please name the i2c devices you have tested or using

• FM Radio module RDA5807M
  
• On an ESP8266-12F
  
• Using I2C1.setup({sda: D4, scl: D5});
  
• NOT working :(
  
  

Works fine in Mongoose IoT (formerly smart.js)

Will try to build the mentioned clock stretching code soon to see if that can make it work.