• Buffer last command in serial.c
• Add single character shortcuts for commands in serial.c
• Add a toggle command for GP1
• Add configurable duty_frac (not sure if that makes sense, does less duty_frac mean less voltage mean weaker pulse?), configurable pulse_time

Hey It seems that either J2 or BH1 are the wrong part number here. I ordered according to BOM (S2B-XH-A(LF)(SN) and PRT-09925). They do match, but the polarity is reversed. The VCC on battery holder matches the GND on the pin header/PCB. The one shown in your Youtube video has the right polarity though.

Please see the attached pictures:

Here's yours. Please note the difference:

Hey Colin I built a PicoEMP today, however I was not sure how to properly test it to make sure everything is working as expected. I uploaded the C-based firmware, and initially everything seemed to be working (LEDs working. Pushing ARM made D6 turn on, etc) After a few times pushing the ARM and PULSE buttons, device stopped working (LEDs stayed ON. I reset the device and now LEDs don't turn on. The rpi pico's builtin LED dimly turns on and then off. I think maybe rpi is damaged. Is it possible to actually somehow damage the rpi pico?) Now if I turn it on and wait a few minutes, the ARMING LED dimly turns on and if I push (and hold) the ARM switch, the LED also gets brighter. Did you face any similar issues while building your samples? Visually everything seems to be ok. Not sure where to start with spotting the faulty part.

I was using this isolator - https://www.aliexpress.com/item/4000047053305.html (mentioned in https://github.com/newaetech/chipshouter-picoemp/issues/2#issuecomment-999962799) as intermediate between computer and target (Atmega328), PicoEMP on completely separate power source (since I needed to see USB-serial output to see if glitch was success).

Somehow during the session I managed to shock USB bus through Atmega target connected via the isolator on both computer and monitor USB hubs so they disconnected (power cycling did fix it, so nothing permanent thank god). I am pretty sure I did not short anything, but even in that case the isolator is rated according to docs to 1.5 kV. So this shoudln't have happened, but the quality of the isolator is also question.

There was a powered hub behind the the USB isolator (Atmega<->USB isolator<->powered USB hub<->computer+monitor), but I seriously have no idea which part of the setup could have caused this. Hundreds of glitch attempts were fine until this one.

Even if this was some stupid mistake, there was definitely no direct contact between any parts after the USB isolator.

When trying to order the board from Aisler, a warning is shown, saying that the Gerber files don't have some required information on the inner milling paths meant for the shield. As the repository doesn't contain any EDA project files, I can't really fix it myself.

(This is the "Design Guidelines" link from the screenshot.)

(Also, would it be possible to have a PCB that conforms to Aisler's "simple" design rules? This would reduce the cost of ordering one.)

First of all, thanks for open sourcing the design! Very excited to try it out.

Q3 and Q4 where missing from the table. This PR adds AO3422 as from the xls BOM.

The suggest sub part (PMV37ENEAR) is now also out of stock on digikey/farnell. Any suggestions for a different sub?

I also made a list with Farnell part numbers (https://docs.google.com/spreadsheets/d/1lR9KH1mVs3pNZHqpcGG9F5pi7PmbyUwxurxPG0W1xi4/edit?usp=sharing). Feel free to use that list for whatever you want.

Summary of changes:

• Add a configurable delay to the PIO trigger program (i.e. fast_trigger). This (and the pulse duration) are counted in 125MHz cycles.
• Use side for controlling outputs instead of set instruction.

One downside with fast_trigger is that there is currently not any kind of timeout implemented, so if the input trigger never comes, the serial interface hangs there forever.

Another maybe downside in general is that serial interface is becoming a bit convoluted with all the options and inputs. For example, now there are two configurable pulse_times, one that goes into a sleep_us and one that goes into the PIO program.

There is a paper by Toulemont, J., et al. on "A Simple Protocol to Compare EMFI Platforms." which suggests that the ringing/reflection at the coil immediately after a high voltage pulse is a problem and that it can be limited through the use of an inexpensive diode (2020, IACR preprint).

They propose adding an unidirectional Littlefuse 1.5KE600A transient voltage suppressor (TVS) diode between the voltage generation output and the probe tip to clamp some of the voltage swings.

Based on the tests shown in the introduction video, there are not a lot of oscillation cycles for the tested coil on the picoemp, so the main benefit I can see is to reduce the second half-wave of the pulse and maybe reduce the first oscillation after that. However, I'm not sure in if this would result in noticeable benefits during picoemp usage since timing considerations are probably not as important for picoemp users and the second full cycle may not actually inject much voltage into the target. So the improvement could be to suppress the reverse injection effects of the second half-wave on the target and make the picoemp slightly more targeted/precise? I'm not certain I've gotten the physics right here, so this is very speculative.

The ca. 250V maximum capacitor voltage of the picoemp looks compatible with the min. 570V breakdown voltage safety rating of the mentioned diode, the diode is currently available & low cost, which are some of the reasons I'm considering this. The diode could be located on a small SMA-based filter (as used in the paper) or built directly into custom probe tips (incompatible with higher-voltage glitchers).

@colinoflynn You're likely aware of this protection diode concept, what are your thoughts on this? Is it relevant within the typical picoemp pulse behavior and parameters? Thanks!

Preface: I'm not an expert at high voltage electronics. Do not rely on any of the assumptions in this post. Do any modifications at your own risk.

Based on my understanding of the picoemp design, capacitor C3 stores about (0,47µF * (250V)^2)/2 = 14,69mJ of energy assuming a charge voltage of 250V, a part of which can be used for a discharge into the coil. In the introduction video, the measured charge voltage is about 239V and I've measured about 258V on my own unit, so 250V looks reasonable as a ballpark figure.

"Bigger" designs like the regular chipShouter, siliconToaster etc. allow higher capacitor voltages in the area of 500V-1200V at their highest settings which significantly benefits the energy storage through the quadratic component. It would probably be possible to tweak the picoemp to work at a higher voltage than 250V (for example 300-400V), but I'm very cautious about such a modification since this reduces the safety margin for breakdown voltages (IGBT, capacitor, ..) and physical board or probe tip clearances. It would be very unfortunate if boards have a catastrophic breakdown due to left-over solder paste, partially exposed traces, ringing with mismatched experimental probe tips or one of the many other failure modes for self-assembled boards.

So I have been wondering about the benefits or drawbacks of increasing just the size the capacitor "bank" at C3 by factor two to four. The standard picoemp design is clearly limited by the BOM cost and area/height under the plastic shield, so it is logical to me that "only" a single capacitor was chosen. (Also note that the Hammond 1551 enclosure has an additional plastic part in that corner of the board which needs to be stripped before that space is usable for high components).

@colinoflynn Are you aware of any direct electrical drawbacks to doubling C3 by stacking an identical 2.5mm height capacitor on top (which could just fit the enclosure) for people who have used the thinner TDK CGA9P1X7T2J474K250KE per your BOM recommendations since Murata KRM55TR72J474MH01K wasn't available? Alternatively, there appear to be a few capacitor candidates with nominal 1µF which are thin enough to fit under the shield (untested candidates: Kyocera AVX 2220CC105KAZ2A, Knowles Syfer 2220Y6300105KXTWS2 and its more expensive AEC-Q200 twin). Based on the datasheets, 1 to 1.2µF is the upper end of capacitors in this package size at 630V, so there may be capacitor design limitation drawbacks that I'm not aware of which motivate staying at the slightly more conservative 0.47µF choice. With a custom 3D-printed shield and larger inner shield height, it looks possible to stack some more capacitors on C3 and go for the mentioned 4x capacitor increase.

Looking at the PCB layout, it may be possible to rotate the C3 component counter-clockwise and squeeze another 2220 footprint into the layout for optional used by people who want the additional BOM cost for higher capacity trade-off. It's probably going to be fairly close to the plastic shield mounting clearance, though. (Related idea: it looks like R2 and J3 could be swapped and J3 turned counter-clockwise to simplify the trace routing and increase distances. However, this takes more space along the shield and therefore works against adding another capacitor footprint).

From what I can tell, the recharge rate of the capacitor bank will not change with a size increase, so I expect the main effect to be a larger initial energy supply.

The BOM identifies D2 as a 600V, 2A fast recovery diode. The part # in the BOM and the alternate are both 1A. C1 and C2 GRM32ER71H475KA88L refers to a 1210 package cap, not an 0805

• The fast_trigger mode could only be used 4 times, attempting to use it a fifth time would result in the Pico panicking. 'fixed' by only calling pio_add_program the first time.
• Added an external HVP mode that configures the Pico HVP GPIO pin as an output. Can be used to control the HVP signal from a ChipWhisperer or other pulse generator.
• Added an injection tip example based on the WE 744779068 inductor.

hi, I would like to know if it would work with old TV Flyback. Yoke part has 1000v for 15750hz. could use a FET IGBT switch to turn it on for x time.

thanks, Carlos.

Hello

I have some issues with building this nice device.all parts were used from the bom list except RGT16BM65DT i used instead IKD06N60RATMA1.

Gerber files used were rev04_normal.zip also with milled slots for the protection shield. >> i ordered the boards from JLCPCB

The solder orientation for the LEDs wasnt so clear to me,so i modified the micropython firmware to run a LED check on startup which works great.

So the actual problem :

The test header (J3) shows only 7V when the ARM button is pressed but the HV LED wont turn on so Pulse doesnt work either.Voltage on (P3) is approx 3V which seems to be correct.Discharge button works.

I looked at the firmware and changed the PWM duty which seems also to work i gained then 12V but its still alot missing hehe

Somewhere i did an error i think but i also rechecked already the solder orientation for the different smd parts. So can anyone please point me in the right direction and give me some hint?

Should i maybe test the C Firmware? But there is also still some issue with the arming button ive read. >> so i compiled the C Firmware and that isnt the Problem.The Arm Button still has issue.

Thanks

Greetings

Added in the main a brief power ON and OFF for all LEDs, so at startup we can chek if LEDs are working correctly. LEDs in this board are very small and it is very easy to invert polarity. Also checking HV led functionality is very important. Removed from picoemp.c the status led and moved to main when the initialization is really complete.

Hello

From the schematics and the code it seems HVPULSE is constantly driven by the RP gpio so it seems a bit dangerous to overwrite the signal with an external trigger source without disconnecting first the RP. Would it make sense to modify the RP firmware such that:

• picoemp_configure_pulse_output configure it with a pull-down, idle state is HiZ + pull-down
• picoemp_pulse set to high then back to HiZ

So we could overwrite HVPULSE with an external source without worry.