Sebastián: Is your Arduino 3.3V or 5.0 V I/O?
What clock speed are you running the I2C bus in the Beaglebone? With the time distortion in the level translator, I would not go above 100 kHz until proven good at higher speeds. I note that your schematic shows VDDP connected to 5V. This should be connected to the same reference Voltage as the I2C bus is using, which is 3.3V in the case of the Beaglebone. I have not digested the ADM3260 data sheet sufficiently to understand if it is OK to run both buses at 3.3V, and the power supply input at 5V. Is this what you are actually doing when on the Beaglebone? --- Graham == On Fri, Jun 16, 2017 at 12:34 PM, Sebastián Sáez <otra...@gmail.com> wrote: > This are the value in hexadecimal of the 25 registers in the sensor, check > with datasheet and it's ok > > 1,4,1,65,0,1,0,1,0,0,0,0,0,0,0,0,9,C4,0,0,9,C4,0,0,16 > > > I used arduino to read this, I discovered that what I read with python is > garbage > > On Friday, June 16, 2017 at 12:43:14 PM UTC-4, Sebastián Sáez wrote: >> >> Hi Graham, thanks >> >> here more info >> >> HW: Beaglebone seeedstudio green wireless >>> OS: Debian GNU/Linux 8.8 (jessie) >>> Kernel: Linux beaglebone 4.4.30-ti-r64 >>> Python: Python 2.7.9 >> >> >> I made a custom cape, the sensor it's power with 3.3v and conected to >> I2C_2 through an isolator >> >> SDA -> P9.20 >> SCL -> P9.19 >> >> >> <https://lh3.googleusercontent.com/-LQRB-CkLTZo/WUQGKC1Q1bI/AAAAAAAADKA/bTmen-ZCt0gd_AsHUnmU78UUmiNiZ3-9wCLcBGAs/s1600/Untitled.png> >> >> The HW it's OK, I check with an arduino and example code and I can write >> registers with my python script on the beaglebone. >> >> The ph sensor is in 0x65 address and other Atlas sensor in 0x64 >> >> debian@beaglebone:~$ i2cdetect -y -r 2 >> 0 1 2 3 4 5 6 7 8 9 a b c d e f >> 00: -- -- -- -- -- -- -- -- -- -- -- -- -- >> 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- >> 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- >> 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- >> 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- >> 50: -- -- -- -- UU UU UU UU -- -- -- -- -- -- -- -- >> 60: -- -- -- -- 64 65 -- -- -- -- -- -- -- -- -- -- >> 70: -- -- -- -- -- -- -- -- >> >> Now I can write register with this script (can on/off onboard LED) but >> when I try to read all 25 register I get this >> >> >>> 1, 1, 0, 0, 0, 0, 0, 0, 9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 >> >> >> The first 2 bytes are the ID and FW, but I expect the rest to have values >> such as the pH (registers 0x16, 0x17, 0x18, 0x19) but I am getting only 0 >> (garbage) >> >> Python script >> import smbus >> import time >> >> class i2c_device: >> def __init__(self, addr, port): >> self.addr = addr >> self.bus = smbus.SMBus(port) >> >> def write(self, byte): >> self.bus.write_byte(self.addr, byte) >> >> def write_i2c_block_data(self, byte, array): >> self.bus.write_i2c_block_data(self.addr, byte, array) >> >> def read(self): >> return self.bus.read_byte(self.addr) >> >> def read_nbytes_data(self, data, n): # For sequential reads > 1 byte >> return self.bus.read_i2c_block_data(self.addr, data, n) >> >> ph = i2c_device(0x65, 2) >> ph.write(0x00) >> i=0 >> while (i <= 25): >> print(ph.read()) >> time.sleep(0.5) >> i+=1 >> >> >> >> >> On Thursday, June 15, 2017 at 10:38:28 PM UTC-4, Graham wrote: >>> >>> OK. >>> Let's start with some background information. >>> What model of Beaglebone? >>> What version of OS, kernel? >>> Which version of Python? >>> How is the pH sensor hooked to the Beaglebone? >>> What Voltage are you using to power the pH sensor? >>> >>> Now some basics to see if the I2C bus is running >>> >>> sudo apt-get install i2c-tools >>> >>> now run >>> i2cdetect -y -r 1 >>> what do you get? >>> >>> now run >>> i2cdetect -y -r 2 >>> what do you get? >>> >>> When you say that you get "garbage" what do you mean? >>> What do you actually get? errors? tracebacks? obviously wrong data, but >>> no reported errors? >>> >>> --- Graham >>> >>> == >>> >>> On Thursday, June 15, 2017 at 5:38:58 PM UTC-5, Sebastián Sáez wrote: >>>> >>>> >>>> Hi, >>>> >>>> I'm writing a python script to communicate via i2c with the ph oem >>>> sensor from Atlas Scientific. >>>> >>>> https://www.atlas-scientific.com/product_pages/oem/oem_ph.html >>>> https://www.atlas-scientific.com/_files/_datasheets/_oem/pH_ >>>> oem_datasheet.pdf >>>> >>>> I already tried with the i2c module of mraa and smbus without luck. >>>> Now I am trying to translate this arduino example from Atlas to python >>>> but I read garbage >>>> >>>> >>>> Any suggestions?, attached the full example arduino code >>>> >>>> >>>> *Atlas arduino code* >>>> byte i2c_device_address=0x65; >>>> byte starting_register=0x00 >>>> byte device_type; >>>> byte version_number; >>>> Wire.beginTransmission(i2c_device_address); >>>> Wire.write(staring_register); >>>> Wire.endTransmission(); >>>> Wire.requestFrom(i2c_device_address,(byte)2); >>>> device_type = Wire.read(); >>>> version_number = Wire.read(); >>>> Wire.endTransmission(); >>>> >>>> >>>> *My python script* >>>> import smbus >>>> >>>> # General i2c device class so that other devices can be added easily >>>> class i2c_device: >>>> def __init__(self, addr, port): >>>> self.addr = addr >>>> self.bus = smbus.SMBus(port) >>>> >>>> def write(self, byte): >>>> self.bus.write_byte(self.addr, byte) >>>> >>>> def read(self): >>>> return self.bus.read_byte(self.addr) >>>> >>>> def read_nbytes_data(self, data, n): # For sequential reads > 1 byte >>>> return self.bus.read_i2c_block_data(self.addr, data, n) >>>> >>>> ph = i2c_device(0x65, 2) >>>> ph.write(0x00) >>>> device_type = ph.read() >>>> version_number = ph.read() >>>> print(device_type) >>>> print(version_number) >>>> >>>> >>>> -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to a topic in the > Google Groups "BeagleBoard" group. > To unsubscribe from this topic, visit https://groups.google.com/d/ > topic/beagleboard/Lyxv7E3yIvs/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > beagleboard+unsubscr...@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/ > msgid/beagleboard/589b19eb-9c6a-4ed9-aca3-3f3f1241ed4b%40googlegroups.com > <https://groups.google.com/d/msgid/beagleboard/589b19eb-9c6a-4ed9-aca3-3f3f1241ed4b%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > For more options, visit https://groups.google.com/d/optout. > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. 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