Display BTCUSD chart on e-ink display

btcusdDisplay.cpp

#include <Arduino.h>
#include <WiFi.h>
#include <HTTPClient.h>
#include <ArduinoJson.h>
#include <vector>

#include "epd_driver.h"
#include "firasans.h"

uint8_t* eink_framebuffer;

const char* ssid = "";
const char* password = "";

int eink_cursor[2] = {0, 50};

String bitAPIurl = "http://api.coindesk.com/v1/bpi/historical/close.json";
HTTPClient http;
DynamicJsonDocument bpiJson(1536);
std::vector<double> bpiPriceList;

void setup() {
    Serial.begin(115200); 
    epd_init(); epd_poweron(); epd_clear();

    eink_framebuffer = (uint8_t *)heap_caps_malloc(EPD_WIDTH * EPD_HEIGHT / 2, MALLOC_CAP_SPIRAM);
    memset(eink_framebuffer, 0xff, EPD_WIDTH * EPD_HEIGHT / 2);

    WiFi.begin(ssid, password);
    write_string((GFXfont *)&FiraSans, "Connecting WiFi", &eink_cursor[0], &eink_cursor[1], NULL);

    int retries = 0;
    while (WiFi.status() != WL_CONNECTED)
    {
        if(retries++ > 10)
        {
            esp_restart();
        }
        delay(500);
        eink_cursor[1] = 50;
        write_string((GFXfont *)&FiraSans, ".", &eink_cursor[0], &eink_cursor[1], NULL);
    }
    eink_cursor[0] = 0;
    writeln((GFXfont *)&FiraSans, "Connected! <3", &eink_cursor[0], &eink_cursor[1], NULL);
    delay(300);
    Serial.println("Connected.");

    eink_cursor[0] = 0; eink_cursor[1] += 50;
    writeln((GFXfont *)&FiraSans, "Getting historical price...", &eink_cursor[0], &eink_cursor[1], NULL);
    http.begin(bitAPIurl);

    int respCode = http.GET();
    if(respCode == 0) 
    {
        Serial.print("Http error :");
        Serial.println(respCode);
        eink_cursor[0] = 0;
        eink_cursor[1] += 50;
        writeln((GFXfont *)&FiraSans, "Http internal error", &eink_cursor[0], &eink_cursor[1], NULL);
    } else if (respCode != 200)
    {
        char errorString[30];
        sprintf(errorString, "Http Error : %d", respCode);
        eink_cursor[0] = 0; eink_cursor[1] += 50;
        writeln((GFXfont *)&FiraSans, errorString, &eink_cursor[0], &eink_cursor[1], NULL);
    }
    
    String respString = http.getString();
    Serial.println(respCode);
    Serial.println(respString.length());
    deserializeJson(bpiJson, respString);
    JsonObject bpiObject = bpiJson.as<JsonObject>();
    http.end();
    for(auto bpiPair: bpiObject["bpi"].as<JsonObject>()) {
        bpiPriceList.push_back(bpiPair.value().as<double>());
    }

    double maxPrice = *std::max_element(std::begin(bpiPriceList), std::end(bpiPriceList));
    double minPrice = *std::min_element(std::begin(bpiPriceList), std::end(bpiPriceList));
    Serial.printf("%f, %f", maxPrice, minPrice);
    for(int i = 0; i < bpiPriceList.size() - 1; i++) {
        double beforeHeight = EPD_HEIGHT - (bpiPriceList[i] - minPrice) / (maxPrice - minPrice) * EPD_HEIGHT;
        double afterHeight = EPD_HEIGHT - (bpiPriceList[i + 1] - minPrice) / (maxPrice - minPrice) * EPD_HEIGHT;
        epd_draw_line(i * EPD_WIDTH / (bpiPriceList.size() - 1), (int)beforeHeight, (i + 1) * EPD_WIDTH / (bpiPriceList.size() - 1), (int)afterHeight, 0, eink_framebuffer);
    }

    epd_clear();
    epd_draw_grayscale_image(epd_full_screen(), eink_framebuffer);
    epd_poweroff();
}

void loop() {
}