i2c_sam0 LOWTOUT is not functional #21232
Assignees
Labels
Comments
carlescufi
added
priority: low
sslupsky
added a commit
to sslupsky/zephyr
that referenced
this issue
Jul 10, 2020
Optimizations: When using system power management, the bus transactions can be interrupted by low power modes which causes excessive power consumption and can cause the transactions to terminate before completed. Further, other interrupts can cause bus transaction anomalies. When using the RESTART flag, the MB and SB bits must be cleared. This commit prevents interruption of the bus during low power modes and correctly clears the MB or SB flags when a bus transaction is restarted. Also fixes an initialization problem with the INACTOUT timer and ensures the LOWTOUT is properly configured when using i2c_configure(). The GCLK_SERCOM_SLOW clock is used to time the i2c time-outs and must be configured to use a 32KHz oscillator. See 28.6.3.1 This commit configures GCLK4 to 32768 Hz Fixes zephyrproject-rtos#21711, zephyrproject-rtos#21549, zephyrproject-rtos#21233, zephyrproject-rtos#21232, zephyrproject-rtos#21114, zephyrproject-rtos#21092 A problem can arise when back to back transactions occur before the STOP transaction is complete. This commit also introduces a busy wait for the STOP to complete with an timeout in the event there is a bus failure. Signed-off-by: Steven Slupsky <[email protected]>
|
This issue has been marked as stale because it has been open (more than) 60 days with no activity. Remove the stale label or add a comment saying that you would like to have the label removed otherwise this issue will automatically be closed in 14 days. Note, that you can always re-open a closed issue at any time. |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Describe the bug
When using the i2c_sam0 driver, SCL remains low indefinitely after a bus transaction. SCL should be released when a bus transaction completes. LOWTOUT is intended to guard against situations where SCL is held low too long.
The i2c_sam0 driver enables LOWTOUT (SCL low timeout). However, the driver does not initialize GCLK_SERCOM_SLOW which is required to enable the timeout (see 28.5.3 and 28.6.3.1).
To Reproduce
Steps to reproduce the behavior:
Expected behavior
SCL will be released after the LOWTOUT timeout.
I applied the following patch to i2c_sam0_initialize() to test the expected behaviour:
Impact
When SCL is held low, the pull up resistors on the bus consume power on the order of 500uA or more (depending on the value of the pull up resistor). This bug rules out any low power applications that require the i2c driver.
The text was updated successfully, but these errors were encountered: