ESP32 Heater Controller

R

roboticsnerd

Okay. I had to move R4 and J7. Sorry if that messes anything up.
Also. There are still issues. RT6 is only connected on one side. C23. RT4 C25. C14. Countless others are only wired up on one size.
Also, ESP32 devkits have a capacitor? Or resistor? That is wired in so you can flash firmware without the S1 and S2 buttons. And I'm not sure if the buttons are necessary, so I'm happy to save money if we can safely nix them.

flux

I’ll re-check the layout after your R4/J7 move, distinguish PCB airwires from actual schematic one-sided wiring, then evaluate whether BOOT/RESET buttons can be removed in favor of ESP32-S3 native USB auto-download behavior.

flux

Done.
Accomplished:
  • Verified RT6/C25, RT4/C23, C14, and related passives are schematic-connected on both sides; the issue was PCB routing/airwires, not one-sided schematic wiring.
  • Removed optional S1 BOOT and S2 RESET buttons to save BOM/assembly cost.
  • Kept the important ESP32 support: R4 GPIO0 pull-up, R3 EN pull-up, and C11 EN reset-delay cap.
  • Cleaned stale routing from your R4/J7 move and re-routed.
  • Final checked categories are clean: no airwires, dangling traces, copper overlaps, invalid layers, or relevant ERC errors.
Open items:
  • If we want best serviceability, add tiny labeled test pads for GPIO0/BOOT and EN/RESET later; they are cheaper than buttons and useful for recovery.
Suggested next steps:
  1. Visually inspect the routed PCB.
  2. Add/verify GND pours and antenna keepout.
  3. Run full manufacturing DRC before export.
  4. Update firmware/bring-up docs to note USB flashing without BOOT/RESET buttons.
Pours, keepout, docs
Add test pads
Verify GND pours
Check antenna keepout
Update docs
Manufacturing review
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Files

Schematic

Layout

3D View

Board Bring-Up Plan — ESP32 Heater Controller
Prerequisites
Equipment:
  • Current-limited bench supply, DMM, oscilloscope, USB-C current/PD analyzer if available
  • Thermal camera or thermocouples for MOSFETs, MP5036, AP63203, heater connectors, enclosure hot spots
  • 25 Ω, >=5 W dummy loads for each 5 V / 1 W heater channel
  • Computer with PlatformIO and USB serial monitor
Critical safety note: Do not first-power this board from a PD-capable charger until STUSB4500 NVM is proven 5 V-only. A factory/default STUSB4500 configuration can request higher-voltage PDOs, which would be destructive because the downstream rail is designed as 5 V.
1. Visual Inspection
  • Inspect USB-C pins on J1 for bridges and shell shorts.
  • Inspect U2 STUSB4500, U4 MP5036, U3 AP63203, U1 ESP32-S3 module, Q1-Q4 MOSFET orientation, and all polarized parts.
  • Confirm heater terminal blocks J2-J5 are oriented consistently and soldered cleanly.
  • Confirm no metal debris near USB-C, heater terminals, or buck converter.
  • Confirm ESP32 antenna edge/keepout is respected once layout is complete.
2. Power Rail Verification

Table

RailSourceExpected VoltageToleranceMeasure AtInitial Current LimitPass Criteria
VBUS_RAWUSB-C J1 / bench supply5.0 V+/-5%J1 VBUS, U4 VIN50-100 mA logic-onlyStable 5 V, no overheating
5V_PROTECTEDU4 MP5036 eFuse output5.0 V minus small drop+/-5%J2-J5 pin 1, U3 VIN50-100 mA first, then stagedTracks VBUS, no eFuse cycling
3V3U3 AP63203 buck output3.3 V+/-5%U1 3V3, J6 pin 2, J7 pin 250-100 mA first3.135-3.465 V, low ripple
STUSB_VREG_2V7U2 internal regulator~2.7 VDatasheet limitU2 decoupling capLogic-onlyPresent when U2 powered
STUSB_VREG_1V2U2 internal regulator~1.2 VDatasheet limitU2 decoupling capLogic-onlyPresent when U2 powered
Procedure:
  1. With power off, measure resistance from VBUS_RAW, 5V_PROTECTED, and 3V3 to GND.
  2. Measure each HEATERx_LOW node to GND and to 5V_PROTECTED to catch MOSFET or connector shorts.
  3. Leave all heaters disconnected for first power.
  4. Apply 5.0 V from a current-limited bench supply or known non-PD 5 V USB source.
  5. Start at 50-100 mA. If rails are valid, increase to 200 mA, 500 mA, 1 A, 1.5 A, and only later 2 A.
  6. Verify U4 current limit behavior near the design target (~2 A from R1 = 1.1 kΩ) only with dummy loads and thermal monitoring.
3. Critical Signal Verification

Table

SignalNetExpected StateMeasure AtNotes
ESP32 enableESP_ENHigh during run, low when S2 pressedU1 ENR3 10k pull-up, C11 reset cap
ESP32 bootESP_BOOTHigh during normal boot, low when S1 pressedU1 GPIO0R4 10k pull-up
Heater gate 1HEATER1_GATE / HEATER1_PWMLow at reset and bootQ1 gate, U1 GPIO10Verify no ROM boot pulse turns heater on
Heater gate 2HEATER2_GATE / HEATER2_PWMLow at reset and bootQ2 gate, U1 GPIO11Verify no ROM boot pulse turns heater on
Heater gate 3HEATER3_GATE / HEATER3_PWMLow at reset and bootQ3 gate, U1 GPIO12Verify no ROM boot pulse turns heater on
Heater gate 4HEATER4_GATE / HEATER4_PWMLow at reset and bootQ4 gate, U1 GPIO13Verify no ROM boot pulse turns heater on
I2CI2C_SCL/I2C_SDAIdle high at 3.3 VJ6 pins 4/3R7/R6 4.7k pull-ups
PD alertPD_ALERTNormally high, low on alertU1 GPIO38 / U2 ALERTR8 4.7k pull-up
Procedure:
  1. Scope all heater PWM/gate pins during power ramp, reset button press, bootloader entry, firmware upload, brownout, and eFuse recovery.
  2. Confirm firmware initializes GPIO10-GPIO13 low before any heater is connected.
  3. Confirm I2C bus idles high and scans U2 STUSB4500 at expected address 0x28.
4. Connector and Interface Tests

Table

ConnectorTypePins to VerifyTest Method
J1USB-CVBUS_RAW, GND, CC1/CC2, USB_D_P/NContinuity, USB enumeration, ESD part orientation
J2Heater 1 terminal5V_PROTECTED, HEATER1_LOWDummy load at 25 Ω, PWM test
J3Heater 2 terminal5V_PROTECTED, HEATER2_LOWDummy load at 25 Ω, PWM test
J4Heater 3 terminal5V_PROTECTED, HEATER3_LOWDummy load at 25 Ω, PWM test
J5Heater 4 terminal5V_PROTECTED, HEATER4_LOWDummy load at 25 Ω, PWM test
J6Qwiic I2CGND, 3V3, SDA, SCLI2C scan, OLED/display test
J7UART/debugGND, 3V3, TXD0, RXD03.3 V UART echo/debug
5. Programming and Debug Interface

Table

InterfaceSignalsConnectorTool
Native USBUSB_D_P, USB_D_NJ1 USB-CPlatformIO / esptool
Boot buttonsESP_BOOT, ESP_ENS1, S2Manual bootloader entry
UART fallbackUART_TXD0, UART_RXD0J73.3 V USB-UART adapter
Procedure:
  1. Power board at 5 V current-limited, heaters disconnected.
  2. Flash safe firmware that initializes all heater pins low.
  3. If USB enumeration fails, hold S1/BOOT, press and release S2/EN, then release S1.
  4. Confirm serial output at 115200 baud.
  5. Confirm I2C scan reports STUSB4500 and any display connected to J6.
6. Functional Validation

Table

TestComponentsInputExpected OutputPass Criteria
Safe bootU1, Q1-Q4Power cycle/resetHeater PWM lowAll heater gates remain low
NTC readbackRT1-RT6Room temperaturePlausible ADC temperaturesAll readings within room temp +/- expected tolerance
NTC fault openRT1-RT6Simulate openFault stateHeaters disabled/latch off
NTC fault shortRT1-RT6Simulate short to GNDFault stateHeaters disabled/latch off
EncoderSW1Rotate/pushCounts/button state changesNo false stuck state
LEDsD2-D4Firmware color testRGB indicatorsCorrect active-low behavior
Heater channel 1Q1/J225 Ω dummy loadPWM current modulation0%, 10%, 50%, 100% work
Heater channel 2Q2/J325 Ω dummy loadPWM current modulation0%, 10%, 50%, 100% work
Heater channel 3Q3/J425 Ω dummy loadPWM current modulation0%, 10%, 50%, 100% work
Heater channel 4Q4/J525 Ω dummy loadPWM current modulation0%, 10%, 50%, 100% work
All heatersQ1-Q4/J2-J5Four dummy loads~0.8 A heater loadRails stable, components cool
WiFi loadU1WiFi activeNo brownout3V3 stable during RF peaks
PD 5 V sourceU2/J1PD charger after NVM verification5 V contract onlyVBUS remains 5 V
7. Expected Measurements Reference

Table

MeasurementLocationExpected ValueInstrument
USB inputVBUS_RAW to GND5.0 VDMM/scope
Protected heater rail5V_PROTECTED to GND~5.0 VDMM/scope
Logic rail3V3 to GND3.3 VDMM/scope
Heater current per channelJ2-J5 with 25 Ω load~200 mA at 100%DMM/current probe
Total heater current5V_PROTECTED source~800 mA at 4 channels 100%Current probe/supply
MOSFET temperatureQ1-Q4Comfortably below package limitThermal camera
eFuse temperatureU4No thermal cycling at normal loadThermal camera
Buck temperatureU3/L1Stable under WiFi/display loadThermal camera
8. Destructive-Risk Tests to Run Carefully
Use current-limited supply and dummy loads first:
  • 0.5 A, 0.9 A, 1.5 A, and 2.0 A source limit behavior.
  • Heater connector short to GND.
  • MOSFET drain-source short simulation.
  • Long heater leads with PWM to observe ringing/EMI.
  • Unplug/replug USB with heaters previously commanded on.
  • Brownout/eFuse cycling recovery.
Pass/Fail Summary

Table

Test SectionResultNotes
Visual Inspection[ ] Pass / [ ] Fail
Power Rails[ ] Pass / [ ] Fail
Critical Signals[ ] Pass / [ ] Fail
Connectors[ ] Pass / [ ] Fail
Programming[ ] Pass / [ ] Fail
Functional Validation[ ] Pass / [ ] Fail
Thermal Validation[ ] Pass / [ ] Fail
Fault Tests[ ] Pass / [ ] Fail
Board Status: [ ] Ready for deployment / [ ] Requires rework

  • Prerequisites

  • 1. Visual Inspection

  • 2. Power Rail Verification

  • 3. Critical Signal Verification

  • 4. Connector and Interface Tests

  • 5. Programming and Debug Interface

  • 6. Functional Validation

  • 7. Expected Measurements Reference

  • 8. Destructive-Risk Tests to Run Carefully

  • Pass/Fail Summary