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diff --git a/docs/i2c-debugging.md b/docs/i2c-debugging.md new file mode 100644 index 0000000000..a1a56db285 --- /dev/null +++ b/docs/i2c-debugging.md @@ -0,0 +1,48 @@ +I²C Debugging Tips +================== + +The EC codebase has functionality to help you debug I²C errors without +pulling out the scope. Some of the debug functionality is disabled by +default to save space, but can be enabled with the `CONFIG_I2C_DEBUG` +option. + +Tracing +------- + +You can use the `i2ctrace` command to monitor (ranges of) addresses: + + i2ctrace [list + | disable <id> + | enable <port> <address> + | enable <port> <address-low> <address-high>] + +For example: + + > i2ctrace enable 0 0x10 0x30 + > i2ctrace enable 0 0x40 0x50 + > i2ctrace list + id port address + -- ---- ------- + 0 0 0x10 to 0x30 + 1 0 0x40 to 0x50 + ... debug spam may follow ... + i2c: write 0:0x50 A8 + i2c: read 0:0x50 00 02 00 06 00 44 + ... + > i2ctrace disable 1 + > i2ctrace list + id port address + -- ---- ------- + 0 0 0x10 to 0x30 + +A maximum of 8 debug entries are supported at a single time. + +Note that `i2ctrace enable` will merge debug entries when possible: + + > i2ctrace enable 0 0x10 0x30 + > i2ctrace enable 0 0x40 0x50 + > i2ctrace enable 0 0x31 0x3f + > i2ctrace list + id port address + -- ---- ------- + 0 0 0x10 to 0x50 |