The driver for BMA423 Triaxial Acceleration Sensor

The MicroPython layer in bma423 from https://github.com/OPHoperHPO/lilygo-ttgo-twatch-2020-micropython was not working because it uses deprecated calls to I2C in MicroPython.

However, I found that Daniel Thomson has also written a MicroPython interface to the BMA423 API from Bosch SensorTec, which was easier to adapt to the t-watch.

https://github.com/daniel-thompson/bma42x-upy

I had to make only a few modifications: Daniel uses a BMA421 while the t-watch uses a BMA423. I therefore had to replace all occurrences of "bma421" in bma42x.c by "bma423". In addition the t-watch uses the secondary I2C address 0x19 for the chip (the primary address is 0x18) and I therefore had to replace ic2_addr in the device descriptor to BMA4_I2C_ADDR_SECONDARY.

Daniel also supplies a few example programs, which are essentially ports of the Bosch examples ported from C to MicroPython

The BMA42X driver provides the following methods:

• BMA42X(i2c): create a BMA42X object. The i2c parameter must be a initialized SoftI2C object
• debug(on_off): switch debugging on / off
• feature_enable(feature,on_off): feature: the feature to be enabled or disabled, on_off to switch the feature on or off. The features are listed below.
• get_offset_comp(): Gets the status of the accel offset compensation
• get_temperature(unit): gets the temperature in the requested units. Possible units: see below
• init (called when the object is created)
• map_interrupt(int_line, interrupt_types): Map the interrupt to either pin1 or pin2
• read_accel_xyz(): read the accel data for x,y,z from the sensor. The data are returned as a tuple (x,y,z)
• read_int_status(): reads the hardware interrupt status from the sensor
• set accel_config(accel_config): set the acceleration sensor config. See the accelerometer.py example in order to understand how to do this.
• reset_step_counter(): reset the step counter
• set accel_enable(on_off): enables or disables the accel in the sensor
• set_any_mot_config(any_mot_config): set the configuration for any motion interrupts. See example motion_interrupt.py in order to understand how to do this.
• set_no_mot_config(no_mot_config): set the configuration for no motion interrupts. See example motion_interrupt.py in order to understand how to do this.
• set_command_reg(value): set the command register
  • 0xb6: triggers a soft reset
  • 0xb0: clears all data in the FiFo
  • 0xf0: resets the acceleration data path
• set_offset_comp(on_off): enables the offset compensation for filtered and unfiltered accel data
• step_detector_enable(on_off): enables or disables the step detector feature in the sensor
• step_counter_output(): gets the number of counted steps of the step counter feature from the sensor
• step_counter_set_watermark(value): sets the watermark level for step counter interrupt in the sensor
• write_config_file(): write the binary configuration data to the sensor

The registers:

• ACCEL_CONFIG_ADDR
• POWER_CONF_ADDR
• POWER_CTRL_ADDR
• NV_CONFIG_ADDR

• ACCEL_RANGE_2G
• ACCEL_RANGE_4G
• ACCEL_RANGE_8G
• ACCEL_RANGE_16G
• ACCEL_NORMAL_AVG4
• (OUTPUT_DATA_RATE_50HZ
• OUTPUT_DATA_RATE_100HZ
• CIC_AVG_MODE
• CONTINUOUS_MODE

• SCALE_TEMP
• DEG
• FAHREN
• KELVIN

• STEP_CNTR
• STEP_ACT
• WRIST_WEAR
• SINGLE_TAP
• DOUBLE_TAP

Interrupts

• INTR1_MAP
• INTR2_MAP
• STEP_CNTR_INT
• ANY_MOT_INT
• NO_MOT_INT

• DIS_ALL_AXIS
• X_AXIS_EN
• Y_AXIS_EN
• Z_AXIS_EN
• EN_ALL_AXIS

-- Uli Raich - 2021-01-27

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