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Move the Nano link to Serial2, update READMEs
- ESP32 talks to the Nano on UART2 (GPIO 17 TX / GPIO 16 RX); Serial (USB) is now free for debug output and boot messages no longer reach the Nano - README: wiring table, actual schedule (clock from 08:00), TODO section for the rewiring Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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@@ -23,17 +23,17 @@ See README.md for the overview.
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- **Nano RAM is tight** (ATmega328P, 2 KB). The frame buffers are allocated with
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`calloc`. Avoid `String`, large stack buffers and new globals in Nano code. Put constant
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data in `PROGMEM`.
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- The Nano and the ESP32 share one UART. On the ESP32, `Serial` is the display link, so
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**don't print debug output on the ESP32's `Serial`**: the Nano would read it as
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commands. The Nano ignores unknown command bytes, but text that starts with
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s/S/F/D/P/B/R/T will be run as a command.
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- The ESP32 talks to the Nano on `Serial2` (`nanoSerial` in `libs.h`, GPIO 17 TX / GPIO 16
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RX). `Serial` (UART0/USB) is free for debug output. Never write debug text to
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`nanoSerial`: the Nano runs lines that start with s/S/F/D/P/B/R/T as commands.
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- Open hardware TODOs are listed in the README `TODO` section. Update it when one is done.
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- `src/esp32/secrets.h` holds the real credentials and is gitignored. Never commit it.
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Add new secrets to `secrets.example.h` as placeholders.
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- The relay (ESP32 GPIO 13, `LOW` = on) powers both the panels and the Nano. Each time it
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switches on, the Nano cold-boots and then sends `READY`. The ESP's `relayOn()` waits for
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that message, at most `NANO_BOOT_TIMEOUT`. The timeout also covers the case where the
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Nano's TX isn't wired to the ESP's RX.
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- `relayOff()` ends `Serial` and sets the TX pin to input. Otherwise the idle-high TX line
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- `relayOff()` ends `nanoSerial` and sets its TX pin to input. Otherwise the idle-high TX line
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powers the Nano through its RX pin. Never send display commands while `relay_on` is
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false.
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- The Nano keeps no state over a power cycle except the flip time in EEPROM. The driver
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@@ -68,21 +68,34 @@ pio device monitor -e nano # serial monitor
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In VS Code you can also pick the environment in the PlatformIO status bar.
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> **Tip:** The Nano and the ESP32 share a serial line. Disconnect the ESP32 TX → Nano RX
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> wire before you flash the Nano over USB, or the upload may fail.
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> **Tip:** The ESP32 → Nano wire goes to the Nano's RX pin, which the Nano's USB chip
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> also uses. Disconnect that wire before you flash the Nano over USB, or the upload may
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> fail.
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## Wiring between ESP32 and Nano
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The ESP32 talks to the Nano on **UART2** (`Serial2`, 115200 baud). The ESP32's own
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`Serial` (UART0, USB) is free for debug output.
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| ESP32 | Nano | Notes |
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|-------|------|-------|
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| GPIO 17 (TX2) | D0 (RX) | Display commands |
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| GPIO 16 (RX2) | D1 (TX) | `READY` and `ERR` replies. Use a 5 V → 3.3 V voltage divider (e.g. 1 kΩ / 2 kΩ), because the ESP32 is not 5 V tolerant. Optional: without it, the ESP waits a fixed 3 s after power-on. |
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| GND | GND | Common ground |
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| GPIO 13 | Relay input | Relay powers the panels and the Nano (`LOW` = on) |
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## How it works
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1. **ESP32 boot.** The ESP32 connects to WiFi and starts ArduinoOTA. After a crash or
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unexpected reset it stays in an *OTA panic window* for 15 seconds, so you can flash a
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fix before the main code runs again. It then switches the display relay on, starts NTP
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and connects to MQTT.
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fix before the main code runs again. It then switches the display relay on, waits for
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the Nano's `READY` message (at most 3 s), starts NTP and connects to MQTT.
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2. **Clock loop (every second).**
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- **07:00–22:00:** Pikachu with a thought bubble showing `HH:MM`. A yawning Pikachu is
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- **08:00–22:00:** Pikachu with a thought bubble showing `HH:MM`. A yawning Pikachu is
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shown from 17:00.
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- **22:00–23:30:** the clock is only drawn on the quarter hour. In between, the relay
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turns the display off.
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- **Night:** the screen is cleared and power is cut after 30 seconds.
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- **22:00–23:30:** the clock is only shown during the minutes :00, :15, :30 and :45.
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30 seconds after each of those minutes, the relay turns the display off.
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- **23:31–08:00:** the screen is cleared and power is cut after 30 seconds.
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3. **Home Assistant switches** (MQTT discovery):
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- `FlipDot Display Clock`: off shows a Nintendo logo instead of the clock.
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- `FlipDot Display Power`: off clears the display and cuts power through the relay.
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@@ -91,3 +104,15 @@ In VS Code you can also pick the environment in the PlatformIO status bar.
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to fix dots that did not flip.
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The serial protocol is described in [src/nano/README.md](src/nano/README.md).
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## TODO
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- [ ] **Rewire the Nano link to UART2.** The firmware now uses `Serial2` (GPIO 16/17)
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instead of `Serial` (GPIO 1/3). Move the ESP32 TX wire from GPIO 1 to **GPIO 17** before
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you flash this firmware, or the display gets no data. See
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[Wiring between ESP32 and Nano](#wiring-between-esp32-and-nano).
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- [ ] **Add the reply wire:** Nano D1 (TX) → voltage divider → ESP32 GPIO 16 (RX2). With it,
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the ESP sends the first frame as soon as the Nano is ready, instead of after 3 s.
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- [ ] **Check the boot timing.** Build the Nano with `MEASURE_REFRESH` to see how long a
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full redraw takes. If the reply wire isn't fitted, check that 3 s
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(`NANO_BOOT_TIMEOUT`) is enough for the Nano to boot.
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+6
-5
@@ -3,8 +3,9 @@
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PlatformIO environments: `esp32` (OTA) and `esp32_usb` (USB)
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The ESP32 decides what is shown on the display. It never touches the panel itself. The
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BROSE9323 driver is built with `-D ESPSERIAL`, so every GFX call is sent over `Serial`
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(115200 baud) to the Nano.
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BROSE9323 driver is built with `-D ESPSERIAL`, so every GFX call is sent to the Nano over
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`Serial2` (UART2, GPIO 17 TX / GPIO 16 RX, 115200 baud). `Serial` (USB) is only used for
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debug output. Wiring is described in the [main README](../../README.md#wiring-between-esp32-and-nano).
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## Files
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@@ -40,10 +41,10 @@ BROSE9323 driver is built with `-D ESPSERIAL`, so every GFX call is sent over `S
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| Time | Display |
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|------|---------|
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| 07:00 – 17:00 | Pikachu and the clock, updated every minute |
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| 08:00 – 17:00 | Pikachu and the clock, updated every minute |
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| 17:00 – 22:00 | Yawning Pikachu and the clock |
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| 22:00 – 23:30 | Clock drawn only on the quarter hour; power is off in between |
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| night | Screen cleared, power off |
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| 22:00 – 23:30 | Clock shown only during the minutes :00, :15, :30 and :45; power is off in between |
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| 23:31 – 08:00 | Screen cleared, power off |
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## Adding bitmaps
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+4
-1
@@ -45,7 +45,10 @@ bool power = true;
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const int led1 = BUILTIN_LED; // Pin of the LED
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const int relay = 13; // Pin of the relay, powers the panels and the Nano (LOW = on)
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const int nano_tx = 1; // UART0 TX, wired to the Nano RX
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// Link to the Nano on UART2. Serial (UART0) stays free for USB / debug output.
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HardwareSerial &nanoSerial = Serial2;
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const int nano_rx = 16; // UART2 RX, wired to the Nano TX (through a 5V -> 3.3V divider)
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const int nano_tx = 17; // UART2 TX, wired to the Nano RX
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bool relay_on = false;
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// Max wait for the Nano's READY after power on (also the wait when Nano TX is not wired to our RX)
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const uint32_t NANO_BOOT_TIMEOUT = 3000;
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+8
-8
@@ -14,9 +14,9 @@ void waitForNano()
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uint32_t start = millis();
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while (millis() - start < NANO_BOOT_TIMEOUT)
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{
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while (Serial.available())
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while (nanoSerial.available())
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{
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char c = Serial.read();
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char c = nanoSerial.read();
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if (c == '\n')
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{
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line[len] = '\0';
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@@ -39,10 +39,10 @@ void relayOn()
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if (relay_on)
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return;
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Serial.begin(115200);
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nanoSerial.begin(115200, SERIAL_8N1, nano_rx, nano_tx);
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// drop old data (e.g. ERR replies) so only a new READY counts
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while (Serial.available())
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Serial.read();
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while (nanoSerial.available())
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nanoSerial.read();
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digitalWrite(relay, LOW);
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waitForNano();
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@@ -55,8 +55,8 @@ void relayOff()
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relay_on = false;
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// An idle UART TX line is high and would power the Nano through its RX pin
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Serial.flush();
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Serial.end();
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nanoSerial.flush();
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nanoSerial.end();
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pinMode(nano_tx, INPUT);
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}
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void turnPowerOff(uint32_t delay = 30000, bool _turn_hassio_power_off = false)
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@@ -289,7 +289,7 @@ void setup()
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pinMode(relay, OUTPUT);
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relayOn();
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display.begin(&Serial);
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display.begin(&nanoSerial);
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// display.setTiming(200);
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// display.setTiming(180);
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// display.setTiming(220); // works best so far
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+2
-2
@@ -77,5 +77,5 @@ pinout.
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| ROW_0 … ROW_4 | A3, A4, A2, A0, A1 |
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| ROW_RESET | D13 |
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| ROW_SET | A5 |
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| Serial RX | D0 (from ESP32 TX) |
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| Serial TX | D1 (to ESP32 RX, through a 5 V → 3.3 V voltage divider). Optional: needed for `READY`. Without it, the ESP waits the full 3 s timeout. |
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| Serial RX | D0 (from ESP32 GPIO 17, TX2) |
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| Serial TX | D1 (to ESP32 GPIO 16, RX2, through a 5 V → 3.3 V voltage divider). Optional: needed for `READY`. Without it, the ESP waits the full 3 s timeout. |
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