SPI decoder
The SPI decoder I/O decodes analog data on an SPI bus to SPI data. Just measure the Clock and Data (MOSI or MISO) lines of the SPI bus with a scope and connect the measuring channels to the SPI decoder I/O.

The SPI decoder always needs two sources: the first connected source will be used as SPI clock and the second connected source will be used as SPI data, either MOSI (data output from master) or MISO (data output from slave).

When both MOSI and MISO data need to be decoded, simply use two SPI decoder I/Os, connect the CLK signal to both I/Os, the MOSI data signal to one I/O and the MISO data signal to the other I/O.

The output of the SPI decoder contains the decoded values, in hexadecimal notation, decimal notation, binary notation and in ASCII. The output can be shown in a table. When decoding both MOSI and MISO data, connect both SPI decoder I/Os to the same table, with its Layout set to "Common rows".

Properties and actions

To control the behavior of the SPI decoder I/O, several properties are available. These can be accessed through a popup menu which is shown when the I/O is right clicked.

Mode

The SPI decoder supports four SPI modes:

  • Mode 0: Clock Polarity (CPOL) = 0, Clock Phase (CPHA) = 0
  • Mode 1: Clock Polarity (CPOL) = 0, Clock Phase (CPHA) = 1
  • Mode 2: Clock Polarity (CPOL) = 1, Clock Phase (CPHA) = 0
  • Mode 3: Clock Polarity (CPOL) = 1, Clock Phase (CPHA) = 1

The Mode property determines which mode the SPI decoder uses. The default Mode setting is Mode 0.

Bit order

The bit order of transferred data on the SPI bus is not defined in a standard, it depends on the implementation. The Bit order property determines how the SPI decoder will interpret the decoded bits: MSB first or LSB first. The default Bit order is MSB first.

Word size

The word length of transferred data on the SPI bus is not defined in a standard, it depends on the implementation. The Word size property determines how many bits the SPI decoder will use for one word. Several predefined values are available and it is also possible to enter a user defined value. The default Word size is 8 bits.

Voltage

The Voltage property sets the low and high level for signal edge detection. To set the levels, enter the low level voltage and the high level voltage, separated by .. . The default levels are: 800 m .. 2.

Swap inputs

The SPI decoder always needs two sources: the first connected source will be used as SPI clock and the second connected source will be used as SPI data. When the sources are connected the wrong way, the Swap inputs action will correct it.

Common properties and actions