Logic Analysis

Let’s take a look at how we can use GreatFET One as a logic analyzer for 3.3 V digital signals. (For I/O voltages other than 3.3 V, you would also need a level shifter.)

The GreatFET logic analysis function uses a peripheral called SGPIO, so we need to connect the SGPIO pins to our target signals. One easy way to find a target is to use one of the GreatFET’s other peripherals such as SPI.

Use jumper wires to make the following connections:

• Connect J1 pin 4 (SGPIO0) to J1 pin 37 (CS)
• Connect J1 pin 6 (SGPIO1) to J1 pin 38 (SCK)
• Connect J1 pin 28 (SGPIO2) to J1 pin 39 (COPI)
• Connect J1 pin 30 (SGPIO3) to J1 pin 40 (CIPO)

Open an interactive Python shell in your first terminal window:

gf shell

FIXME set up SPI

In a second terminal window activate logic analysis:

gf logic -p /tmp/spi-capture

FIXME file extension?

In the Python shell, type:

gf.spi.transmit(b"GreatFET")

In the second window, terminate gf logic by typing ctrl-c.

FIXME open in pulseview

FIXME analyze in pulseview