Hacking Hardware Picofly - a HWFLY switch modchip

[Relon]

I had this problem yesterday. I put a 10k resistor as a Chinese video a saw and it works fine.

It should be 4k7 To measure it you must first remove it from the board.

 

[CodyRoseman]

Post automatically merged: May 30, 2023

I like the Idea that put the CPU point at the Right.
I think I will try it at next Revision.

Yeah, the point comes out just next to the ram, makes it ideal to run an insulated wire through the opening in the metal enclosure. Just makes sure if you use enamel wire not to let it expose the wire on the sharp edges of the enclosure from movement, I use a thin silicon insulated wire from Adafruit.

 

[rsilveira1991]

It should be 4k7 To measure it you must first remove it from the board.

Yeah. I see now that 4k7 is the right value. but with 10k works fine. let hope continue that way.

 

[CodyRoseman]

Here is a rp2040 + dual mosfet board, it's untested at the moment, I'll get back to to the thread once my boards have arrived.

It measures about 14mmx 25mm from memory. If you order the board with 0.8mm fr4(economical) the total height is around 1.7mm, otherwise with 0.1mm flexible polymide the total is about 1mm.

https://drive.google.com/drive/folders/1lldumDr7aOpNCwfE2Vw_DBWkPrt6qRWx?usp=drive_link

 

[lightninjay]

Here is a rp2040 + dual mosfet board, it's untested at the moment, I'll get back to to the thread once my boards have arrived.

It measures about 14mmx 25mm from memory. If you order the board with 0.8mm fr4(economical) the total height is around 1.7mm, otherwise with 0.1mm flexible polymide the total is about 1mm.

https://drive.google.com/drive/folders/1lldumDr7aOpNCwfE2Vw_DBWkPrt6qRWx?usp=drive_linkView attachment 374811View attachment 374812

Just curious, looking at the layout, where does the "dual MOSFET" come in? I only see one component in the renders that appears to be a MOSFET.

 

[CodyRoseman]

Just curious, looking at the layout, where does the "dual MOSFET" come in? I only see one component in the renders that appears to be a MOSFET.

Bottom right is a Texas Instruments CSD85301Q2

 

[lightninjay]

Bottom right is a Texas Instruments CSD85301Q2

A "single" one, no? Double-mosfet implies two mosfets.

 

[CodyRoseman]

https://www.ti.com/lit/ds/slps521/slps521.pdf

it is two n-channel mosfets built into one package

A "single" one, no? Double-mosfet implies two mosfets.

 

[lightninjay]

https://www.ti.com/lit/ds/slps521/slps521.pdf

it is two n-channel mosfets built into one package

Ahhh! Thank you for the clarification! Admittedly, I've been drinking, since it's an American holiday.

 

[CodyRoseman]

Ahhh! Thank you for the clarification! Admittedly, I've been drinking, since it's an American holiday.

All good, go easy on the drinks

 

[lightninjay]

All good, go easy on the drinks

You may have just inadvertently shown me the new mosfet package which I should do any future installs with, so thanks for that!

 

[cgtchy0412]

https://www.ti.com/lit/ds/slps521/slps521.pdf

it is two n-channel mosfets built into one package

Have you tested it ? seems the RdsOn value is too high, or maybe it can only work with SDA SCL point.

 

[abal1000x]

.

 

[CodyRoseman]

Have you tested it ? seems the RdsOn value is too high, or maybe it can only work with SDA SCL point.

I haven't tested it. The rdson value is well within scope. It is only 3mΩ higher with a of VGS = 4.5V. I = (assuming 1.8v across cap, just a guess) / 0.00002 ohms = 90,000amps vs i = 1.8 / 0.000023 = 78,261amps, negligible for an application that is tdp using 2 amps at max ever.

 

[abal1000x]

.

 

[Smiles]

Can I remove the LDO from rp2040 zero? Also is there maybe issue with latest firmware? Should I stick with 2.65? With duel mosfet do I need pull-down?

 

[lightninjay]

Can I remove the LDO from rp2040 zero? Also is there maybe issue with latest firmware? Should I stick with 2.65?

After flashing, shouldn't be an issue. Also, recommended that you stick with most up-to-date firmware from Rehius here

https://gbatemp.net/threads/picofly-a-hwfly-switch-modchip.622701/page-78#post-10090767

 

[abal1000x]

.

 

[CodyRoseman]

Can I remove the LDO from rp2040 zero? Also is there maybe issue with latest firmware? Should I stick with 2.65? With duel mosfet do I need pull-down?

Yes

Post automatically merged: May 30, 2023

It might not work. I still not yet getting confirmed from someone using TI mosfet.
The characteristics of IRF and AON in this glitch are well tested.
Not yet tested the TI mosfet.

I don't think you quite understand how small the difference is between these mosfets is, I put my money on it working.

 

[Smiles]

Thank you for the reply, seems I edited my comment too late. What about the pull-down? Is it needed with duel mosfet? I didn’t add it on the first mod I performed.