imx6ul spi communication with buffer IC

[surendradhobale]

Hello,

      We are using the imx6ul based custom board. We are require multiple Serial Port (RS485), so used MAX14830 expansion chip to achive the ports on the SPI.

To get good signal strength we have added one buffer IC in betwen the CPU board and SPI-UART expander ( MAX14830).

But currently problem is, the communicaion is working very fine without the buffer.( as shown in below 2nd diagram)

but not reliable communication with 1st diagram setup.

We are looking to use the buffer in our setup.

What kind of the timing related changes required for same on SPI or Max14830 driver?

We are using 4.1.15 or 4.9 kernel (both having same behaviour).

Kindly help , if we are looking to add the buffer IC, what kind of changes required either in software side (i.e in linux kernel).

Regards,

Surendra

[igorpadykov]

Hi Surendra

one can check with oscilloscope ecspi timings and compare with good setup,

in particular CS8 -  ECSPIx_MISO Setup Time, described in

Table 47. ECSPI Master Mode Timing Parameters i.MX6UL Datasheet
http://www.nxp.com/docs/en/data-sheet/IMX6ULCEC.pdf

these timings are hardware timings and can not be changed by software.

Best regards
igor
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