DIY Dashboard Compass Project
Thought for 23 sec
You’re right to ask. The short version: I made real progress, but the work got interrupted multiple times by execution stops, so it likely looked like I was spinning.
Here’s what actually happened:
Table
| Area | What I did | Current state |
|---|---|---|
| Project setup | Renamed the project and updated the description to match the FJ Cruiser solar compass concept | Done |
| Architecture notes | Created Design Notes for the system intent | Done |
| Major components | Added the MCU, magnetometer, LED driver, charger, LDO, displays, dimmer/switch, connectors, protection, and passives | Done |
| Power wiring | Wired solar input through fuse, Schottky reverse protection, TVS clamp, charger input, battery, charger SYS output, switched rail, and 3.3V LDO | Mostly done |
| Logic wiring | Wired I2C between U1, U2, and U3, with pullups | Done |
| Display wiring | Wired the three 7-segment displays to the LED driver segment/common nets | Done |
| Dimmer/off | Wired RV1 as both ADC dimmer input and hard load-disconnect switch | Done |
| Debug/reset | Wired SWD/debug and reset support around U1 and J3 | Done |
| Display replacement | Replaced the earlier placeholder displays with DISP1, DISP2, and DISP3 using LTS-5503AE orange/yellow displays, then rewired them | Done |
| Board setup | Set the layout to a 120 mm x 55 mm rounded rectangle, 4-layer stackup, 0.2 mm keepout, and 0.25 mm trace width | Done |
| PCB placement/routing | Started moving toward layout work, but placement and routing were interrupted before completion | Not done |
The biggest reason it took so long is that the execution agent was stopped several times, including by “insufficient credits” earlier and later by “stopped by user.” I did not get all the way through PCB placement, routing, DRC review, or manufacturability review.
Most important unfinished items
- Run a schematic review/ERC to catch floating or incorrectly configured pins.
- Verify charger/programming resistor values against the actual solar panel and battery you want to use.
- Place components on the PCB.
- Route the board.
- Run DRC and review footprints/MPNs.
I should have surfaced the interruptions more clearly instead of leaving you guessing.
Recent activity log
Check recent changes
Run design checks
Modified components
Export BOM
Refine this doc
Ask about this doc
Design Notes
Project
Dashboard-mounted automotive compass for Toyota FJ Cruiser.
Architecture decisions
- Use a 3-axis I2C magnetometer for heading sensing.
- Use a low-power MCU to read the compass, compute N/E/S/W/NE/NW/SE/SW text, read dimmer voltage, and control display brightness.
- Use an I2C LED display driver to reduce MCU pin count for three amber/yellow 7-segment digits.
- Use a single-cell LiPo energy store with solar charging and 3.3V regulation.
- Use a switch-pot dimmer as both user brightness control and hard/off input.
- Include automotive-style input protection and decoupling even though the main charge source is solar.
Schematic wiring completed
- Solar input path: J1 pin 1 -> F1 -> D2 -> CHG_IN -> U4 IN.
- Input protection: D1 TVS and C7/C5 capacitance from CHG_IN to GND after reverse protection.
- Battery path: U4 BAT -> J2 pin 1 with C12 BAT bypass to GND.
- System path: U4 SYS -> RV1 switch -> U5 input -> 3.3V logic rail.
- Dimmer: RV1 potentiometer forms a 3.3V to GND divider; wiper goes to U1 PA02 as DIMMER_ADC.
- I2C bus: U1 PA22/PA23 connect to U2 and U3 with R1/R2 4.7k pull-ups to 3.3V.
- Debug: J3 follows ARM 2x5 SWD convention with VTref, SWDIO, SWCLK, RESET, and GND.
- Display matrix: U3 CA1-CA8 drive shared segment nets a, b, c, d, e, f, g, dp. U3 CB1-CB3 select digit commons for DISP1-DISP3.
Charger configuration
- U4 BQ25185 is configured for a protected single-cell LiPo pack.
- R3 = 6k on ISET targets about 50mA fast charge current using KISET typical 300AΩ.
- R4 = 18k on ILIM/VSET sets 4.2V battery regulation and 500mA input current limit per BQ25185 datasheet table.
- R11 currently holds TS/MR high because no battery NTC connector/network is fitted. For production, replace this with a battery NTC network or a battery pack with appropriate temperature monitoring.
- U4 ~CE is tied low so charging remains enabled while solar input is present.
Support passives added
- R5/C10: reset pull-up/filter for U1 ~RESETN.
- R6/R7: SWDIO pull-up and SWCLK pull-down.
- R8/C13: U3 R_EXT and C_FILT support network.
- R9/R10: U4 STAT1/STAT2 pull-ups for MCU monitoring.
- C11: U1 VDDCORE capacitor.
- C12: U4 BAT bypass capacitor.
- C14: U2 C1 support capacitor.
Layout intent
- Rectangular dashboard board with three displays centered and aligned for visibility.
- Dimmer/off knob placed at the right edge for driver access.
- Solar and battery connectors placed at board edges.
- Magnetometer placed away from high-current LED traces, power/protection parts, ferrous hardware, and mounting screws.
- LED driver placed near the displays to keep segment/common traces short.
- Charger, fuse, TVS, and battery connector grouped together near the power-entry edge.
Open engineering notes
- The current display parts are accepted as library-available amber/orange placeholders.
- The current switch-pot is accepted for schematic/layout progress, but its mechanical fit should be confirmed against the final dashboard enclosure.
- Add mounting holes only after confirming dashboard bracket/enclosure constraints.
- A real battery NTC network is recommended before field use if the selected LiPo pack does not already provide protected/temperature-monitored charging behavior.
Project
Architecture decisions
Schematic wiring completed
Charger configuration
Support passives added
Layout intent
Open engineering notes
