ccs811.tc

CCS811 Digital Air Quality Sensor (eCO2 + TVOC)

Source on GitHub

// CCS811 Digital Air Quality Sensor (eCO2 + TVOC)
// I2C address: 0x5A (default) or 0x5B (ADDR pin high)
// HW_ID: 0x81
//
// Reports: eCO2 (400-8192 ppm), TVOC (0-1187 ppb)
// Measurement mode 1: 1-second interval
// Needs ~20 min warm-up for stable readings

#define CCS_ADDR1 0x5A
#define CCS_ADDR2 0x5B
#define CCS_HW_ID 0x81

// registers
#define CCS_STATUS   0x00
#define CCS_MEAS     0x01
#define CCS_ALG_DATA 0x02
#define CCS_ENV_DATA 0x05
#define CCS_HW_ID_REG 0x20
#define CCS_ERR_REG  0xE0
#define CCS_APP_START 0xF4
#define CCS_SW_RESET 0xFF

int ccs_addr = 0;
int ccs_bus = 0;
int ccs_ok = 0;
int ccs_eco2 = 0;
int ccs_tvoc = 0;
int ccs_err = 0;
char ccs_name[16];
char ccs_buf[16];
char ccs_lbl[32];

int ccs_scan() {
    int bus = 0;
    while (bus < 2) {
        int addr = CCS_ADDR1;
        while (addr <= CCS_ADDR2) {
            if (i2cSetDevice(addr, bus)) {
                int id = i2cRead8(addr, CCS_HW_ID_REG, bus);
                if (id == CCS_HW_ID) {
                    ccs_addr = addr;
                    ccs_bus = bus;
                    i2cSetActiveFound(ccs_addr, "CCS811", ccs_bus);
                    return 1;
                }
            }
            addr = addr + 1;
        }
        bus = bus + 1;
    }
    return 0;
}

int ccs_init() {
    // read status — check APP_VALID (bit 4)
    int status = i2cRead8(ccs_addr, CCS_STATUS, ccs_bus);
    if ((status & 0x10) == 0) {
        return 0;  // no valid app firmware
    }

    // if in boot mode (FW_MODE bit 7 = 0), send APP_START
    if ((status & 0x80) == 0) {
        i2cWrite0(ccs_addr, CCS_APP_START, ccs_bus);
        delay(100);
        // verify transition
        status = i2cRead8(ccs_addr, CCS_STATUS, ccs_bus);
        if ((status & 0x80) == 0) {
            return 0;  // failed to enter app mode
        }
    }

    // set measurement mode 1 (1-second interval), no interrupts
    i2cWrite8(ccs_addr, CCS_MEAS, 0x10, ccs_bus);
    return 1;
}

void EverySecond() {
    if (!ccs_ok) return;

    // check status: DATA_READY (bit 3)
    int status = i2cRead8(ccs_addr, CCS_STATUS, ccs_bus);
    if ((status & 0x04) != 0) {
        // error flag set
        ccs_err = i2cRead8(ccs_addr, CCS_ERR_REG, ccs_bus);
    }
    if ((status & 0x08) == 0) {
        return;  // data not ready
    }

    // read ALG_RESULT_DATA: 8 bytes from register 0x02
    // [eco2_hi, eco2_lo, tvoc_hi, tvoc_lo, status, error, raw_hi, raw_lo]
    int ret = i2cRead(ccs_addr, CCS_ALG_DATA, ccs_buf, 8, ccs_bus);
    if (ret) {
        ccs_eco2 = ((ccs_buf[0] & 0xFF) << 8) | (ccs_buf[1] & 0xFF);
        ccs_tvoc = ((ccs_buf[2] & 0xFF) << 8) | (ccs_buf[3] & 0xFF);
    }
}

void ccs_web_label(int idx) {
    char vt[48];
    LGetString(idx, ccs_lbl);
    strcpy(vt, "{s}");
    strcat(vt, ccs_name);
    strcat(vt, " ");
    strcat(vt, ccs_lbl);
    strcat(vt, "{m}");
    webSend(vt);
}

void WebCall() {
    char vt[32];
    if (ccs_ok) {
        // eCO2
        ccs_web_label(5);  // 5 = eCO2
        sprintf(vt, "%d ppm{e}", ccs_eco2);
        webSend(vt);
        // TVOC
        ccs_web_label(6);  // 6 = TVOC
        sprintf(vt, "%d ppb{e}", ccs_tvoc);
        webSend(vt);
    } else {
        webSend("{s}CCS811{m}not found{e}");
    }
}

void JsonCall() {
    if (!ccs_ok) return;
    char buf[64];
    strcpy(buf, ",\"");
    strcat(buf, ccs_name);
    strcat(buf, "\":{");
    responseAppend(buf);
    sprintf(buf, "\"eCO2\":%d", ccs_eco2);
    responseAppend(buf);
    sprintf(buf, ",\"TVOC\":%d}", ccs_tvoc);
    responseAppend(buf);
}

void OnExit() {
    if (ccs_addr) {
        // set mode 0 (idle) before releasing
        i2cWrite8(ccs_addr, CCS_MEAS, 0x00, ccs_bus);
        I2cResetActive(ccs_addr, ccs_bus);
        ccs_addr = 0;
    }
}

int main() {
    delay(10000);

    if (!ccs_scan()) return 0;

    // build name with address
    if (ccs_addr == CCS_ADDR1) {
        strcpy(ccs_name, "CCS811");
    } else {
        strcpy(ccs_name, "CCS811b");
    }

    if (!ccs_init()) {
        char dt[48];
        sprintf(dt, "CCS811 init failed (addr 0x%x)", ccs_addr);
        addLog(dt);
        return 0;
    }

    return 0;
}