Dragonzap

Introduction

Dragonzap is a PCB for voltage glitching. It provides both a SPDT switch for quickly switching between a high and a low voltage (controlled by a DAC), and a MOSFET circuit for crowbar glitching. GPIOs to interact with the DUT can go through a level shifter.

The PCB is about 9.2 cm by 5.4 cm in size.

Images

Front

Back

3D view, with components

Notes

External module and footprint sources:

• https://github.com/ncarandini/KiCad-RP-Pico (Pico)
• https://github.com/lethalbit/aki-eda (Samtec FTSH SWD debug connector)
• https://git.lain.faith/sys64738/pcbs/src/branch/main/chip-bo (4x2 jumper, Xenia silkscreen image)

Usage

Firmware of the Pico controller is still TODO. Most of the documentation can be found on the PCB silkscreen.

Pico pinout

Name	Pico pin	Usage
DUT GPIO	GP0..GP7	Generic GPIO to the target DUT, goes through level shifter U200 and out to J200. GP0 and GP1 are also connected to JP100 for UART.
RV50x	ADC0, ADC1	Potentiometers that can be used for manual parameter tweaking.
DACVCC/2	ADC2	Can be used to calculate the maximum voltage the DAC can reach, for calibration.
TRIG IN	GP10	DUT trigger input.
GLITCH SIG	GP11	DUT glitch (voltage supply) output, from U400.
CB1 (Q300)	GP12	Crowbar gate 1
CB2 (Q301)	GP13	Crowbar gate 2
DAC nLATCH	GP17	nLATCH signal of the DAC (U401).
DAC CLK	GP18	SPI clock signal of U401.
DAC TX	GP19	SPI controller-to-device data signal of U401.

BOM

Base components

Ref	Quantity	Product	Footprint	Description	Notes
U100	1	Raspberry Pico	Pico module	Raspberry Pico module/board	This one serves as the glitch controller. Very important.
C100	1	47 uF	THT Radial P2.00mm	Electrolytic capacitor	Extra decoupling capacitor for the Pico.
J200	1	Pin header 01x08	THT 2.54mm 01x08	Generic pin header	Main GPIO to DUT connector, goes through level shifter U200.
J201, J202, J205	3	Pin header 01x01	THT 2.54mm 01x01	Generic pin header	Main glitching to DUT connectors (pin headers).
J203, J204, J206	3	Amphenol 132289	SMA edge-mount connector	SMA connector	Main glitching to DUT connectors (SMA connectors). Has many other compatible connectors.

Optional connectors

Ref	Quantity	Product	Footprint	Description	Notes
J207	1	Pin header 02x05	THT 2.54mm 02x05	Generic pin header	Power out (and extra external voltage in) connector.
D100	1	1N4001	SOD-123	Generic or Schottky diode.	Reset diode for external reset signal (SWD).
J100	1	Pin header 01x04	THT 2.54mm 01x04	Generic pin header	UART connector (nonstandard, 2.54mm jumper)
J101	1	Pin header 01x05	THT 2.54mm 01x05	Generic pin header	SWD connector (nonstandard, 2.54mm jumper)
J102	1	FTSH-105-01-L-DV-007-K	THT 1.27mm 02x05 -OR- FTSH-105 SMD	Cortex debug connector	SWD connector (standard FTSH connector, 1.27mm pitch, either through-hole or surface-mount)

Manual control potentiometers

Ref	Quantity	Product	Footprint	Description	Notes
RV500, RV501	2	Potentiometer	THT 2.54mm 1x3	Potentiometer with colinear leads.	Used for optional manual control of parameters.

If you need the "emergency reset button"

Ref	Quantity	Product	Footprint	Description	Notes
Q1	1	Generic NMOS	SOT-23 (GSD)	N-MOSFET transistor	Make sure it is completely on at a Vgs of 3.3V! Invertor NMOS for reset signal.
SW1	1	Push button	THT 4-lead 6x6mm	Two-by-two push button switch, generic	Make sure the bends in the pushbutton leads are parallell with the lines on the silkscreen.
R1, R2	2	220k	0805	Resistor	Pullup/pulldown resistors.

The emergency reset button will stop U100, and disable most other ICs (eg. U400, U200).

If you need the DAC

The DAC can be used for the level shifter, crowbar glitcher and SPDT glitcher (selected using JP200, JP300 and JP500).

Ref	Quantity	Product	Footprint	Description	Notes
U401	1	MCP4802	SOIC-8 3.9x4.9 (U401a) -OR- MSOP-8 3x3mm P0.65mm (U401b)	2-channel 8-bit DAC, SPI interface.	DAC, optional. If not placed, you probably want to short JP500, and short the two leads as indicated on the silkscreen. SOIC and MSOP both work. MCP4812 or MCP4822 can be used, too.
R500, R501	2	220k	0805	Generic resistor	Voltage divider for max voltage sensing of U401. Only needed if you place the DAC (U401).
C401	1	10 nF	0805	Unpolarized (MLCC) capacitor	Decoupling capacitor for U401. Optional.

If you need the level shifter

Ref	Quantity	Product	Footprint	Description	Notes
U200	1	TXS0108EPW -OR- NXS0108PW	TSSOP-20 4.4x6.5mm P0.65mm	Bidirectional level-shifting voltage translator	The level shifter. Source from TI or Nexperia.
R200	1	47k	0805	Pulldown resistor	Used for the enable line of U200.
JP200	1	Pin header 02x04	THT 2.54mm 02x04	Level shifter external voltage selector.	Place a generic pin header here, use a pin shunt to select the voltage.

If not using the level shifter, short the leads of the footprint of U200 as shown on the PCB silkscreen.

If you need the crowbar glitching circuit

Ref	Quantity	Product	Footprint	Description	Notes
Q300	1	IRF7807/Si4850BDY/Si3463BDY	SOIC-8 3.9x4.9mm	N-channel Power MOSFET, SO-8	Slower but higher-duty (current-wise) crowbar MOSFET. Need not be placed if Q301 is present.
Q301	1	IRLML2502/IRLML6204	SOT-23	N-channel MOSFET, SOT-23	Faster but more fragile crowbar MOSFET. Need not be placed if Q300 is present.
R300	1	50 Ohm	0805/1206/2010/2512	Current limiting resistor	Current limit resistor through which power is optionally supplied to the target. Several footprints work. Use eg. ESR10EZPF49R9.
JP300	1	Pin header 02x04	THT 2.43mm 02x04	Generic pin header	Crowbar power supply, place generic pin header and use a pin shunt. Can be left open if target is self-powered.

Note, Q300 and Q301 are selected by separate GPIO lines on the Pico.

If you need the SPDT switch glitching circuit

Ref	Quantity	Product	Footprint	Description	Notes
U400	1	MAX4619CSE+	SOIC-8 3.9x4.9mm	Triple analog SPDT switch	Fast SPDT switch IC, used for glitching (selecting between high and low voltage levels).
R400, R401	2	220k	0805	Generic resistor	Pullup/pulldown resistors for the enable line of U400.
C400	1	10 nF	0805	Unpolarized (MLCC) capacitor	Decoupling capacitor for U400. Optional.