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Problem reading the SC18IS602B buffer

Question asked by Niclas Hedhman on May 10, 2019

I am using the SC18IS602B to bridge from an I2C bus to a SPI component.

 

I have gotten the "WRITE" side of the equation working. The SC18IS602B sends the data to the SPI chip as expected and I can get the SPI to return correct data when reading on the SPI device, all confirmed on the scope.

 

BUT, I can't manage to get anything but a single 0x00 byte from the SC18IS602B buffer.

 

On top of that the example in the datasheet, chapter 8, step 8 seems to be wrong, or I am missing something. It indicates 0x50 on the I2C bus after the start bit, which is a write operation. It is then very unclear about the remaining bytes whether those are coming from the microcontroller or is sent by SC18IS602B.

 

There is also remarkably little information available on the Internet and nxp.com, indicating that the chip isn't that much used.

 

So... anybody got any ideas of what I might be doing wrong?

 

FTR, in all this, I have been using "i2cdetect", "i2cget" and "i2cset" Linux commands to interact with the SC18IS602B, and maybe I need to do a write command (which the example seems to suggest, but conflicts with 7.1.4 in datasheet) and scoop up bytes coming back.

 

Datasheet I have been looking at is; https://www.nxp.com/docs/en/data-sheet/SC18IS602B.pdf 

 

Any help whatsoever is greatly appreciated.

 

Niclas

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