+-----------------------------------------------------------------------+
|  ESP32-DevKitC-V4  ---  analog-node                                   |
+-----------------------------------------------------------------------+
|  Rails: 5V, 3V3, GND                                                  |
|                                                                       |
|  ext_adc  [ADS1115 4-channel 16-bit ADC hub (I2C)]  -- External ADC   |
|    VCC   -> rail 3V3                                                  |
|    GND   -> rail GND                                                  |
|    SDA   -> i2c0 (GPIO21)                                             |
|    SCL   -> i2c0 (GPIO22)                                             |
|                                                                       |
|  panel_v  [ADS1115 channel]  -- Solar panel voltage                   |
|                                                                       |
|  shunt_i  [ADS1115 channel]  -- Battery shunt current                 |
|                                                                       |
|  rail_v  [Generic analog input]  -- Board 3V3 rail                    |
|    IN    -> GPIO34                                                    |
|                                                                       |
|  Passives:                                                            |
|    c1: 100nF capacitor, ext_adc.VCC  <->  GND   (decoupling ext_adc)  |
|    r1: 4.7k resistor, i2c0.SDA  <->  3V3   (I2C pull-up)              |
|    r2: 4.7k resistor, i2c0.SCL  <->  3V3   (I2C pull-up)              |
|                                                                       |
|  BOM:                                                                 |
|    - ESP32-DevKitC-V4                                                 |
|    - ADS1115 4-channel 16-bit ADC hub (I2C)  (ext_adc)                |
|    - ADS1115 channel  (panel_v)                                       |
|    - ADS1115 channel  (shunt_i)                                       |
|    - Generic analog input  (rail_v)                                   |
|    - 1x 100nF capacitor                                               |
|    - 2x 4.7k resistor                                                 |
|                                                                       |
|  Power: ~1mA typical, ~2mA peak (budget 500mA)  OK                    |
|                                                                       |
|  Warnings: none                                                       |
+-----------------------------------------------------------------------+
