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Hi,
My customer is testing I2C master operation using CYUSB3KIT-003.
They used the CyU3PI2cSetConfig() API to set the I2C clock to 400khz.
But the actual frequency measured was 390khz.
Why is it slower than the setting?
How can they get the actual speed to 400khz?
Regards,
Hidekazu Omoi
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USB Superspeed Peripherals
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Hi Hidekazu-san,
The curving depends on pull-up resistor value and the bus capacitance. If the resistor value is decreased the rise time will be reduced.
The frequency drop could be due to the gpio header used. Please test the frequency isolating external connection to explorer kit by accessing the on board i2c eeprom. Verify if you are seeing 400KHz.
Regards,
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Hi Hemanth-san,
I got an I2C measurement waveform from a customer.
According to this waveform, the rise of SCL seems to be rounded.
The device they want to control is connected to the GPIO header.
Is this the cause of the frequency drop?
If correct, do they need to change the resistance to a smaller one to allow more current to flow?
Regards,
Hidekazu Omoi
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Hi Hidekazu-san,
The curving depends on pull-up resistor value and the bus capacitance. If the resistor value is decreased the rise time will be reduced.
The frequency drop could be due to the gpio header used. Please test the frequency isolating external connection to explorer kit by accessing the on board i2c eeprom. Verify if you are seeing 400KHz.
Regards,
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Hi Hemanth-san,
I understand.
They may temporarily increase the clock frequency and continue to check the operation, but they will try it later.
Thank you for your answer.
Regards,
Hidekazu Omoi