Tech Diary

This post describes the control panel developed with a few open source software and libraries. The main purpose is to have a proof of concept that the various components can be put together to become a useful product. I have built a smart home system controlled using Openhab and the hardware switches are primarily using Sonoff switches with Tasmota firmware. The switches are controlled using Openhab Habpanel using an Android Tablet. Generally, this is my preferred way of  using the Android Tablet but the Arduino control panel is developed so that it can interface to external hardware at low cost. The control panel is developed using ESP-Link firmware with the El-client APIs and the hardware is an ESP8266 and Mega2560 combi board.  Besides acting as a touchscreen based on/off switch, it is also an internet clock (ntp) and a doorbell buzzer. The software/firmware/libraries are ESP-Link el-client APIs (interface to ESP-Link firmware MCUFriends Arduino library...

I have found this interesting board selling on Aliexpress website. It is an Arduino Mega 2650 with a built-in ESP8266 which allows the Mega to connect to wifi. This board has cut down a lot of wiring and bring out interesting possibilities. One of this is to connect up both the microcontrollers using ESP-link firmware. I have an earlier blog post  that described how to wire up an ESP-01 and Arduino Pro Mini. One of the tricky parts in this setup is the sequence of flashing the ESP firmware. Flashing the onboard ESP8266 requires some setting changes to the dip switches. The following are the sequences which I get both the microcontrollers to talk to each other. Set the jumper 5,6,7 to ON and the rest OFF. This will set the ESP to update mode. I am using version 3.0.14  and flashed the ESP using the following parameters: esptool --port com26 --baud 230400 write_flash -fm dio -fs 4MB -ff 80m 0x0 boot_v1.6.bin 0x1000 user1.bin 0x3fc000 esp_init_data_defa...

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...