Hey,
I have spent the last hours trying to understanding the I2C concept on the CM4. In the follwing I will summarize my findings and my remaining questions, grouped by I2C bus. I would be happy if somebody could help answer the questions and correct me, if some findings are wrong.
I2C0
Owned by the VPU/Firmware by default
- Does this cause problems? Can the bus be used normally (if i2c_vc=on is NOT set in config.txt)?
Can be muxed between GPIO0/1, GPIO28/29 and GPIO44/45
- Muxing is activated by setting i2c_vc=on in config.txt or by enabling i2c0if and i2c0mux in a DTOverlay
- When muxed /dev/i2c-0 corresponds to GPIO0/1, /dev/i2c-10 (= i2c_csi_dsi) corresponds to GPIO28/29 or GPIO44/45 (depending on the board wiring)
- When muxed /dev/i2c-11 also appears. What is the reason behind this interface?
dtOverlay=i2c0,<param> disables the muxing of the bus and assigns it to fixed pins (GPIO0/1, GPIO28/29, GPIO44/45 or GPIO 46/47) -> Becomes /dev/i2c-0
What exactly does i2c_vc=on do?
I2C1
Owned by the ARM by default
dtOverlay=i2c1,<param> can be used to assign the bus to GPIO2/3 or GPIO44/45 -> Becomes /dev/i2c-1
- What happens when GPIO44/45 is selected for I2C1 and muxing is activated for I2C0? Isn't this a conflict?
What exactly does i2c_arm=on do?
I2C3
Only available in BCM2711
dtOverlay=i2c3,<param> can be used activate I2C3 and to connect it to either GPIO2/3 or GPIO4/5 -> Becomes /dev/i2c-3
I2C4
Only available in BCM2711
dtOverlay=i2c4,<param> can be used activate I2C4 and to connect it to either GPIO6/7 or GPIO8/9 -> Becomes /dev/i2c-4
I2C5
Only available in BCM2711
dtOverlay=i2c5,<param> can be used activate I2C5 and to connect it to either GPIO10/11 or GPIO12/13 -> Becomes /dev/i2c-5
I2C6
Only available in BCM2711
dtOverlay=i2c6,<param> can be used activate I2C6 and to connect it to either GPIO0/1 or GPIO22/23 -> Becomes /dev/i2c-6
- What happens when GPIO0/1 is selected for I2C6 and muxing is activated for I2C0? Isn't this a conflict?
Thank you in advance,
Marc
I have spent the last hours trying to understanding the I2C concept on the CM4. In the follwing I will summarize my findings and my remaining questions, grouped by I2C bus. I would be happy if somebody could help answer the questions and correct me, if some findings are wrong.
I2C0
Owned by the VPU/Firmware by default
- Does this cause problems? Can the bus be used normally (if i2c_vc=on is NOT set in config.txt)?
Can be muxed between GPIO0/1, GPIO28/29 and GPIO44/45
- Muxing is activated by setting i2c_vc=on in config.txt or by enabling i2c0if and i2c0mux in a DTOverlay
- When muxed /dev/i2c-0 corresponds to GPIO0/1, /dev/i2c-10 (= i2c_csi_dsi) corresponds to GPIO28/29 or GPIO44/45 (depending on the board wiring)
- When muxed /dev/i2c-11 also appears. What is the reason behind this interface?
dtOverlay=i2c0,<param> disables the muxing of the bus and assigns it to fixed pins (GPIO0/1, GPIO28/29, GPIO44/45 or GPIO 46/47) -> Becomes /dev/i2c-0
What exactly does i2c_vc=on do?
I2C1
Owned by the ARM by default
dtOverlay=i2c1,<param> can be used to assign the bus to GPIO2/3 or GPIO44/45 -> Becomes /dev/i2c-1
- What happens when GPIO44/45 is selected for I2C1 and muxing is activated for I2C0? Isn't this a conflict?
What exactly does i2c_arm=on do?
I2C3
Only available in BCM2711
dtOverlay=i2c3,<param> can be used activate I2C3 and to connect it to either GPIO2/3 or GPIO4/5 -> Becomes /dev/i2c-3
I2C4
Only available in BCM2711
dtOverlay=i2c4,<param> can be used activate I2C4 and to connect it to either GPIO6/7 or GPIO8/9 -> Becomes /dev/i2c-4
I2C5
Only available in BCM2711
dtOverlay=i2c5,<param> can be used activate I2C5 and to connect it to either GPIO10/11 or GPIO12/13 -> Becomes /dev/i2c-5
I2C6
Only available in BCM2711
dtOverlay=i2c6,<param> can be used activate I2C6 and to connect it to either GPIO0/1 or GPIO22/23 -> Becomes /dev/i2c-6
- What happens when GPIO0/1 is selected for I2C6 and muxing is activated for I2C0? Isn't this a conflict?
Thank you in advance,
Marc
Statistics: Posted by marcp — Wed Nov 20, 2024 5:35 pm