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PSoC 5, 3 & 1 MCU

New Contributor

Hi,

I found out during troubleshooting that the SDAT pin of Serial Peripheral Interface Master does not change state during transmission.

The SPI is set as bi-directional.

The clock and the  slave select pins work as intended.

Configuring the SPI Master a MOSI+MISO does output data.

What is wrong with the SDAT pin ? None of the examples I found seem to use a working solution of a SPI Master bi-directional.

Additional settings:

DEV KIT : PSOC 5LP (CYC85888LTQ-LP97 )

Mode CPHA=1, CPOL=0 : sellected to operate as SSC protocol

Data Lines: Bidirectional

SDAT pin:

Bidirectional

External terminal

Initial drive state: low

Drive mode: open drain drives high. ( I tried several combinations with pull up resistor etc no change)

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1 Solution
Honored Contributor

Hi acawhiz,

You indicated "Drive mode: open drain drives high. ( I tried several combinations with pull up resistor etc no change)".

Here's a note for the pin datasheet:

Drive Mode

This parameter configures the pin to provide one of the eight available pin drive modes. The

defaults and legal choices are influenced from the Type selections. Refer to the device

datasheet for more details on each drive mode. A diagram shows the circuit representation for

each drive mode as it is selected.

▪ If the Type is Digital Input or Digital Input/Analog, the default is High Impedance Digital.

▪ If the Type is Analog, the default is High Impedance Analog. This is the only pin drive

mode that can support purely Analog pins.

▪ If the Type is Bidirectional or Bidirectional/Analog, the default is Open Drain, Drives Low.

▪ All other pin types default to Strong Drive.

Hope this helps.

Len
"Engineering is an Art. The Art of Compromise."

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1 Reply
Honored Contributor

Hi acawhiz,

You indicated "Drive mode: open drain drives high. ( I tried several combinations with pull up resistor etc no change)".

Here's a note for the pin datasheet:

Drive Mode

This parameter configures the pin to provide one of the eight available pin drive modes. The

defaults and legal choices are influenced from the Type selections. Refer to the device

datasheet for more details on each drive mode. A diagram shows the circuit representation for

each drive mode as it is selected.

▪ If the Type is Digital Input or Digital Input/Analog, the default is High Impedance Digital.

▪ If the Type is Analog, the default is High Impedance Analog. This is the only pin drive

mode that can support purely Analog pins.

▪ If the Type is Bidirectional or Bidirectional/Analog, the default is Open Drain, Drives Low.

▪ All other pin types default to Strong Drive.

Hope this helps.

Len
"Engineering is an Art. The Art of Compromise."

View solution in original post

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