|
There are two ways for the LPS22HB pressure sensor to determine whether the data is ready after starting the conversion. One is to read the STATUS (27h) register to determine whether T_DA and P_DA are 1 This is a passive method, which requires the microcontroller to continuously read and judge, which wastes processor resources and will also have a certain delay Another method is to use the interrupt pin of the sensor. After the data is good, the sensor notifies the processor to read and process the data by changing the level of the interrupt pin In this way, the processor can handle other things before triggering the interrupt, or enter the power-down state, which can save processor resources and reduce power consumption LPS22HB has an INT_DRDY (Interrupt or Data Ready) pin, on PIN7 of the chip, is used to notify the processor to handle the corresponding interrupt , including the DRDY interrupt function 336896[/attach] BlueCoinThe evaluation board connects this pin to the PB3 pin of the STM32F446 336897[/attach] To use the Interrupt or Data Ready function, you need to configure the DRDY bit of the sensor's CTRL_REG3 (12h) register to 1 and enable the DRDY function. The following measures the maximum Pressure output data rate of LPS22HB by interrupting the DRDY state of the sensor received by the PB3 pin of the STM32F446. The data sheet shows that LPS22HB supports 1Hz, 10Hz, 25 Hz, 50 Hz and 75 Hz several rates Add a flag drdy_flag Configure the interrupt function of PB3 of STM32F446 After triggering the rising edge interrupt, change drdy_flag to 1 Add a function enable_drdy to enable DRDY, and set the DRDY bit of the CTRL_REG3 (12h) register to 1 in the function Here just directly set CTRL_REG3 (12h) register, which is equivalent to all the data of CTRL_REG3 (12h) except DRDY being 0 If you need to configure other bits of CTRL_REG3 (12h), you usually need to read the data of CTRL_REG3 (12h) before writing, then modify the DRDY bit, and then write the data back This ensures that other configured bits will not be modified. This method is used in the official driver 336902[/attach] Continued from the previous post Use the one_shot method to read data and see how long it takes for LPS22HB to convert data once The original data is readSTATUS (27h) The code for judging the data readiness of the register is changed to judging the drdy_flag flag. Before enabling ONE_SHOT, set drdy_flag to 0. Before reading the pressure and temperature, wait for drdy_flag to be set to 1 by the rising edge interrupt of the PB3 pin. 336903 The BlueCoinevaluation board is highly integrated, so it is impossible to use an oscilloscope to measure the line from PIN7 of LPS22HB to PB3 pin of STM32F446 You can modify the state of a GPIO in the HAL_GPIO_EXTI_Callback interrupt, and then use an oscilloscope to measure the GPIO to determine the DRDY trigger timing Here we use a pin PD7 in BlueCoin to control the LED. When DRDY is triggered, change PD7 to 1 Set PD7 to 0 before executing ONE_SHOT The one_shot function is executed in a loop, and PD7 is measured with an oscilloscope to obtain the following waveform The time from setting PD7 to 0 to PD7 being modified to 1 by the DRDY interrupt is 13.2ms, and the corresponding rate is 75.8Hz Because an I2C communication is executed after PD7 is set to 0 to enable the ONE_SHOT interrupt, the actual conversion time should be less than 13.2ms which is basically the same as the maximum ODR of 75Hz in the data sheet 2ms is basically the same as the maximum ODR of 75Hz in the data sheet336906[/attach] 2ms is basically the same as the maximum ODR of 75Hz in the data sheet336906[/attach]
| 
提升卡
变色卡
千斤顶
京公网安备 11010802033920号
