ADXL345 with Pyboard

[Jim.S]

You are thinking too complicated at the moment. You need to break the problem down into simple parts
1. understand how to edit boot.py so that it does not mount the /flash or /sd card on the host PC (i.e uncomment the line pyb.usb_mode('CDC+HID')). If you don’t do this you will have problems logging data to a text file
2. Learn how to use the rshell.py program. Rshell is your friend. It will let you transfer your files to and from the host PC to your pyboard when the flash drive and sd card are not mounted as storage devices.
3. Write a very simple program that just writes numbers to a text file. This will teach you about the python string formatting, stuff like print('{},{},{}'.format(1,2,3)).
4. Write a simple program that creates a ADXL345Accel object using the library/driver you have posted earlier in this thread. This program should just
a) create an ADXL345Accel object
b) get the three acceleration values
c) print them to the screen (see 3 above) and exit

5. Modify the program so that it runs continuously, gets three acceleration values once a second and prints them to the screen. This will teach you how to control the speed of the program loop
6. Now put it all together. Modify the program so that it writes the values to a file but only once a second!
7. Gradually increase the speed of the program so it writes faster and faster. This will reveal all sorts of issues with your program and teach you loads.

This is exactly what I have done over the last few weeks........

[Turbinenreiter]

There is a datalogger in the examples folder of the micropython repo.

[dhylands]

Open a file and write the data (it's the same in micropython as regular python).

[markph]

[quote="Turbinenreiter"]There is a datalogger in the examples folder of the micropython repo.[/quote]

Also here: http://wiki.micropython.org/SDdatalogger

[aleskeyfedorovich]

Code: Select all

from pyb import Pin
from pyb import SPI

READWRITE_CMD = const(0x80)
MULTIPLEBYTE_CMD = const(0x40)
DEVID_ADDR = const(0x00)
DATAX1_ADDR = const(0x33)
DATAY1_ADDR = const(0x35)
DATAZ1_ADDR = const(0x37)

ADXL345_DEVID_VAL = const(0xE5)
ADXL345_POWER_CTL_ADDR = const(0x2D)
ADXL345_BW_RATE_ADDR = const(0x2C)
ADXL345_DATA_FORMAT_ADDR = const(0x31)
ADXL345_ENABLE_MSRM_ADDR = const(0x2D)

ADXL345_POWER_CTL_CONF = const(0x00)
ADXL345_BW_RATE_CONF = const(0x0F)
ADXL345_DATA_FORMAT_CONF = const(0x10)
ADXL345_ENABLE_MSRM_CONF = const(0x08)

class ADXL345Accel:
        def _init_(self):
                self.cs_pin = Pin('X5', Pin.OUT_PP, Pin.PULL_NONE)
                self.cs_pin.high()
                self.spi = SPI(1, SPI.MASTER, baudrate=2000000, polarity=0, phase=1, bits=8)
                
                self.devid = self.read_id()
                if self.devid == ADXL345_DEVID_VAL:
                      self.write_bytes(ADXL345_POWER_CTL_ADDR, bytearray([ADXL345_POWER_CTL_CONF]))
                      self.write_bytes(ADXL345_BW_RATE_ADDR, bytearray([ADXL345_BW_RATE_CONF]))
                      self.write_bytes(ADXL345_DATA_FORMAT_ADDR, bytearray([ADXL345_DATA_FORMAT_CONF]))
                      self.write_bytes(ADXL345_ENABLE_MSRM_ADDR, bytearray([ADXL345_ENABLE_MSRM_CONF]))
                      self.sensitivity = 32
                else:
                      raise Exception('ADXL345 accelerometer not present')
     def convert_raw_to_g(self, x):
             if x & 0x80:
                   x = x - 256
             return x * self.sensitivity / 1000
  def read_bytes(self, addr, nbytes):
          if len(buf) > 1:
         addr |= MULTIPLEBYTE_CMD
    self.cs_pin.low()
    self.spi.send(addr)
    for b in buff:
     self.spi.send(b) 
                 self.cs_pin.high()
        def read_id(self):
                return self.read_bytes(DEVID_ADDR, 1)[0]
        def x(self):
                return self.convert_raw_to_g(self.read_bytes(DATAX1_ADDR, 1)[0])
        def y(self):                                                                                                                                
                return self.convert_raw_to_g(self.read_bytes(DATAY1_ADDR, 1)[0])
        def z(self):
                return self.convert_raw_to_g(self.read_bytes(DATAZ1_ADDR, 1)[0])
        def xyz(self):
                return (self.x(), self.y(), self.z())

This code misses the write_bytes method, could you please provide the complete working library, please?