Add SCD30 test

rp2040/.editorconfig

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+root = true
+
+[*]
+end_of_line = lf
+insert_final_newline = true
+charset = utf-8
+trim_trailing_whitespace = true
+
+[*.{c,h}]
+indent_style = space
+indent_size = 2
+
+[CMakeLists.txt,*.cmake]
+indent_style = space
+indent_size = 2

rp2040/.gitignore

@@ -0,0 +1,3 @@
+build/
+.cache/
+compile_commands.json

rp2040/scd30/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.12)
+
+include($ENV{PICO_SDK_PATH}/pico_sdk_init.cmake)
+set(CMAKE_C_STANDARD 11)
+
+project(scd30)
+pico_sdk_init()
+
+add_executable(scd30
+        scd30.c
+        )
+target_link_libraries(scd30 pico_stdlib hardware_i2c)
+pico_enable_stdio_usb(scd30 1)
+pico_add_extra_outputs(scd30)

rp2040/scd30/scd30.c

@@ -0,0 +1,108 @@
+#include <math.h>
+#include <stdio.h>
+
+#include "hardware/i2c.h"
+#include "pico/stdlib.h"
+
+struct scd30_result {
+  float temp_c;
+  float relative_humidity;
+};
+
+static struct i2c_inst *i2c = i2c1;
+const static uint32_t sda_pin = 2;
+const static uint32_t scl_pin = 3;
+const static uint8_t addr = 0x44;
+const static uint8_t crc8_table[] = {
+    0,   49,  98,  83,  196, 245, 166, 151, 185, 136, 219, 234, 125, 76,  31,
+    46,  67,  114, 33,  16,  135, 182, 229, 212, 250, 203, 152, 169, 62,  15,
+    92,  109, 134, 183, 228, 213, 66,  115, 32,  17,  63,  14,  93,  108, 251,
+    202, 153, 168, 197, 244, 167, 150, 1,   48,  99,  82,  124, 77,  30,  47,
+    184, 137, 218, 235, 61,  12,  95,  110, 249, 200, 155, 170, 132, 181, 230,
+    215, 64,  113, 34,  19,  126, 79,  28,  45,  186, 139, 216, 233, 199, 246,
+    165, 148, 3,   50,  97,  80,  187, 138, 217, 232, 127, 78,  29,  44,  2,
+    51,  96,  81,  198, 247, 164, 149, 248, 201, 154, 171, 60,  13,  94,  111,
+    65,  112, 35,  18,  133, 180, 231, 214, 122, 75,  24,  41,  190, 143, 220,
+    237, 195, 242, 161, 144, 7,   54,  101, 84,  57,  8,   91,  106, 253, 204,
+    159, 174, 128, 177, 226, 211, 68,  117, 38,  23,  252, 205, 158, 175, 56,
+    9,   90,  107, 69,  116, 39,  22,  129, 176, 227, 210, 191, 142, 221, 236,
+    123, 74,  25,  40,  6,   55,  100, 85,  194, 243, 160, 145, 71,  118, 37,
+    20,  131, 178, 225, 208, 254, 207, 156, 173, 58,  11,  88,  105, 4,   53,
+    102, 87,  192, 241, 162, 147, 189, 140, 223, 238, 121, 72,  27,  42,  193,
+    240, 163, 146, 5,   52,  103, 86,  120, 73,  26,  43,  188, 141, 222, 239,
+    130, 179, 224, 209, 70,  119, 36,  21,  59,  10,  89,  104, 255, 206, 157,
+    172};
+
+static uint8_t crc8(uint8_t msb, uint8_t lsb) {
+  return crc8_table[lsb ^ crc8_table[msb ^ 0xff]];
+}
+
+static void scd30_reset_all() {
+  // Generall call recet
+  uint8_t cmd[] = {0x06};
+  i2c_write_blocking(i2c, 0x00, cmd, sizeof(cmd), false);
+  // Datasheet says max hard reset time is 1ms, soft reset is 1.5ms
+  sleep_ms(2);
+}
+
+static uint16_t scd30_get_firmware_version() {
+  uint8_t cmd[] = {0xd1, 0x00};
+  i2c_write_blocking(i2c, addr, cmd, sizeof(cmd), true);
+  uint8_t resp[3];
+  i2c_read_blocking(i2c, addr, resp, sizeof(resp), false);
+  if (crc8(resp[0], resp[1]) != resp[2])
+    return 0xffff;
+  return (uint16_t)resp[0] << 8 | resp[1];
+}
+
+static void scd30_start_capture() {
+  // High repeatability, 1 sample per second
+  uint8_t cmd[] = {0x21, 0x30};
+  i2c_write_blocking(i2c, addr, cmd, sizeof(cmd), false);
+};
+
+static struct scd30_result scd30_fetch_data() {
+  uint8_t cmd[] = {0xe0, 0x00};
+  i2c_write_blocking(i2c, addr, cmd, sizeof(cmd), true);
+  uint8_t resp[6];
+  i2c_read_blocking(i2c, addr, resp, sizeof(resp), false);
+
+  float temp_c, relative_humidity;
+  if (crc8(resp[0], resp[1]) == resp[2])
+    temp_c = -45 + 175 * (float)(resp[0] << 8 | resp[1]) / 0xffff;
+  else
+    temp_c = NAN;
+
+  if (crc8(resp[3], resp[4]) == resp[5])
+    relative_humidity = 100 * (float)(resp[3] << 8 | resp[4]) / 0xffff;
+  else
+    relative_humidity = NAN;
+
+  struct scd30_result result = {.temp_c = temp_c,
+                                .relative_humidity = relative_humidity};
+  return result;
+}
+
+int main() {
+  stdio_init_all();
+
+  i2c_init(i2c, 100 * 1000);
+  gpio_set_function(sda_pin, GPIO_FUNC_I2C);
+  gpio_set_function(scl_pin, GPIO_FUNC_I2C);
+  gpio_pull_up(sda_pin);
+  gpio_pull_up(scl_pin);
+
+  sleep_ms(2000);
+
+  scd30_reset_all();
+
+  scd30_start_capture();
+
+  while (true) {
+    sleep_ms(1000);
+    struct scd30_result result = scd30_fetch_data();
+    printf("{\"temperature\": %f, \"humidity\": %f}\n", result.temp_c,
+           result.relative_humidity);
+  }
+  return 0;
+}

rp2040/shell.nix

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+with import <nixpkgs> { };
+let
+  sdk_src = fetchFromGitHub {
+    fetchSubmodules = true;
+    owner = "raspberrypi";
+    repo = "pico-sdk";
+    rev = "1.3.1";
+    sha256 = "sha256-Xf8QSQIe7XCMunljioC5/MhXcuTmyN7J6pPQFM3ico8=";
+  };
+in
+mkShell rec {
+  name = "pico-env";
+
+  nativeBuildInputs = [ pkgconfig ];
+
+  buildInputs = [
+    gnumake
+    cmake
+    ninja
+    python3
+    gcc
+    libusb
+    openocd
+    picotool
+    gcc-arm-embedded
+  ];
+
+  PICO_SDK_PATH = sdk_src;
+}