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PicoKey

I go to highschool, and teens are always around when i try to login to my mail or github or any other account, so my password can be compromised.

To solve this, I created PicoKey, which is a hardware pass key in a very small form factor(34.5mm x 18.5mm). It uses the RP2350A chip, although I wanted to use my favourite MCU, the rp2040, it was not safe as a pass key, so I used the rp2350A this time, which is much more safer and secure than the RP2350A.

I think it can also function as a USB-HID device because it has an external button too and 16Mb of memory size.

It has USB-A in the PCB itself soo need for external connectors, however, you either need to order a 2.0mm thick PCB(expensive) or you need to order a 1.6mm PCB(pretty cheap) and make up for the 0.4mm using tape or some other method.

Features:

Small form factor: 3.45cm x 1.85 cm
Uses the latest MCU from Raspberyy Pi, the RP2350AA
Could Potentially have HID Compatibilityy
USB inbuilt the PCBB

Idea taken from @Rudy 's RP2350 hardware key

How to Assemble this PCB?

It is basically a single pcb, so assembling this project means soldering on all the components.

To solder, I would recommend buying a stencil along with the PCBs, or opting for PCBA from your PCB manufacturer, I am using JLC for this, and I will be opting for PCBA, as this is a 2 sided board, it will be much easier for 1 side to be PCBA(bottom side) and other by hand(top side).

The RP2350A is housed on the bottom side along with most of the components, and I have placed easy to solder components on the top, and the small pads for resistors and LED are a little bigger, which would help in soldering by hand.

Why i chose to make this project

I chose to make this project mainly for 2 reasons:

  1. i wanted to have a secure hardware key and didn't wanna sign in using passwords in front of everyone.

  2. I wanted to try out making a 2 sided PCB(where components are on 2 sides), to learn how to make such projects and the learning curve for dual sided PCBs.

Images

final pcb img
final cad 1
final cad 2
final sch img

BOM

ITEM NAME ITEM PRICE FUNCTION URL
Pcb Manufacturing + stencil 23.82 main pcb and smt stencil https://jlcpcb.com
PCB Components 21.1131 components on the PCB https://lcsc.com
Total 44.93 USD

PCB Components Breakdown

Note: There are a few resistors and capacitors, which had very high minimum order quantity(MOQ), about 50 pieces so i had to forcefully include those, which i will be utilising in my next highway projects. And tbh the prices were very less(about $0.02 per piece) so i think it is alright

if DNO is yes, i am not ordering the respective parts and thus i have not included the cost in BOM.

Id Designator Designation MPN Footprint DNO - Do not order MOQ Price Quantity Amount Supplier link
1 C1, C2, C3 4.7u GRM155R61C475KE15D 402 No Yes 0.057 10 0.57 https://lcsc.com/product-detail/Multilayer-Ceramic-Capacitors-MLCC-SMD-SMT_Murata-Electronics-GRM155R61C475KE15D_C426094.html
2 C10, C11, C12, C13, C14, C15, C16, C17, C6, C7, C8, C9 100n GRM155R61H104JE14D 402 Yes - 0 36 0 https://lcsc.com/product-detail/Multilayer-Ceramic-Capacitors-MLCC-SMD-SMT_Murata-Electronics-GRM155R61H104JE14D_C426067.html
3 C18, C19 15p GJM1555C1H150FB01D 402 Yes - 0 6 0 https://lcsc.com/product-detail/Multilayer-Ceramic-Capacitors-MLCC-SMD-SMT_Murata-Electronics-GJM1555C1H150FB01D_C441742.html
4 C4, C5 10u CL21A106KBVNNNE 805 No Yes 0.046 5 0.23 https://lcsc.com/product-detail/Multilayer-Ceramic-Capacitors-MLCC-SMD-SMT_Samsung-Electro-Mechanics-CL21A106KBYQNNE_C2932476.html
5 D1 LED 19-213-GHC-YR1S1N-3T 402 Yes - 0 3 0 https://www.lcsc.com/product-detail/LED-Indication-Discrete_Everlight-Elec-16-213-GHC-YR1S1N-3T_C2980183.html?s_z=n_LED
6 D2 ESDS314DBVR ESD5314DBVR 402 No Yes 0.212 5 1.06 https://lcsc.com/product-detail/ESD-and-Surge-Protection-TVS-ESD_TI-ESDS314DBVR_C1847859.html
7 J1 USB_A - USBPCB On PCB - - - - -
8 L1 3.3u A201610S3R3-101-T 806 No Yes 0.2592 5 1.3 https://lcsc.com/product-detail/Power-Inductors_Abracon-LLC-AOTA-B201610S3R3-101-T_C42411119.html
9 R1 33 RT0402BRD0733RL 402 No Yes 0.0198 50 0.99 https://lcsc.com/product-detail/Chip-Resistor-Surface-Mount_YAGEO-RT0402BRD0733RL_C852729.html
10 R2, R5, R6, R7 1k CRCW040210K0FKEDHP 402 No Yes 0.023 20 0.46 https://lcsc.com/product-detail/Chip-Resistor-Surface-Mount_Vishay-Intertech-CRCW04021K00FKEDHP_C313354.html
11 R3, R4 27 ERJ2GEJ270X 402 Yes - 0 6 0 https://lcsc.com/product-detail/Chip-Resistor-Surface-Mount_PANASONIC-ERJ2GEJ270X_C278580.html
12 SW1, SW2 SW_Push K-PTS810SJMS205MTLFSG SW_SPST_PTS810 No No 0.6 6 3.6 https://lcsc.com/product-detail/Tactile-Switches_C-K-PTS810SJM250SMTRLFS_C116501.html
13 U1 RP2350A-QFN60 RPi2350 QFN-60 No No 1.514 3 4.542 https://www.silverlineelectronics.in/collections/the-raspberry-pi/products/rp2350a-raspberry-pi-microcontroller-chip-in-stock-silverline-india
14 U2 AMS1117S-3.3 AMS1117-3.3 SOT-89-3 No Yes 0.1 5 0.5 https://lcsc.com/product-detail/Voltage-Regulators-Linear-Low-Drop-Out-LDO-Regulators_JSMSEMI-AMS1117S-3-3_C917152.html
15 U3 W25Q128JVS W25Q128JVSIM SOIC-8_5.3x5.3mm_P1.27mm Yes - 0 3 0 https://lcsc.com/product-detail/NOR-FLASH_Winbond-Elec-W25Q128JVSIM_C2613930.html
16 Y1 Crystal_GND24 ABM8-27-T3 Crystal_SMD_3225-4Pin_3.2x2.5mm No No 0.3737 3 1.1211 https://www.lcsc.com/product-detail/Crystals_Abracon-LLC-ABM8-272-T3_C20625731.html?s_z=n_abm8
Shipping 3.74
Handling fee 3
Total 21.1131 USD

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