No MISO activity needed during MOSI operation in iMX8MM EVK

[sreedhar_appala]

Hi,

I am working with iMX8MM EVK and Yocto distribution 4.19.35 version

Build Configuration:
BB_VERSION = "1.42.0"
BUILD_SYS = "x86_64-linux"
NATIVELSBSTRING = "ubuntu-16.04"
TARGET_SYS = "aarch64-poky-linux"
MACHINE = "imx8mmevk"
DISTRO = "fsl-imx-xwayland"
DISTRO_VERSION = "4.19-warrior"
TUNE_FEATURES = "aarch64"
TARGET_FPU = ""

We have interfaced an SPI slave to ecspi2 on J1003 of i.Mx8MM EVK.

ECSPI2 as master, When i do the SPI write operation.

I am observing same data on the MISO line of MOSI line.

Actually as per the data format of the slave, only during the read operation MISO sends the data to Master.

I would like to make MISO line to be sending nothing during spi write.

I checked the ECSPI2_CONFIG and ECSPI2_CONTROL register. I could not find to cutoff MISO activity during spi writes.

Please let me know is there any register bit to achieve what i need.

Thank you, Sreedhar

[#2]

Hi,

I am working with iMX8MM EVK and Yocto distribution 4.19.35 version

Build Configuration:
BB_VERSION = "1.42.0"
BUILD_SYS = "x86_64-linux"
NATIVELSBSTRING = "ubuntu-16.04"
TARGET_SYS = "aarch64-poky-linux"
MACHINE = "imx8mmevk"
DISTRO = "fsl-imx-xwayland"
DISTRO_VERSION = "4.19-warrior"
TUNE_FEATURES = "aarch64"
TARGET_FPU = ""

We have interfaced an SPI slave to ecspi2 on J1003 of i.Mx8MM EVK.

ECSPI2 as master, When i do the SPI write operation.

I am observing same data on the MISO line of MOSI line.

Actually as per the data format of the slave, only during the read operation MISO sends the data to Master.

I would like to make MISO line to be sending nothing during spi write.

I checked the ECSPI2_CONFIG and ECSPI2_CONTROL register. I could not find to cutoff MISO activity during spi writes.

Please let me know is there any register bit to achieve what i need.

Thank you, Sreedhar

[igorpadykov · Accepted solution]

Hi sreedhar_appala

when i.MX8MM eCSPI is master, MISO signal is an input and only slave signal can drive it

as described in sect.10.1.2.4.1 Typical Master Mode i.MX 8M Mini Applications Processor Reference Manual

"When the ECSPI is in Master mode the SS, SCLK, and MOSI are output signals, and the
MISO signal is an input."

Best regards
igor

[sreedhar_appala]

Thank you igor !!