Schematic Design Assistance
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.
Thought for 6 sec
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.Worked for 1 min 42 sec
Done — made only the two requested schematic changes.
Confirmed:
- Added
TP37to fingerprint OTP netFP_OTP_TP_ONLY; it is associated withJ1:3/ OTP test-only connectivity. - Added
R31 = 10kΩpullup:R31:P1→3V3R31:P2→IRQ_SHARED_GPIO3IRQ_SHARED_GPIO3containsU1:GPIO3,U2:IRQ,U5:~{INT}, andR31:P2.
ERC re-run result: no
ERROR, WARNING, or OPEN checks returned.Review, document, layout
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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
- Confirm 3V3 rail current headroom before enabling RGB full-white.
- Scan I2C for 0x20, 0x28, 0x5A, 0x5B, and optional 0x3C.
- Configure GPIO3 as input with pullup if required; both MPR121 IRQ and TCA9534A INT are open-drain/shared.
- Configure fingerprint UART on GPIO20/GPIO21 and verify TOUCHOUT on GPIO7.
- 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
