Updating Schematic V00B

In the last few posts, I found several problems with the design as well as found some ways to reduce Bill of Material costs.  I also want to make soldering of the parts easier for a hobbyist.

I had problems using the CH340G chip on my NodeMCU board.  I couldn’t find any references to this problem on the internet.  So I replaced U8 (the CP2104 USB to UART bridge) with the CH340G USB to UART bridge.  I inverted DTR and RTS  and connected them to GPIO0 and RST respectively.  Using transistors as the inverters means that when U8 is not powered, it won’t draw those two lines down.  This is looking forward to when the design is battery powered.

I used the NodeMCU schematic as reference during this part of the design since it is close to what I want to do with this part of the design.

I changed the reset push-button switch to pads on the board and left the upload push-button switch unchanged but don’t plan on installing it unless I run into problems programming the board.

I also want to make things smaller, U9 is a large part of the board.  A shift register can do the same thing and be less expensive. I found the 74HC595 to replace U9. I am still clocking data in using the SPI bus, and then latching it with a pulse from GPIO5.

For the High voltage, I removed the AAT1230 and replaced it with two logic level FETs. One to disable the circuit to drop current draw when in low power mode connected to GPIO14. The other the pulse stream that generates the current through the inductor connected to GPIO4.  This means all the pins on the module are used up again.

Kicad schematic and layout can now be found here. The pcb layout is not current to the schematic, I still need to do a design review before I start the layout.

UProgrammerSchV00B

Associating parts to pinouts

I ran the annotate schematic tool, then ERC to look for obvious mistakes.

I got a bunch of errors because I had left pins unconnected.  This is a reminder that I have to make sure these pins are set to outputs later.  I marked each unconnected pin with a no connect marker and I am down to 3 errors. I replaced the battery connector with a battery symbol.  It didn’t get rid of the error, I will have to check this connection on the netlist.

I then ran the netlist tool with default settings.

Then I ran the CvPCB module of KiCAD. I assigned footprints to the parts from the schematic.  Most of these matched.  For resistors and capacitors, I chose to use 1206 SMD for the footprints.  There is no footprint for the ESP-12E.

I found a footprint online for the module, but KiCAD would not import it. So, I created a footprint and added it to the custom library for the project.

I chose the SW_PUSH_SMALL for the two tactile switches Reset and Upload.  These are through hole footprints, I am thinking I will copy this footprint to the custom library and modify it to go surface mount.

I have only done very simple layouts.  This will be quite a learning experience for me.

CvPCB 1st