I'm looking at the connections between an Arduino/ESP32 board and an SPI Epaper screen from Waveshare.
Your answer is only a Google search away (BTW, you forgot the link to the used hardware). The wiki page for your display explains everything.
The busy signal is an output which tells the microcontroller that the display is busy and cannot react to commands....
An ESP32 board is not an Arduino, so the connections have to be adapted if you use an ESP board.
The question was on BUSY line generically, for a display, a keyboard or whatever.
There is no generic definition or function for BUSY pin on an SPI device, its on a case by case basis depending on the device. Read the device datasheet for details. There are SPI devices that can be 'BUSY' doing stuff and the only way you can work out if they are 'BUSY' is by polling registers over SPI interface to the device.
There is no definition of a 'busy' pin in the SPI interface so you cannot 'generalize' what this pin might exactly be be used for or indicate on a specific device and thus have a standard answer on how or what to connect it to. You need to study the documentation for the device you have and its library to work out how to connect your particular example of a 'busy' pin.
Ok but if in the documentation there is the indication for pin 7 that is referring to a lot of uses (just an example) how can I know if the pin 8 is as good as the 7.I mean it should be just a digital pin or it needs like RST, MOSI etc that can't be redirected?
I cannot say, it depends entirely on what the display does and used the Busy pin for. You will need to study the device datasheet, this is the third time I have mentioned it.
// Pin definition#define RST_PIN 8#define DC_PIN 9#define CS_PIN 10#define BUSY_PIN 7
The BUSY pin is defined in the library file epdif.hCode: [Select]// Pin definition#define RST_PIN 8#define DC_PIN 9#define CS_PIN 10#define BUSY_PIN 7You can change it to another pin, if you wish, as long as it doesn't conflict with the other pins used by the library and by the SPI hardware (pins 11,12,13).So, in particular, you can't use pin 8 instead of pin 7 because it is already used for RST_PIN. But you could use pin 6 or pin 5.Pete