Schematic Design Assistance

yari4embedded

yari4embedded

Please fix exactly these two issues and nothing else: 1) Add a test pad component on net FP_OTP_TP_ONLY so fingerprint OTP J1:3 has an actual test pad, as originally specified. 2) Add a 10 kOhm pullup resistor from net IRQ_SHARED_GPIO3 to 3V3, since MPR121 IRQ and TCA9534A INT are open-drain and the line currently has no pullup. Do not change any GPIO assignments, nets, or other components. BNO055 ADR is fine as-is (module handles addressing internally). After the fixes, re-run ERC and confirm both changes.

flux

I’ll make only those two schematic fixes: add an OTP test pad to FP_OTP_TP_ONLY and add a 10 kΩ pullup from IRQ_SHARED_GPIO3 to 3V3, then rerun ERC.

flux

Done — made only the two requested schematic changes.
Confirmed:
  • Added TP37 to fingerprint OTP net FP_OTP_TP_ONLY; it is associated with J1:3 / OTP test-only connectivity.
  • Added R31 = 10kΩ pullup:
    • R31:P1 → 3V3
    • R31:P2 → IRQ_SHARED_GPIO3
    • IRQ_SHARED_GPIO3 contains U1:GPIO3, U2:IRQ, U5:~{INT}, and R31:P2.
ERC re-run result: no ERROR, WARNING, or OPEN checks returned.
Review, document, layout
Run schematic review
Update project notes
Start PCB placement
Check BOM availability
LED4
LED1
LED3
LED2
U4
U2
C13
Capacitance
10uF
TP32
TP23
TP3
TP9
TP4
TP18
TP11
TP14
TP20
TP7
TP5
C16
Capacitance
Capacitance
TP10
TP29
C14
Capacitance
0.1uF
TP17
TP21
C15
Capacitance
Capacitance
TP15
TP30
C6
Capacitance
0.1uF
TP37
TP35
TP13
TP8
TP12
C8
Capacitance
1.0uF
TP24
TP6
TP19
TP34
TP22
TP1
TP25
TP36
C10
Capacitance
0.1uF
TP31
C7
Capacitance
0.1uF
TP2
C12
Capacitance
100uF
C5
Capacitance
0.1uF
TP26
C9
Capacitance
0.1uF
TP28
TP33
C11
Capacitance
0.1uF
TP27
TP16
OLED1
J2
R18
Resistance
0Ω
R17
Resistance
0Ω
R22
Resistance
1.0kΩ
R14
Resistance
0Ω
R15
Resistance
0Ω
R20
Resistance
0Ω
R7
Resistance
4.7kΩ
R27
Resistance
500 Ω
R25
Resistance
10kΩ
R10
Resistance
0Ω
R11
Resistance
0Ω
R31
Resistance
10kΩ
R29
Resistance
500 Ω
R24
Resistance
10kΩ
R6
Resistance
4.7kΩ
R8
Resistance
75kΩ
R12
Resistance
0Ω
R23
Resistance
10kΩ
R19
Resistance
0Ω
R30
Resistance
500 Ω
R28
Resistance
500 Ω
R26
Resistance
10kΩ
R13
Resistance
0Ω
R21
Resistance
330Ω
R9
Resistance
0Ω
R16
Resistance
0Ω
J1
U1
U3
U5
SW4
D1
SW1
SW2
SW3

Refine this doc
Ask about this doc
BlackStar Remote V0 — Schematic Notes
Scope
Schematic-only prototype implementation. PCB placement/routing intentionally not started.
Controller GPIO Plan
  • GPIO4: I2C SDA
  • GPIO5: I2C SCL
  • GPIO3: shared open-drain IRQ from MPR121 and TCA9534A INT
  • GPIO20: ESP RX from fingerprint UART_TX
  • GPIO21: ESP TX to fingerprint UART_RX
  • GPIO7: fingerprint TOUCHOUT input
  • GPIO6: RGB ring SK6812 data via 330 Ω series resistor
  • GPIO8: onboard/status LED test pad only
  • GPIO10: spare/test pad
  • GPIO18/GPIO19 not used; GPIO9 marked NC/not used for user buttons.
Major Components
  • U1: ESP32-C3 SuperMini SMD module
  • U2: custom MPR121QR2 component created from NXP datasheet, 20-QFN 3 × 3 mm, 0.4 mm pitch
  • U3: DRV2605LDGST haptic driver
  • U4: BNO055 I2C 3.3 V module/sublayout
  • U5: TCA9534APWR GPIO expander
  • J1: Molex 5052781233 12-pin 0.5 mm bottom-contact FPC for Q Tech F6B27_C fingerprint sensor
  • LED1–LED4: SK6812MINI-E RGB LEDs
  • OLED1: optional SSD1306 I2C OLED module, DNI
Address / Bus Assumptions
  • MPR121 ADDR tied to 3V3 for 0x5B.
  • DRV2605L expected at 0x5A.
  • BNO055 expected at 0x28.
  • Optional SSD1306 OLED expected at 0x3C.
  • TCA9534A A0/A1/A2 tied low for 0x20.
  • Only one effective I2C pullup set installed: R6/R7 = 4.7 kΩ to 3V3.
Fingerprint FPC Mapping
J1 follows requested F6B27_C 12-pin mapping: 1 GND, 2 GND, 3 OTP test pad only, 4 UART_RX from ESP GPIO21, 5 UART_TX to ESP GPIO20, 6 VCC3V3, 7 VDDS, 8 TOUCHOUT to ESP GPIO7, 9–12 GND.
MPR121 Electrode Mapping
R9–R20 are 0 Ω/debug isolation jumpers:
  • E0 Up
  • E1 Upper-right
  • E2 Right
  • E3 Lower-right
  • E4 Down
  • E5 Lower-left
  • E6 Left
  • E7 Upper-left
  • E8–E11 spare/test pads
Layout note: keep copper/ground pour away from touch electrode pads/traces and use guard/clearance strategy during PCB layout.
Open Mechanical / Footprint Checks
  • Verify Q Tech F6B27_C flex pitch, contact side, stiffener orientation, and required FPC connector contact orientation before PCB layout.
  • Confirm OLED module supply tolerance if OLED1 is populated; current schematic connects its module pin named 5V to 3V3 to preserve 3.3 V-only prototype operation.
  • Confirm haptic motor type/current against DRV2605L mode and JST-PH connector/cable choice.
BOM Suggestions
  • MPR121QR2: custom part from NXP datasheet; note MPR121 appears archived/discontinued, so availability risk exists.
  • FPC: Molex 5052781233, 12-position 0.5 mm bottom-contact right-angle SMT.
  • RGB: SK6812MINI-E preferred for 3.3 V data compatibility.
  • Button pullups R23–R26 may be DNI if firmware enables reliable TCA9534A/internal pullups or alternate expander pullups.
Firmware Bring-up Notes
  1. Confirm 3V3 rail current headroom before enabling RGB full-white.
  2. Scan I2C for 0x20, 0x28, 0x5A, 0x5B, and optional 0x3C.
  3. Configure GPIO3 as input with pullup if required; both MPR121 IRQ and TCA9534A INT are open-drain/shared.
  4. Configure fingerprint UART on GPIO20/GPIO21 and verify TOUCHOUT on GPIO7.
  5. Initialize SK6812 on GPIO6 at conservative brightness.

  • Scope

  • Controller GPIO Plan

  • Major Components

  • Address / Bus Assumptions

  • Fingerprint FPC Mapping

  • MPR121 Electrode Mapping

  • Open Mechanical / Footprint Checks

  • BOM Suggestions

  • Firmware Bring-up Notes

Documents

Assets

Assets are files uploaded to this project which can be used in various ways.

BlackStar_Remote_V0 thumbnail
Welcome to your new project. Imagine what you can build here.

Properties

Properties describe core aspects of the project.

Pricing & Availability

Distributor

Qty 1

Arrow

$4.14–$5.89

Digi-Key

$6.96

HQonline

$4.80

LCSC

$19.43

Mouser

$24.70–$87.01

TME

$0.00

Verical

$97.11–$106.33

Controls