode. That may be too much resistance. I changed that resistor to 10 KOhms to see if it made a difference. It did!
I uploaded the defaults, then my code. My simple serial menu came up in the terminal. With it working, I went on to populate the rest of the board. I came up short 2 components, the pin header I use for the lithium cell and Q2. I grabbed both of those from the last build and completed populating the board. I reconnected it to my computer, re-connected the serial terminal and the serial menu is still working.
SPI RAM Testing:
I received the PCBs from PCBWay this week. I have not received the level shifter yet.
The new PCBs look good. Unfortunately the silkscreen part of my logo is not as crisp as I had hoped. The arrows still have too small of a gap and the silkscreen bridged together at one point. I still need to modify the logo.
Neither the PCBs or components have arrived yet.
This week I decided to work on the Vpp feedback loop. I am interested to see how well the system can regulate the boosted voltage operating on an interrupt driven control loop.
I needed to see if I could get reliable numbers back from the ADC while generating a given voltage. First step then was to make it so I could change the state of the analog switch from the serial console. I used the keys ‘<‘ and ‘>’ to select which input I would be connected to the ADC. I wasn’t sure which signal would be connected to the ADC, So I made sure I could select each one individually. Typing < into the console sets GPIO15 to low and typing > sets GPIO15 high. While setting this up, I discovered that GPIO2 wasn’t configured correctly like I had thought. I fixed this and added the little bit of code to give me control and tried it. It built and uploaded without a hitch.
The code was running, ready to test. I hooked up my oscilloscope to watch the output of the Vpp pin to compare to the analog readings. When first hooked up, the scope was reading 4.8V and the ADC gave me a result of 15. (ADC should give a result of approximately 230.) I hit the > to see and I got a result of 24. (off by a factor of 10). I decided to see if that would hold. I played with the Sigma delta till I got an output around 10 volts. I landed at 10.8V. At this voltage, the ADC result was 24(no change). This was disappointing. I hit the < key and read out the ADC with result of 20. Not what I was looking for. (expected something either twice the original value of 15 or 512) The results are not what I had expected(fail).