PI Pico Pulse Generator

This tool is using a Raspberry Pi Pico as a configurable pulse and delay generator. It was designed for usage in fault injection, specifically for usage with the ChipShouter.

A rising edge on the trigger input will initiate a pulse of at a configurable offset to the trigger signal. The length of the pulse can be configured and optionally it can be repeated a specified number of times with a specified spacing.

The PIO blocks of the pico are used to achieve consistent timing. The output trigger duration can be configured over serial with a resolution of 5 ns (1 clock cycle of the Pi Pico at 200 MHz). Currently a 256 cycle (1280 ns) cooldown is implemented (hardcoded in pio) to prevent retriggering by the jitter from an EM glitch. The rise and fall time for the GPIOs is about 2.5 ns each (measured with 10x oscilloscope probe, otherwise unloaded).

• offset:
  • min = 10 ns (2 cycles)
  • max = 21.47 s (4294967295 cycles)
  • measured offset is always 1.6 ns larger that specified (meauring trigger and first rising edge at 2V threshhold)
• length:
  • min = 5 ns (1 cycle)
  • max = 635 ns (127 cycles)
• spacing:
  • min = 30 ns (6 cycles)
  • max = 5.24 ms (1048575 cycles)
• repeats:
  • min = 0
  • max = 31

Wiring

• trigger input -> GPIO_0
• pulse output -> GPIO_1

Build Instructions

export PICO_SDK_PATH=/opt/pico-sdk
mkdir build
cd build
cmake ..
make

Usage

The output trigger duration can be controlled in clock cycles of the pi pico (5 ns each). By default the output trigger duration is set to 10 clock cycles (= 80 ns). It will automatically convert ns into clock cylces and throw an error if conversion is not possible.

The delay_control.py script can be used to set or get the parameters over serial.

In bash commandline:

python3 test.py --port /dev/ttyACM0 --get offset

python3 main.py --set offset=150
python3 main.py --set offset=150 length=50 repeats=2 spacing=300

In python (see test_delay_control.py):

from delay_control import DelayController

try:
    with DelayController() as dc:
        # Set parameters
        dc.set_parameters({"offset": 150, "length": 50, "repeats": 2, "spacing": 300})

        # Get parameters
        offset = dc.get_parameter("offset")
        length = dc.get_parameter("length")
        repeats = dc.get_parameter("repeats")
        spacing = dc.get_parameter("spacing")

except serial.SerialException as e:
    print(f"Serial error: {e}")
except ValueError as e:
    print(f"Communication error: {e}")

Example Measurements

• offset: 15
• length: 20
• spacing: 15
• repeats: 2

• offset: 2
• length: 1
• spacing: 6
• repeats: 3

Future Improvements

• Allow configuration of input and ouput as active low / active high
• Allow configuration of cooldown in pulsegen.pio (prevents retriggering due to jitter of trigger input)