ESP8266 Community Forum

Under boards.txt, I saw this . Sometimes, it uses qio, sometimes dio. What is the difference between flash mode qio and dio?

Quad IO uses 4 lines for data for up to 4 times the speed of standard.
Dual IO uses 2 lines for data
Standard uses a single line for data

You need to use the mode that the flash part supports. The datasheet for the part should describe the modes that it supports. The HW design also has to have the lines connected.