Rpi4B python I2C AK8963C magnetometer sensor troubleshooting problem

Question

While attempting to read data from an ak8963c sensor board over i2c I am only getting 0s as a response except when reading the first 2 registries. I have checked my connections and tried other devices but they all work as expected. I also tried placing a magnet nearby in the hopes interference would be overpowered by said magnet.

Code:

import smbus
import time
CHL = 1
#AK8963 registers
AK8963_ADDR   = 0x0C
AK8963_ST1    = 0x02
HID      = 0x00
HX       = 0x03
HY       = 0x05
HZ       = 0x07
AK8963_ST2   = 0x09
AK8963_CNTL  = 0x0A
mag_sens = 4900.0 # magnetometer sensitivity: 4800 uT

bus = smbus.SMBus(CHL)


print('recording data')

#val = bus.read_i2c_block_data(AK8963_ADDR, HXH, 6)
val = bus.read_byte_data(AK8963_ADDR, HX)
valH = bus.read_byte_data(AK8963_ADDR, HX+1)
#mx = (val[0] << 8) | val[1]
#my = (val[2] << 8) | val[3]
#mz = (val[4] << 8) | val[5]
mx = (valH << 8) | val

val = bus.read_byte_data(AK8963_ADDR, HY)
valH = bus.read_byte_data(AK8963_ADDR, HY+1)
my = (valH << 8) | val

val = bus.read_byte_data(AK8963_ADDR, HZ)
valH = bus.read_byte_data(AK8963_ADDR, HZ+1)
mz = (valH << 8) | val

misc = bus.read_byte_data(AK8963_ADDR, 0x00)



print('{}'.format('-'*50))
#print('mag [uT]:   x = , y = , z = '.format(mx,my,mz))
print('mag [uT]:    x= % 2d, y= % 2d, z= % 2d, misc= % 2d' %(mx, my, mz, misc))
print('{}'.format('-'*50))

Answer 1

Keeper317, Since this a hardware-software interface issue, having just the code is limiting. Reading the data sheet, there are a couple of inconsistencies in your code. First, You must check for a ‘data ready’ before reading the values. This can be accomplished by polling either the data ready pin, or reading the data ready register. After reading the value, you must read the ST2 register to signal your done with the current read. Here’s a snippet from the data sheet:

6. 4.3.2. NormalReadSequence (1) Check Data Ready or not by any of the following method. - Polling DRDY bit of ST1 register - Monitor DRDY pin When Data Ready, proceed to the next step. (2) Read ST1 register (not needed when polling ST1) DRDY: Shows Data Ready or not. Not when “0”, Data Ready when “1”. DOR: Shows if any data has been skipped before the current data or not. There are no skipped data when “0”, there are skipped data when “1”. (3) Read measurement data When any of measurement data register (HXL ~ HZH) or ST2 register is read, AK8963 judges that data reading is started. When data reading is started, DRDY bit and DOR bit turnes to “0”. (4) ReadST2register(required) HOFL: Shows if magnetic sensor is overflown or not. “0” means not overflown, “1” means overflown. When ST2 register is read, AK8963 judges that data reading is finished. Stored measurement data is protected during data reading and data is not updated

Read the full data sheet here AK8963 Data Sheet