EVALSTPM34 SPI Interface and SYN line

Rob Parsons · ‎2017-05-05

Posted on May 05, 2017 at 18:05

I am trying to connect the EVALSTPM34 SPI interface to a microprocessor board that has a PMOD interface (see attachment) that is configured to support SPI.

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PMOD SPI Interface to EVALSTPM34 Metering Board

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Set rotary switch to 2

MASTER SLAVE

(freja board) (EVALSTPM34 board)

PMOD J6 'SPI'

1 (SS) ------------> (SCS) 5

2 (MOSI) ---------> (MOSI) 2

3 (MISO) <---------- (MISO) 4

4 (SCK) -----------> (SCL) 6

(GND) 3

(VCC) 10

(SYN) 8

(NC) 1

(NC) 7

(NC) 9

I am only using 4 lines of the SPI interface.

The SYN line is not connected.

Section 8.6.1 of the attached DM00111861 datasheet describes how the SPI SYN line is used for latching and resetting.

I am using this method to latch register values: 'Writing the channel latch bits before each reading (S/W Latchx in DSP_CR3)'

It is not clear how the SYN line is used for normal read/write transactions.

Is is required to use the SYN line for normal read/write transactions?

#evalstpm34

Rob Parsons · ‎2017-05-26

Posted on May 26, 2017 at 19:04

Answer is...

SYN line is not required for normal read/write transactions.

We finally got the SPI interface working between the PMOD SPI interface and the EVALSTPM34 SPI interface.

How?

You have to have common ground between external boards.

After connecting pin 5 (GND) on the PMOD SPI interface to pin 3 (GND) on the EVALSTPM34 SPI interface, the clock signals cleaned up and the read/write transactions started to be successful.