FXOS8700CQ i2c functionality failure on Beaglebone

priyanks — Tue, 03 Feb 2026 22:50:52 GMT

Hi,

Forgive my lack of expert knowledge on this subject. I am working on interfacing the FRDM-STBC-AGM01 (FXOS8700CQ and FXAS21002). Due to this setup type with beaglebone I am unable to get any of the toolbars to work. I am trying to get started by reading the WHO_AM_I and writing to CTRL_REG1 on the board using i2c. The program only prints zero value for both cases. Can an expert suggest what I am doing wrong?

int main(void) { char rxBuffer[32]; // receive buffer char txBuffer[32]; // transmit buffer int gyroAddress = 0x20; // gyro device address int xlAddress = 0x1E; // accelerometer device address int tenBitAddress = 0; // is the device's address 10-bit? Usually not. int opResult = 0; // for error checking of operations // Create a file descriptor for the I2C bus int i2cHandle = open("/dev/i2c-1", O_RDWR); // Tell the I2C peripheral that the device address is (or isn't) a 10-bit opResult = ioctl(i2cHandle, I2C_TENBIT, tenBitAddress); // Tell the I2C peripheral what the address of the device is opResult = ioctl(i2cHandle, I2C_SLAVE, gyroAddress); // Clear our buffers memset(rxBuffer, 0, sizeof(rxBuffer)); memset(txBuffer, 0, sizeof(txBuffer)); //We're going to ask the gyro to read back its "WHO_AM_I" txBuffer[0] = 0x0C; // This is the address we want to read from. opResult = write(i2cHandle, txBuffer, 1); if (opResult != 1) printf("No ACK bit!\n"); opResult = read(i2cHandle, rxBuffer, 1); printf("Part ID: %d\n", (int)rxBuffer[0]); // we need to change the slave address! opResult = ioctl(i2cHandle, I2C_SLAVE, xlAddress); txBuffer[0] = 0x0D; // This is the address to read from. opResult = write(i2cHandle, txBuffer, 1); if (opResult != 1) printf("No ACK bit!\n"); opResult = read(i2cHandle, rxBuffer, 1); printf("Part ID: %d\n", (int)rxBuffer[0]); }

I can read values from the sensor using i2cget/dump commands. Program seems simple but still does not function. Any hints?

Thank you.

Re: FXOS8700CQ i2c functionality failure on Beaglebone

michaelestanley — Fri, 12 Jun 2015 16:29:44 GMT

Priyank,

I've moved your question to the general Sensors community, as I think we're more likely to get you a good answer here. The sensorfusion team has no experience with the BeagleBoard, so can't be much help.

Mike

SensorsのトピックFXOS8700CQ i2c functionality failure on Beaglebone

FXOS8700CQ i2c functionality failure on Beaglebone

Re: FXOS8700CQ i2c functionality failure on Beaglebone