hello all, can you pls tell me maximum how many devices can be connected to controller using SPI? like in i2c maximum devices are 128. so pls tell me the number and how? thank you regards
No we can't. Why? Because there is no magically "correct" figure.
I2C contains addressing, so the figure you have seen relates to addressing of devices.
SPI uses separate signals for slave-select. If you use 4 slave-select lines you can address four slaves. If you use 19 slave-select pins you can address 19 slaves.
If you only send data in one direction - master-to-slave - you can have multiple SPI slaves connected and addressed at the same time using a single slave-select line.
In the end, the number of slaves possible depends on two things: - how much hardware you can dedicate to the addressing of the slaves - how much capacitance you have on the signals and your used bit rate - i.e. what load you can put on the signal wires and still maintain the required signal integrity.
You have read up on SPI before you did ask your question, haven't you?
hello sir, thanks for reply. i read SPI document and i knew that depending upon NSS lines slaves are interfaced. but i wanted to confirm and have other opinions of people and it is not mentioned in document clearly about salve numbers. anyways, thanks for your instant reply and clearing my doubts