A few months ago, I started working on an MCU Card design, which borrows from the idea of a standard desktop PC, in which there are a main-board, MCU and expansion slots, to add and remove peripherals as needed quickly.
The ESP-12E Card is a continuation of that project, with the ultimate goal to have a universal “main-board” that can accept various MCUs and standardised “expansion modules” that perform a specific task.
The ESP-12E Card contains the bare minimum components to allow the chip to function. There are no power regulators or USB-to-TTL converters onboard. Code is flashed via an external USB-to-TTL converter, with Flash and Reset buttons on the actual PCB, or available in the 2×20 Pin female header at the bottom of the card.
Most of the GPIO is also broken out to the 2×20 pin header, with the exception of the 6 GPIO that is usually connected to the internal Flash on the ESP-12E module.
I have made provision for enough power and ground pins on the header as well.
As far as GPIO is concerned, They have been grouped together by function, as much as possible at least, to make interfacing with the base-board as easy as possible.
The schematic is not complicated. It is a standard ESP-8266 configuration, with all non-essential components removed.
The “base-board” ( a sneak preview )
In a future article, I will tell you more about this ( for the time being limited to I2C ) base card. [ a quick explanation: When I mean limited to I2C, it relates to the fact that at the moment, the base card, ( a prototype ) can only communicate back to the MCU via I2C protocol from each of the expansion slots, as well as via two dedicated IRQ lines from each slot ]Power is supplied via a small SMPS module.
Manufacturing the PCB
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