blippy wrote: ↑
Fri Feb 16, 2018 7:36 pm
Am I right in thinking that all the GPIO pins are 3.3V tolerant, but not 5V tolerant?
If so, isn't the 5V GPIO inviting a lot of trouble?
For example, the blinkt uses the 5V pin. How comes it doesn't cause damage to the other pins that it uses for SPI communication? Does the blinkt have a built-in voltage divider for example?
Or it is that the voltage on the SPI lines is pulled up to 3.3V by the Pi, which is then only ever grounded?
It seems that there are lots of opportunities to fry you pins if you try to connect two devices together for the purposes of communication over, say, SPI or I2C. And how do you work out what the line voltage is
The 5V "GPIO" is not a (SoC) GPIO connection it's the 5V power connection. To put it another way - when referring to "GPIO voltage levels" one is not
referring to the GPIO connector pins
but to the GPIO ports of the SoC
to which some, but not all
, of the connector pins are physically connected**. So "Am I right in thinking that all the GPIO pins are 3.3V tolerant, but not 5V tolerant?" is incorrect but, yes, the SoC GPIO ports that are
connected to some of those pins are not
5V tolerant. Of course some of the connector pins are connected to GrouND (0V), common to the 5V & 3.3V power supply and the 3.3V GPIO signals. What is "the blinkt"? (link/picture perhaps?). W.r.t. "It seems that there are lots of opportunities to fry you pins if you try to connect two devices together for the purposes of communication over, say, SPI or I2C. And how do you work out what the line voltage is" - that's why datasheets exist and need to be read & understood.
** Some of the SoC's GPIO ports are used to control other devices on the Pi's PCB and are thus not available for external use.
Still running Raspbian Jessie or Stretch on some older Pi's (an A, B1, 2xB2, B+, P2B, 3xP0, P0W, 2xP3A+, P3B+, P3B, B+, and a A+) but Buster on the P4B's. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm