SPI - Pyboard and ADXL345

[TradUncle]

Hi,

I have been banging my head against the wall trying to get this code to work. I have adapted old code that had several errors, and have had no luck getting accel data off the ADXL345.

The only thing I've managed is reading the register for the device ID, which is correct and reads 0xe5. After reading, the next thing that happens is I write to all the ADXL registers to setup the device.

However, after this happens, reading any other register over SPI just returns the same 0xe5 repeatedly. The image below shows an attempt at reading the POWER_CTRL register and DATA registers, which all return 0xe5.

REPL output

The sensor works with I2C, I don't have access to an oscilloscope, and the pin connections are correct and using SPI(1). In-case I've missed something obvious, I've attached an image of the current attachment.

There is something simple I'm missing, but I need another pair of eyes to tell me where I've gone wrong because I can't figure it out. Any help would be appreciated.

ADXL Datasheet

https://www.analog.com/media/en/technical-documentation/data-sheets/ADXL345.pdf

Wiring Setup

main.py

import pyb
from adxl345 import AD345
from machine import SPI

# Red LED indicator that code ran. If not on, board had an error.
error_led = pyb.LED(1)
error_led.on()

# code modified from https://github.com/AbhinayBandaru/ADXL345-with-Pyboard

spi_on = pyb.LED(2) # led for when SPI is communicating

switch = pyb.Switch()

adxl = AD345()

print("SENSOR ID: %s" % (hex(adxl.read_id())))

while True:

    pyb.wfi() # wait for interrupt e.g. the switch being pressed

    if switch():
        pyb.delay(200)
        spi_on.on()
        while not switch():
            t = pyb.millis()
            x, y, z = adxl.xyz()

            print('time:', t)
            print('X Axis :',x)
            print('Y Axis :', y)
            print('Z Axis :', z)

        spi_on.off()
        pyb.delay(200)

adxl345.py

from machine import SPI
import pyb
from pyb import Pin
from micropython import const

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)
# Configuration for 100Hz sampling rate, +-2g range
ADXL345_POWER_CTL_CONF = const(0x08)
ADXL345_POWER_CTL_INIT = const(0x00)
ADXL345_BW_RATE_CONF = const(0b1111)
ADXL345_DATA_FORMAT_CONF = const(0x10)
ADXL345_ENABLE_MSRM_CONF = const(0x08)


class AD345:
    def __init__(self):
        self.spi = SPI(1, baudrate=2000000, polarity=1, phase=1, bits=8)
        self.spi.init(baudrate=2000000, polarity=1, phase=1, bits=8)
        pyb.delay(200)
        self.cs_pin = Pin('X5', Pin.OUT_PP, Pin.PULL_NONE)
        self.cs_pin.high()
        pyb.delay(200)

        self.devid = self.read_id()

        # ADXL setup code
        if self.devid == ADXL345_DEVID_VAL:
            # self.write_bytes(ADXL345_POWER_CTL_ADDR, bytearray([ADXL345_POWER_CTL_INIT]))
            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

            print("Power Ctrl Contents Read: %s" % (hex((self.read_bytes(ADXL345_POWER_CTL_ADDR, 1)[0]))))
        else:
            raise Exception('ADXL345 accelerometer not present')

    def convert_raw_to_g(self, x):
        if x & 0x80:
            return x * self.sensitivity / 1000

    def read_bytes(self, addr, nbytes):
        if nbytes > 1:
            addr |= READWRITE_CMD | MULTIPLEBYTE_CMD
        else:
            addr |= READWRITE_CMD
        self.cs_pin.low()

        # self.spi.write(bytearray(addr))
        buf = self.spi.read(nbytes,addr)

        self.cs_pin.high()
        return buf

    def write_bytes(self, addr, buf):
        if len(buf) > 1:
            addr |= MULTIPLEBYTE_CMD
        self.cs_pin.low()

        self.spi.write(bytearray(addr))
        for b in buf:
            self.spi.write(bytearray(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())