Tech Diary

ESP-01 is a simple ESP8266 module which can be purchased cheaply from Aliexpress. At one of promotion, I purchased an ESP-01 for just S$1.97. That's very cheap for a wifi enabled microcontroller. An ESP-01 can be a WIFI bridge for non-connected microcontroller such as Arduino UNO, Mega, Nano etc. Communication between the microcontroller can be done using the serial link between them. I have written a post on this using ESP-Link to connect to an Arduino Pro Mini. Together with the client library provided, the Pro Mini can easily transfer sensor data via MQTT. http://iotdiary.blogspot.sg/2017/09/using-esp-link-transparent-bridge.html For the most part, once the firmware is in place, normally I will use OTA to update. Sometimes, I wanted to reuse the same controller for another firmware and I have rewired up the controller for reflashing. This makes it very inconvenient to use. Recently, I bought a USB ESP-01 adapter thinking that my problem is solved. When I received it and r...

Recently stumbled across an interesting open source project ESP-Link . Its main purpose is to network-enable a non-network microcontroller (MCU) such as Arduino Uno, Pro mini or Nano using ESP8266. The author termed it as "Transparent Bridge". The ESP and MCU  communicate via the serial link and there is a companion Arduino library EL-Client  for the MCU to connect up the network using MQTT, REST, TCP and UDP. Setup I have put together an ESP-01 and an Arduino Pro Mini for this experiment. I have chosen a 3.3 version Pro mini so that I do not need to do any voltage level shifting between the I/O pins. In order to have a stable voltage source, the ESP8266 is powered by Pro Mini and the Pro Mini "RAW" pin is connected to a 5v USB power source. The RAW pin can take voltage up to 12V. The reset pin of Pro Mini is connected to GPIO 0 of ESP-01. This enables the ESP-01 to reset the Pro Mini.   I have linked up an APDS 9960 sensor to it and periodically se...