Become a leader in the IoT community!

New DevHeads get a 320-point leaderboard boost when joining the DevHeads IoT Integration Community. In addition to learning and advising, active community leaders are rewarded with community recognition and free tech stuff. Start your Legendary Collaboration now!

Step 1 of 5

CREATE YOUR PROFILE *Required

OR
Step 2 of 5

WHAT BRINGS YOU TO DEVHEADS? *Choose 1 or more

Collaboration & Work šŸ¤
Learn & Grow šŸ“š
Contribute Experience & Expertise šŸ”§
Step 3 of 5

WHAT'S YOUR INTEREST OR EXPERTISE? *Choose 1 or more

Hardware & Design šŸ’”
Embedded Software šŸ’»
Edge Networking āš”
Step 4 of 5

Personalize your profile

Step 5 of 5

Read & agree to our COMMUNITY RULES

  1. We want this server to be a welcoming space! Treat everyone with respect. Absolutely no harassment, witch hunting, sexism, racism, or hate speech will be tolerated.
  2. If you see something against the rules or something that makes you feel unsafe, let staff know by messaging @admin in the "support-tickets" tab in the Live DevChat menu.
  3. No age-restricted, obscene or NSFW content. This includes text, images, or links featuring nudity, sex, hard violence, or other graphically disturbing content.
  4. No spam. This includes DMing fellow members.
  5. You must be over the age of 18 years old to participate in our community.
  6. Our community uses Answer Overflow to index content on the web. By posting in this channel your messages will be indexed on the worldwide web to help others find answers.
  7. You agree to our Terms of Service (https://www.devheads.io/terms-of-service/) and Privacy Policy (https://www.devheads.io/privacy-policy)
By clicking "Finish", you have read and agreed to the our Terms of Service and Privacy Policy.

Why is my BMP280 sensor value calculation incorrect on AtMega32?

Iā€™m working with the BMP280 sensor on an AtMega32 microcontroller, aiming to convert sensor data from raw readings to a human-readable format. Specifically, I need to read calibration values from the sensorā€™s registers and combine them to get meaningful numbers. Iā€™m able to read most of the calibration values correctly, but one particular value is being miscalculated. The process involves reading the LSB (Least Significant Byte) and MSB (Most Significant Byte) from the sensor, then combining these bytes into a single value. Below is my implementation:

uint8_t cmd[2] = {0xD0, 0};
uint8_t msb1 = 0;
uint8_t lsb1 = 0;
char str[32];

// Reading LSB
cmd[0] = 0x8E;
tw_master_transmit(0x76, cmd, 1, 0);
tw_master_receive(0x76, cmd, sizeof(cmd));
lsb1 = cmd[0];

// Reading MSB
cmd[0] = 0x8F;
tw_master_transmit(0x76, cmd, 1, 0);
tw_master_receive(0x76, cmd, sizeof(cmd));
msb1 = cmd[0];

// Print values
sprintf(str, "%d.%05urn", (int)lsb1, (int)((lsb1 - (int)lsb1) * 100000));
print_string(str);
sprintf(str, "%d.%05urn", (int)msb1, (int)((msb1 - (int)msb1) * 100000));
print_string(str);

// Combining LSB and MSB
uint16_t dig_p1 = (msb1 << 8) | lsb1;

// Print combined value
sprintf(str, "%d.%05urn", (int)dig_p1, (int)((dig_p1 - (int)dig_p1) * 100000));
print_string(str);

The value in `lsb1` and `msb1` are confirmed to be read correctly (verified with a different microcontroller), and the expected combined value should be 38406. However, my MCU is showing -27130. All other values are computed accurately. What could be causing this discrepancy?

CONTRIBUTE TO THIS THREAD

Browse other Product Reviews tagged

Leaderboard

RANKED BY XP

All time
  • 1.
    Avatar
    @Nayel115
    1620 XP
  • 2.
    Avatar
    @UcGee
    650 XP
  • 3.
    Avatar
    @melta101
    600 XP
  • 4.
    Avatar
    @lifegochi
    250 XP
  • 5.
    Avatar
    @Youuce
    180 XP
  • 6.
    Avatar
    @hemalchevli
    170 XP