Designs

“To understand the magic of computing, look not at the towers of abstraction, but at the copper tracks connecting processor to memory.”

Sonoff MiniR2 Reprogramming

Notes on reprogramming the Sonoff MiniR2 controllers

The Sonoff MiniR2 is a versatile mains-powered device containing an Espressif ESP8285 (essentially an ESP8266 processor plus 1MB of built-in flash memory) along with a relay output, a switch input, and a spare GPIO input.

ESP/Arduino Date and Time

There's no need for a clock chip

The Arduino cores for the ESP8266 and ESP32 natively support the current date and time, synchronised to NTP servers. There is no need for a real-time clock chip or for extra libraries.

Timing Matters

Read/Write Timing - Poor design and a wasted gate

I sometimes see 8-bit CPU interfacing to memory using an output enable signal (OE) to the memory device that is generated by combining (NANDing) the read/write (R/W) line with the CPU enable (E), as shown above, in a similar way to the write enable signal (WE). This is poor design and should be avoided.