I am using an ATTiny88 MCU as master over an Si4012 slave. The MCU is running code produced by Arduino IDE. Connecting a logic analyzer to the SCL and SDA lines produce an output as below - second scren grab. This logic analyzer may not be the best: if I try connecting its CLK input to SCL line then the I2C interface stops working ( and I do not know where else to get a clock signal for the analyzer from). Thus the analyzer is running its own internal clock while sampling @ 16 MHz. However, I can't see why there is this 1.953 kHz SCL reading coming from. Tried with both 100 and 400 kHz SCL rates - the analyzer shows the same 1.953 kHz clock rate... How come ? Any quick other way to establish the real I2C frequency without a scope ?
#define F_TWI 400000L //#define F_TWI 100000L .... Wire.begin(); // Initiate the Wire library Wire.setClock(F_TWI);
As per Olin's comment - new image. Forgot to mention the two pullups are 3k3 and the rail is 3v3. Also I should note that the clocks of I2C and logic analyzer go out of sync quite fast as it can be seen in the first screen grab of the first image. Oh, and the MCU is running on its internal oscillator at 1 MHz.