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/**
* Flowerpot Device Firmware
*
* Copyright © 2021 Jesse Morgan <jesse@jesterpm.net>
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the “Software”),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#include <Arduino.h>
#include <ESP8266WiFi.h>
#include <ESP8266WiFiMulti.h>
#include <ESP8266HTTPClient.h>
#include <WiFiClient.h>
#include "Seeed_mbedtls.h"
#include "config.h"
// IO Pin Configuration
#define BATTERY_SWITCH D6
#define MEASURE_SWITCH D8
// Wifi
ESP8266WiFiMulti WiFiMulti;
// HMAC Context
mbedtls_md_context_t ctx;
const mbedtls_md_type_t MD_TYPE = MBEDTLS_MD_SHA256;
#define HMAC_SIZE_BYTES 32
const char* HEX_BYTE = "0123456789ABCDEF";
// The length of the secret key defined in config.h
#define SECRET_KEY_LEN sizeof(SECRET_KEY) - sizeof(SECRET_KEY[0])
// Generate an HMAC signature for a payload.
const char* generate_signature(const char* payload, size_t len) {
byte hmacResult[HMAC_SIZE_BYTES];
static char hexstring[2 * HMAC_SIZE_BYTES + 1];
// Generate the HMAC
mbedtls_md_hmac_starts(&ctx, (const unsigned char *) SECRET_KEY, SECRET_KEY_LEN);
mbedtls_md_hmac_update(&ctx, (const unsigned char *) payload, len);
mbedtls_md_hmac_finish(&ctx, hmacResult);
// Encode as a hex string
for (int i = 0; i < HMAC_SIZE_BYTES; i++) {
hexstring[2 * i] = HEX_BYTE[(hmacResult[i] >> 4) & 0x0F];
hexstring[2 * i + 1] = HEX_BYTE[hmacResult[i] & 0xF];
}
hexstring[2 * HMAC_SIZE_BYTES] = 0;
return hexstring;
}
// Read the ADC and return a value between 0 and 1.
float read_value(int pin) {
pinMode(A0, INPUT);
// Connect load to the ADC
digitalWrite(pin, HIGH);
// Give things a second to normalize
delay(100);
int raw;
// The ADC will return a value from 0 to 1024,
// corresponding to a voltage range between 0 and 1 volts.
raw = analogRead(A0);
// Disconnect load from the ADC
digitalWrite(pin, LOW);
return raw / 1024.0;
}
void setup() {
Serial.begin(115200);
Serial.println("\n\n");
// Initialize the output variables as outputs
pinMode(LED_BUILTIN, OUTPUT);
#ifdef HAS_BATTERY
pinMode(BATTERY_SWITCH, OUTPUT);
#endif
pinMode(MEASURE_SWITCH, OUTPUT);
// Set outputs to LOW
digitalWrite(LED_BUILTIN, LOW);
#ifdef HAS_BATTERY
digitalWrite(BATTERY_SWITCH, LOW);
#endif
digitalWrite(MEASURE_SWITCH, LOW);
for (uint8_t t = 4; t > 0; t--) {
Serial.printf("[SETUP] WAIT %d...\n", t);
Serial.flush();
delay(1000);
}
Serial.printf("Hello, my name is %x, you killed my father...\n", system_get_chip_id());
Serial.printf("Key len %d\n", SECRET_KEY_LEN);
WiFi.mode(WIFI_STA);
WiFiMulti.addAP("your_network", "your_password?");
// Prepare the HMAC context
mbedtls_md_init(&ctx);
mbedtls_md_setup(&ctx, mbedtls_md_info_from_type(MD_TYPE), 1);
}
void loop() {
// wait for WiFi connection
if ((WiFiMulti.run() == WL_CONNECTED)) {
#ifdef USE_TLS
WiFiClientSecure client;
client.setFingerprint(FINGERPRINT);
#else
WiFiClient client;
#endif
HTTPClient http;
Serial.print("[HTTP] begin...\n");
digitalWrite(LED_BUILTIN, LOW);
if (http.begin(client, ENDPOINT)) { // HTTP
http.addHeader("Content-Type", "application/x-www-form-urlencoded");
Serial.print("[HTTP] PUT...\n");
// start connection and send HTTP header
#ifdef HAS_BATTERY
// Get current battery state.
Serial.println("Reading battery...");
float battery_value = read_value(BATTERY_SWITCH);
#else
float battery_value = 1.0;
#endif
// Get the current resistance
Serial.println("Reading R...");
float value = read_value(MEASURE_SWITCH);
Serial.printf("Raw measure value = %f\n", value);
value = value * 1024.0 / 938.0;
Serial.printf("Calibrated measure value = %f\n", value);
float r = 320000.0 / value - 320000.0;
Serial.printf("R = %f\n", r);
// Payload
const size_t payload_length = 1024;
char payload[payload_length];
int len = snprintf(payload, payload_length,
"battery_value=%0.2f&device_id=%08x&value=%0.2f&signature=",
battery_value,
system_get_chip_id(),
r);
if (len + 65 <= payload_length) {
const char* signature = generate_signature(payload, len - 11);
strncpy(payload + len, signature, 65);
} else {
Serial.printf("Overflow! '%s'\n", payload);
}
Serial.printf("Putting payload '%s'\n", payload);
int httpCode = http.PUT(payload);
// httpCode will be negative on error
if (httpCode > 0) {
// HTTP header has been send and Server response header has been handled
Serial.printf("[HTTP] PUT... code: %d\n", httpCode);
// file found at server
if (httpCode == HTTP_CODE_OK || httpCode == HTTP_CODE_MOVED_PERMANENTLY) {
String payload = http.getString();
Serial.println(payload);
}
} else {
Serial.printf("[HTTP] PUT... failed, error: %s\n", http.errorToString(httpCode).c_str());
}
http.end();
} else {
Serial.printf("[HTTP} Unable to connect\n");
}
digitalWrite(LED_BUILTIN, HIGH);
Serial.printf("Nighty night.\n");
#ifdef HAS_BATTERY
ESP.deepSleep(3600 * 1000000);
#else
ESP.deepSleep(900 * 1000000);
#endif
}
}
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