Platform: atmelavr
==============================================================
ID         MCU         Frequency    Flash    RAM    Name
---------  ----------  -----------  -------  -----  ---------
seeeduino  ATMEGA328P  16MHz        31.50KB  2KB    Seeeduino

Platform: atmelsam
====================================================================
ID                MCU        Frequency Flash RAM  Name
----------------- ---------- --------- ----- ---- ------------------
seeed_femto       SAMD21G18A 48MHz     256KB 32KB Seeeduino Femto M0
seeeduino_lorawan SAMD21G18A 48MHz     256KB 32KB Seeeduino LoRaWAN
seeed_xiao        SAMD21G18A 48MHz     256KB 32KB Seeeduino XIAO
seeed_zero        SAMD21G18A 48MHz     256KB 32KB Seeeduino Zero

#define TX_PIN 11
#define RX_PIN 12

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(TX_PIN,      OUTPUT);
  pinMode(RX_PIN,      OUTPUT);
}

void loop() {
  digitalWrite(LED_BUILTIN, LOW);
  delay(500);
  digitalWrite(LED_BUILTIN, HIGH);
  delay(500);
  digitalWrite(TX_PIN, LOW);
  delay(500);
  digitalWrite(TX_PIN, HIGH);
  delay(500);
  digitalWrite(RX_PIN, LOW);
  delay(500);
  digitalWrite(RX_PIN, HIGH);
  delay(500);
}

$ platformio platform update

Platform Atmel AVR
--------
Updating atmelavr                        @ 2.2.0          [Up-to-date]
Updating toolchain-atmelavr              @ 1.50400.190710 [Up-to-date]
Updating framework-arduino-avr-minicore  @ 2.0.5          [Up-to-date]
Updating framework-arduino-avr           @ 5.0.0          [Up-to-date]
Updating tool-avrdude                    @ 1.60300.200527 [Up-to-date]

Platform Atmel SAM
--------
Updating atmelsam                        @ 4.5.1          [Up-to-date]
Updating tool-bossac                     @ 1.10700.190624 [Up-to-date]
Updating framework-arduino-samd-seeed    @ 1.7.6          [Up-to-date]
Updating framework-cmsis-atmel           @ 1.2.0          [Up-to-date]
Updating tool-avrdude                    @ 1.60300.200527 [Up-to-date]
Updating toolchain-gccarmnoneeabi        @ 1.70201.0      [Up-to-date]
Updating framework-cmsis                 @ 1.40500.0      [Up-to-date]

Platform Atmel SAM
--------
Updating atmelsam                        @ 3.6.1          [Detached]
Updating tool-avrdude                    @ 1.60300.200527 [Up-to-date]
Updating tool-bossac                     @ 1.10700.190624 [Up-to-date]

Platform Espressif 32
--------
Updating espressif32                     @ 1.12.4         [Up-to-date]
Updating framework-arduinoespressif32    @ 3.10004.200129 [Up-to-date]
Updating tool-esptoolpy                  @ 1.20600.0      [Up-to-date]

$ vi ~/.platformio/platforms/atmelsam/platform.json
   "toolchain-gccarmnoneeabi": {
      "type": "toolchain",
      "version": "~1.70201.0"
           ↓変更
      "version": ">=1.40803.0,<1.40805.0"
    },

$ vi serial.ino
void setup() {
  Serial.begin(9600);
}
 
void loop() {
  if (Serial.available() > 0) {
    char c = Serial.read();
    Serial.println((char)c);
  }
}

$ vi src/adafruit_aht_test.ino
#include <Adafruit_AHTX0.h>

Adafruit_AHTX0 aht;

void setup() {
  Serial.begin(115200);
  if (!aht.begin()) {
    Serial.println("Could not find AHT? Check wiring");
    while (1) delay(10);
  }
}

void loop() {
  sensors_event_t humidity, temp;
  aht.getEvent(&humidity, &temp);
  Serial.print(temp.temperature);
  Serial.print("℃ ");
  Serial.print(humidity.relative_humidity);
  Serial.println("％");
  delay(500);
}

$ vi platformio.ini
lib_deps =
  6214

$ vi platformio.ini
lib_deps =
  6214
  31

#include <Adafruit_AHTX0.h>
#include <Adafruit_GFX.h>
#include <Adafruit_ST7735.h>
#include <SPI.h>

#define TFT_CS    1
#define TFT_RST   2
#define TFT_DC    3
#define TFT_SCLK  8
#define TFT_MOSI 10

#define BLACK   ST7735_WHITE
#define CYAN    ST7735_BLUE
#define ORANGE  ST7735_ORANGE

Adafruit_AHTX0  aht;
Adafruit_ST7735 tft = Adafruit_ST7735(TFT_CS, TFT_DC, TFT_MOSI,
TFT_SCLK, TFT_RST);

void setup(void) {

  if (! aht.begin()) {
    Serial.println("Could not find AHT? Check wiring");
    while (1) delay(10);
  }
  tft.initR(INITR_MINI160x80);

  tft.setTextWrap(false);
  tft.setRotation(3);
}

void loop() {

  sensors_event_t humidity, temp;
  aht.getEvent(&humidity, &temp);

  tft.fillScreen(BLACK);
  tft.setCursor(5, 30);
  tft.setTextSize(2);

  tft.setTextColor(ORANGE);
  tft.print(temp.temperature);
  tft.print("C ");

  tft.setTextColor(CYAN);
  tft.print(humidity.relative_humidity);
  tft.println("%");

  delay(1000);
}

$ vi platformio.ini
lib_deps =
  6214
  31
  13
  12