ESP8266 Community Forum

- Sat Aug 20, 2016 11:42 am #53395 Dear Friends

i have bought an IOT board and wanted to use the spi pins of the e12

but i cant see any SDA pin nor SCL

i can see MOSI and MISO, RST, CO, MO, EN, SK, TX, RX AC, A0

so can any one tell me which is the SDA, SCK, MOSI, MISO, RST

- Sat Aug 20, 2016 12:37 pm #53405 SDA/SCL pins are I2C pins (not SPI), and since the I2C is bit-banging done in software, it can use any GPIOs simply by providing their number in Wire.begin(0, 2), for example, it would be GPIO0/GPIO2.

- Sat Aug 20, 2016 4:49 pm #53434

SDA/SCL pins are I2C pins (not SPI), and since the I2C is bit-banging done in software, it can use any GPIOs simply by providing their number in Wire.begin(0, 2), for example, it would be GPIO0/GPIO2.

dear friend i am asking this because i am using MFRC522 rfid module
so i don't know really where to connect these.

- Sun Aug 21, 2016 7:56 am #53481 Ok ! The MFR522 can be connected in 3 modes : I2C, UART or SPI modes.
Some of the pins are shared between mode, like like the SDA of I2C mode is named SS in SPI mode, as well SCL of I2C mode is named MISO in SPI mode.
The selection of the mode depends on I2C pins 1 of the chip itself. Maybe some board provide access to it, but most are not providing it, therefore probably hard-wired into SPI mode.

For SPI mode, someone already port a library for ESP8266 :
https://github.com/Jorgen-VikingGod/ESP8266-MFRC522