Important changes to forums and questions
All forums and questions are now archived. To start a new conversation or read the latest updates go to forums.mbed.com.
9 years, 4 months ago.
FRDM KL46Z I2C clock pin blocked
Dear all, I'm in great need for help. I'm running a FRDM KL46Z and a custom developed board that connects the mbed to an I2C LCD driven by a PCF8574 IC.
I'm using I2C1 driver pins PTC1 and PTC2. My code tries to write every second to the slave and reads the result of write operation. Still I was not able to do the connection between mbed I2C driver and PCF8574 IC .
I checked the i2c bus transmission and I can see on the scope that the SCL of the I2C is continuously transmitting (see attached picture).
I have unhooked the custom board on which there are also the pull up resistors and the clock signal is still available on PTC1 pin. It looks to me like a internal clock. Please let me know how can I solve this issue. Thanks, Mircea.
1 Answer
9 years, 4 months ago.
The kl46 uses the SCL pin for the 32kHz RTC. The signal is generated by the SDA interface and provided to the target processor on the SCL pin. This should be better documented. Check the schematic on the platform page. You should either use a different I2C pin or modify the board and remove a resistor. That modification means you loose the RTC.