Mar 24, 2020
04:35 AM
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Mar 24, 2020
04:35 AM
Hello everyone,
I have an issue with the USB. I read via I2C a temperature sensor and send the value to the pc. The problem is the float value is wrong. I checked it with the calculator but the decimal places are zero every time.
I send both values MSB and LSB, temperature (float) and a test value (float) to my pc. The test value is correct but the temp value is wrong.
Why I receive 21.0000 and not 21.875 (calc: 1*16+(94/16))?
Here is my code:
BR David
I have an issue with the USB. I read via I2C a temperature sensor and send the value to the pc. The problem is the float value is wrong. I checked it with the calculator but the decimal places are zero every time.
I send both values MSB and LSB, temperature (float) and a test value (float) to my pc. The test value is correct but the temp value is wrong.
Why I receive 21.0000 and not 21.875 (calc: 1*16+(94/16))?
Here is my code:
#include
#include
#include
#include
#include
#define TEST_SUCCESS 1
#define TEST_FAILED 0
typedef enum MPU6050
{
//ADR = 0x68 << 1, //GY-521 or 0b11010000
//T_C = 0x42, // << 1,
//T_C = 0b1000001,
//GY_x = 0b0100010
GY_x = 0x44
} MPU6050_REGADDR_t;
typedef enum MPC9809
{
ADR = 0x18 << 1, //MPC9809
REG_CONF = 0x01 << 1,
SHUT_UP_DOWN = 0x0100 << 1
} TEMP_SENS;
char mb[200]; // MessageBuffer for sprintf()
void delay(uint32_t);
volatile uint8_t tx_completion_0 = 0, rx_completion_0 = 0;
int main(void)
{
uint32_t i2c_master_fifo_xfer_status = 0;
DAVE_STATUS_t status;
status = DAVE_Init();
USBD_VCOM_Connect();
while(!USBD_VCOM_IsEnumDone());
while(!cdc_event_flags.line_encoding_event_flag);
delay(0xffff);
if(status != DAVE_STATUS_SUCCESS)
{
while(true){}
}
while (true)
{
uint8_t i2c_data_x[1];
uint8_t i2c_temp = 0x00;
I2C_MASTER_Init(&I2C_MASTER_0);
I2C_MASTER_Transmit(&I2C_MASTER_0, true, ADR, &i2c_temp, 1, true);
while (tx_completion_0 == 0);
tx_completion_0 = 0;
i2c_temp = 0x05;
I2C_MASTER_Transmit(&I2C_MASTER_0, true, ADR, &i2c_temp, 1, false);
while (tx_completion_0 == 0);
tx_completion_0 = 0;
I2C_MASTER_Receive(&I2C_MASTER_0,true, ADR, i2c_data_x, 2, true, true);
while(rx_completion_0 == 0);
rx_completion_0 = 0;
if (!i2c_master_fifo_xfer_status)
{
i2c_master_fifo_xfer_status = TEST_SUCCESS;
}
else
{
i2c_master_fifo_xfer_status = TEST_FAILED;
}
float temp = 0;
i2c_data_x[0] = i2c_data_x[0] & 0x1f;
if ((i2c_data_x[0] & 0x10) == 0x10)
{
i2c_data_x[0] = i2c_data_x[1] & 0x0f;
temp = 256 - ((i2c_data_x[0]*16) + (i2c_data_x[1]/16));
}
else
{
temp = (i2c_data_x[0]*16) + (i2c_data_x[1]/16);
}
float test_val = 16.492;
sprintf(mb, "T1 = %d || T2 = %d || value: %f\n", i2c_data_x[0], i2c_data_x[1], test_val);
USBD_VCOM_SendString((int8_t*)mb);
CDC_Device_USBTask(&USBD_VCOM_cdc_interface);
sprintf(mb, "%f \n", temp);
USBD_VCOM_SendString((int8_t*)mb);
CDC_Device_USBTask(&USBD_VCOM_cdc_interface);
delay(0xffffff);
}
return 1;
}
void delay(uint32_t cnt)
{
volatile uint32_t count = cnt;
while (--count)
{
}
}
void EndOfTransmit(void)
{
tx_completion_0 = 1;
}
void EndOfReceive(void)
{
rx_completion_0 = 1;
}
BR David
- Tags:
- IFX
2 Replies
Mar 24, 2020
06:44 AM
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Mar 24, 2020
06:44 AM
Hallo there!
Not sitting in front of my IDE, so just replying from the top of my head,
change the lines : temp = (i2c_data_x[0]*16) + (i2c_data_x[1]/16);
to : temp = (i2c_data_x[0]*16.0) + (i2c_data_x[1]/16.0);
Your i2c_data_x is an integer and dividing by 16 will do integer division whereas dividing by 16.0 will force it to do floating point division
Not sitting in front of my IDE, so just replying from the top of my head,
change the lines : temp = (i2c_data_x[0]*16) + (i2c_data_x[1]/16);
to : temp = (i2c_data_x[0]*16.0) + (i2c_data_x[1]/16.0);
Your i2c_data_x is an integer and dividing by 16 will do integer division whereas dividing by 16.0 will force it to do floating point division
Mar 24, 2020
07:13 AM
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Mar 24, 2020
07:13 AM
oh yes, I forgot to try 16.0. Thank you for your answer. it works 🙂