Tom Hill.
Tom HillI have an application that uses I2C to communicate between two MCU’s. However when I try to configure the frequency on the MDot to anything greater than 400000 Hz, it errors out indicating that I can only set between 100khz and 400khz.
1) Is this the upper limit for the frequency? Some of the other MCU’s have a fast mode for I2C, is that not available on the MDot? By the way the MDot behaves as the I2C slave.
2) Should I be even setting the frequency when it is the I2C Slave?
3) If not, if the other MCU is able to operate at a higher frequency, would the I2C slave be able to work at this higher frequency.
Btw I am using the LibMdot dev built and MBED OS 5.2.3.
Thanks,
Yogesh
Leon LindenfelserHi Yogesh,
In both the data sheet and the reference guide for the mDot processor, it states that the I2C interface supports the standard (up to 100 kHz) and fast (up to 400 kHz) modes. Both documents also say that the I2C bus frequency can be increased up to 1 MHz but to contact a ST sales rep for details.
The I2C master provides the clock but there is some internal clock configuration that occurs under the hood on slave devices. So it might be necessary even though it does not generate the clock. Configuring the clock in slave mode shouldn’t hurt anything.
Kind regards,
Leon
Tom HillThanks Leon for your input. I am a little confused, why would I need to reach out to ST’s sales rep? Shouldn’t I be working with Multitech’s sales rep? Since we purchased the MDot product from Multitech?
Thanks,
Yogesh
Leon LindenfelserHi Yogesh,
Sorry, I was providing you with information straight from the ST Micro datasheet. I have not explored running the I2C interface faster than 400kHz. Here is a link to the datasheet for the processor we use on the mDot. Please see section 3.21.
http://www.st.com/content/ccc/resource/technical/document/datasheet/b3/a5/46/3b/b4/e5/4c/85/DM00115249.pdf/files/DM00115249.pdf/jcr:content/translations/en.DM00115249.pdf
If speeds greater than 400kHz are critical to your application, I can reach out to ST Micro to see what is required to exceed 400kHz.
Kind regards,
Leon
Tom HillHi Leon,
Sorry I got a bit side tracked and was facing issues with I2C even at 400khz. However it is working now. For now we should be able to make do with 400khz speed. However my client was looking to gather all the information incase we need to use 1mhz speed, so when designing our final board we will have no surprises.
Thanks,
Yogesh