First version getting ready to release

2026-06-16 04:45:59 +10:00
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+# Connecting an ESP32 to the SP PRO serial port
+
+The SP PRO serial port is **RS-232** (±12 V signalling), not RS-485 and not logic-level
+UART. You therefore **must** put an RS-232 ↔ 3.3 V level shifter between the inverter and
+the ESP32 — wiring the SP PRO directly to an ESP32 GPIO will damage the ESP32.
+
+Reference: Selectronic Tech Note
+[TN0050 "SP PRO Serial Port Pin-out"](https://www.selectronic.com.au/documents/TechNotes/TN0050_02%20SP%20PRO%20Serial%20Port%20Pin-out.pdf),
+cross-checked with the [selpi `connecting.md`](https://github.com/neerolyte/selpi/blob/main/docs/connecting.md)
+(which connects via an FT232 USB-to-RS232 cable at 57600 baud).
+
+## SP PRO RJ45 pinout (TN0050)
+
+| RJ45 pin | Signal | Use |
+|---|---|---|
+| 1 | +12 V isolated (1 A) | optional supply — **do not** feed the ESP32 directly |
+| 2 | DTR | not needed |
+| **3** | **TXD** | SP PRO → us |
+| **4** | **GND** | common ground (required) |
+| 5 | GND | ground (redundant) |
+| **6** | **RXD** | us → SP PRO |
+| 7 | DCD | not needed |
+| 8 | — | not connected |
+
+Only **TXD, RXD and GND** are needed. Settings: **57600 baud, 8N1, no flow control.**
+
+## Level shifter: MAX3232
+
+A **MAX3232** (3.3 V RS-232 transceiver with internal charge pump) is the right part —
+it is the 3.3 V-capable successor to the MAX232. RS-485 transceivers (MAX3485 etc.) are
+**not** suitable here. Add the four 0.1 µF charge-pump capacitors per its datasheet.
+
+## Wiring
+
+```
+  SP PRO (RS-232)            MAX3232                 ESP32 (3.3V UART2)
+  ---------------           ---------               ------------------
+  RJ45 pin 3  TXD  ------->  R1IN
+                             R1OUT  ------------->   GPIO16  (RX2)
+  RJ45 pin 6  RXD  <-------  T1OUT
+                             T1IN   <-------------   GPIO17  (TX2)
+  RJ45 pin 4  GND  -------+- GND ----------------+-  GND   (common!)
+                          |                      |
+  3.3V  ----------------- VCC                    (4x 0.1uF charge-pump caps)
+```
+
+- **TXD of one side always goes to RXD of the other** — note the crossover above.
+- **Common ground is mandatory.** RS-232 is single-ended and needs a shared reference.
+- RS-232 has no direction-control line (unlike RS-485), so there is nothing equivalent to
+  DE/RE to manage.
+
+## ESP32 UART
+
+Use **UART2** to keep UART0 free for USB logging/flashing:
+
+```cpp
+Serial2.begin(57600, SERIAL_8N1, /*RX=*/16, /*TX=*/17);
+```
+
+GPIO16/17 are safe general-purpose pins on most ESP32 dev boards. (On a few modules with
+PSRAM these pins are reserved — pick two other free UART-capable GPIOs and update the
+sketch if so.) See `esp32/sppro_esp32.ino`.
+
+## Quick bring-up checks
+
+1. Confirm the SP PRO serial port is enabled and note its **baud** and **password**
+   (front panel → Settings → Communications).
+2. Loopback-test the MAX3232: short its TTL TX→RX and echo bytes through the ESP32.
+3. With it wired to the SP PRO, the first query at `0xa000` should echo back; the
+   `sppro-console` demo (or the sketch) will report "connected" once login succeeds.
+4. If login fails, the usual causes are wrong/blank password, swapped TX/RX, or missing
+   common ground.