Shows available RAM

exercises/15_RAM/README.md

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+# Exercise 15: RAM
+
+This exercise shows available RAM on the console and on the OLED display on a T-Beam Supreme.
+
+Behavior:
+- Reports heap statistics every second over serial.
+- Shows live heap status on the OLED display.
+- Designed as the first step toward volatile /tmp RAM-backed storage.
+
+Build and upload:
+
+```bash
+cd /usr/local/src/microreticulum/microReticulumTbeam/exercises/15_RAM
+pio run -e amy -t upload
+pio device monitor -b 115200
+```

exercises/15_RAM/platformio.ini

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+; 20260403 ChatGPT
+; Exercise 15_RAM
+
+[platformio]
+default_envs = amy
+
+[env]
+platform = espressif32
+framework = arduino
+board = esp32-s3-devkitc-1
+monitor_speed = 115200
+extra_scripts = pre:scripts/set_build_epoch.py
+lib_deps =
+  Wire
+  olikraus/U8g2@^2.36.4
+
+build_flags =
+  -I ../../shared/boards
+  -I ../../external/microReticulum_Firmware
+  -D BOARD_MODEL=BOARD_TBEAM_S_V1
+  -D OLED_SDA=17
+  -D OLED_SCL=18
+  -D OLED_ADDR=0x3C
+  -D ARDUINO_USB_MODE=1
+  -D ARDUINO_USB_CDC_ON_BOOT=1
+
+[env:amy]
+extends = env
+build_flags =
+  ${env.build_flags}
+  -D NODE_LABEL=\"AMY\"
+
+[env:bob]
+extends = env
+build_flags =
+  ${env.build_flags}
+  -D NODE_LABEL=\"BOB\"
+
+[env:cy]
+extends = env
+build_flags =
+  ${env.build_flags}
+  -D NODE_LABEL=\"CY\"
+
+[env:dan]
+extends = env
+build_flags =
+  ${env.build_flags}
+  -D NODE_LABEL=\"DAN\"
+
+[env:ed]
+extends = env
+build_flags =
+  ${env.build_flags}
+  -D NODE_LABEL=\"ED\"

exercises/15_RAM/scripts/set_build_epoch.py

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+import time
+Import("env")
+
+epoch = int(time.time())
+utc_tag = time.strftime("%Y%m%d_%H%M%S_z", time.gmtime(epoch))
+
+env.Append(
+    CPPDEFINES=[
+        ("FW_BUILD_EPOCH", str(epoch)),
+        ("FW_BUILD_UTC", '\\"%s\\"' % utc_tag),
+    ]
+)

exercises/15_RAM/src/main.cpp

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+// 20260403 ChatGPT
+// Exercise 15_RAM
+
+#include <Arduino.h>
+#include <Wire.h>
+#include <U8g2lib.h>
+
+#ifndef NODE_LABEL
+#define NODE_LABEL "RAM"
+#endif
+
+#ifndef OLED_SDA
+#define OLED_SDA 17
+#endif
+#ifndef OLED_SCL
+#define OLED_SCL 18
+#endif
+#ifndef OLED_ADDR
+#define OLED_ADDR 0x3C
+#endif
+
+static U8G2_SH1106_128X64_NONAME_F_HW_I2C g_oled(U8G2_R0, U8X8_PIN_NONE);
+
+static void oledShowLines(const char *l1,
+                          const char *l2 = nullptr,
+                          const char *l3 = nullptr,
+                          const char *l4 = nullptr,
+                          const char *l5 = nullptr)
+{
+  g_oled.clearBuffer();
+  g_oled.setFont(u8g2_font_5x8_tf);
+  if (l1) g_oled.drawUTF8(0, 12, l1);
+  if (l2) g_oled.drawUTF8(0, 24, l2);
+  if (l3) g_oled.drawUTF8(0, 36, l3);
+  if (l4) g_oled.drawUTF8(0, 48, l4);
+  if (l5) g_oled.drawUTF8(0, 60, l5);
+  g_oled.sendBuffer();
+}
+
+static size_t getAvailableRamBytes()
+{
+  return ESP.getFreeHeap();
+}
+
+static void printRamStatus()
+{
+  const size_t freeBytes = getAvailableRamBytes();
+  const size_t totalBytes = ESP.getHeapSize();
+  const size_t maxAlloc = ESP.getMaxAllocHeap();
+
+  Serial.printf("RAM  total=%u free=%u maxAlloc=%u\r\n", (unsigned)totalBytes, (unsigned)freeBytes, (unsigned)maxAlloc);
+
+  char line1[32];
+  char line2[32];
+  char line3[32];
+
+  snprintf(line1, sizeof(line1), "Exercise 15 RAM");
+  snprintf(line2, sizeof(line2), "Node: %s", NODE_LABEL);
+  snprintf(line3, sizeof(line3), "Free: %u KB", (unsigned)(freeBytes / 1024U));
+  char line4[32];
+  snprintf(line4, sizeof(line4), "Total: %u KB", (unsigned)(totalBytes / 1024U));
+  char line5[32];
+  snprintf(line5, sizeof(line5), "Max alloc: %u KB", (unsigned)(maxAlloc / 1024U));
+
+  oledShowLines(line1, line2, line3, line4, line5);
+}
+
+void setup()
+{
+  Serial.begin(115200);
+  delay(800);
+  Serial.println("Exercise 15_RAM boot");
+
+  Wire.begin(OLED_SDA, OLED_SCL);
+  g_oled.setI2CAddress(OLED_ADDR << 1);
+  g_oled.begin();
+  oledShowLines("Exercise 15_RAM", "Node: " NODE_LABEL, "Booting...");
+
+  delay(1000);
+}
+
+void loop()
+{
+  static uint32_t lastMs = 0;
+  const uint32_t now = millis();
+  if (now - lastMs < 1000) {
+    delay(10);
+    return;
+  }
+  lastMs = now;
+
+  printRamStatus();
+}