I2C sensor with WiPy2

SesamProductions

(sysname='WiPy', nodename='WiPy', release='1.7.2.b1', version='v1.8.6-650-g9bacbbd4 on 2017-06-09', machine='WiPy with ESP32')

livius

@SesamProductions
try upgrade to recent firmware because now i2c is hardware implementation not software as was previously
https://forum.pycom.io/topic/1423/new-firmware-release-1-7-5-b2

SesamProductions

@livius Thanks for the tip, I had not noticed that there were new firmwares out. Unfortunately it didn't help.
Do I have to make any changes to my code with this?

I have now tried this with two different WIPy2 borads with the most recent firmware. I have also tried with two different identical sensor boards, as well as three other i2c-devices, none gives any sensible output to the WiPy, but all work well with Arduinos.

I did notice one thing that could possibly be relevant, although I have no idea how.
This is a readout made just after reboot:

>>> os.uname()
(sysname='WiPy', nodename='WiPy', release='1.7.6.b1', version='v1.8.6-703-g5e80328a on 2017-07-05', machine='WiPy with ESP32')
>>> from machine import I2C
>>> i = I2C(0, I2C.MASTER)
>>> i.scan()
[41, 57, 87, 104]
>>> i.readfrom_mem(0x29, 0, 1)
b'\xb4'
>>> i.readfrom_mem(0x29, 0, 1)
b'\x01'
>>> i.readfrom_mem(0x29, 0, 1)
b'\x03'
>>> i.readfrom_mem(0x29, 0, 1)
b'\x01'
>>> i.readfrom_mem(0x29, 0, 1)
b'\x02'
>>> i.readfrom_mem(0x29, 0, 1)
b'r'
>>> i.readfrom_mem(0x29, 0, 1)
b'C'
>>> i.readfrom_mem(0x29, 0, 1)
b'\xe9'
>>> i.readfrom_mem(0x29, 0, 1)
b'\xa0'

The first response, b'\xb4', is the correct one, but should not change. The commands are sent about one second apart.
The interesting thing is that the response sequence is always identical, with both sensors and both boards, it's always:
b'\xb4'
b'\x01'
b'\x03'
b'\x01'
and so on.

I have absolutely no idea what's wrong or what to try next and will appreciate any help!

robert-hh

@SesamProductions So it looks as if instead just the first byte all registers of the first group are transferred. I wonder why you use i2c.readfrom_mem(), since this is not a memory device. I would expect that you first have to send the register address with i2c.writeto() and then read back the intended number of bytes with i2c.readfrom().

SesamProductions

@robert-hh Thanks for that insight, that turned out to be exactly what's happening! And after doing a closer inspection in the datasheet I found this sentence:
"After the first data byte has been transferred, the index is automatically incremented by 1."
Now on to learning how to use that feature.

Regarding i2c.readfrom_mem()
I might have missunderstood how it works, but how can I read a specific device register without it?
The machine-module documentation says in connection to readfrom_mem:
"Some I2C devices act as a memory device (or set of registers)", and I interpreted that to mean that it's the function to use when targeting a specific register.
Is that instead referring to devices with some other register functionality?

I just now tried doing i2c.writeto(0x29, 0), which returned 1, and then i2c.readfrom(0x29, 1), but it didn't return any useful values, mostly zeroes but sometimes other values. If I understood your suggestion correct that should have given me the 'b4' I want.

livius

@SesamProductions
If you look at C library
you must do much more work to work with this sensor
https://github.com/pololu/vl6180x-arduino/blob/master/VL6180X.cpp

Eric24

@SesamProductions said in I2C sensor with WiPy2:

VL6180x

Yes, this is a fairly complex device that requires a lot of initialization (although I would think reading back the model ID could be done without init, but who knows). We used this driver: https://github.com/luciengaitskell/python-adafruit-vl6180x/blob/master/i2c/vl6180x.py

We've since moved on from using this sensor (it's a very interesting device, but it did not work well in our particular application), but I had no problem communicating with it. In fact, the only problems I've ever had with I2C on any pycom device was with the lack of clock stretching support on the software-based I2C (and now that hardware-based I2C is supported, that's no longer a problem).

robert-hh

@SesamProductions From the spec, I assume that the sequence should be:

i2c.writeto(0x29, b'\x00\x00')
i2c.readfrom(0x29, 1)

The address for a read is a two byte value.

iotmaker

I have it working like this

VL53L0X_REG_IDENTIFICATION_MODEL_ID=0xc0
VL53L0X_REG_IDENTIFICATION_REVISION_ID=0xc2
VL53L0X_REG_PRE_RANGE_CONFIG_VCSEL_PERIOD=  0x50
VL53L0X_REG_FINAL_RANGE_CONFIG_VCSEL_PERIOD=0x70
VL53L0X_REG_SYSRANGE_START=0x00
VL53L0X_REG_RESULT_INTERRUPT_STATUS=0x13
VL53L0X_REG_RESULT_RANGE_STATUS=0x14
sensor= 0x29#I2C Address


print("Revision ID ")
print(i2c.readfrom_mem(sensor,VL53L0X_REG_IDENTIFICATION_REVISION_ID,1))
print("")
print("Device ID ")
print(i2c.readfrom_mem(sensor,VL53L0X_REG_IDENTIFICATION_MODEL_ID,1))
print("")
print("Pre Range config Period")
print(i2c.readfrom_mem(sensor,VL53L0X_REG_PRE_RANGE_CONFIG_VCSEL_PERIOD,1))
print("")
print("Final  Period")
print(i2c.readfrom_mem(sensor,VL53L0X_REG_FINAL_RANGE_CONFIG_VCSEL_PERIOD,1))

#To read first check the status
val=i2c.readfrom_mem(sensor,VL53L0X_REG_RESULT_RANGE_STATUS,1)

#if val is equal to 64 then it read the distance 

#read the value
 datasensor=i2c.readfrom_mem(sensor,0x14,12)#Read sensor data
    distance=datasensor[10]*256+datasensor[11]#combine integers

I have it working on the VL53L0X hope it helps

SesamProductions

Thanks for the suggestions!

@robert-hh
YES! That is working! Thank you! I can now read data from registers in a controller way.
Unfortunately I'm now very confused about this. If the writeto function is used to tell the device what register I want to read, how do I write things to the registers? For instance to tell the device I want it to start measuring range.

@iotmaker
To me it looks like you're doing the exakt same thing I'm doing, and according to the short datasheet I found for your sensor, it should work similar to mine.
So why yours is working and mine is not is definitely beyond me.

@Eric24
When I've tried the sensor on the Arduino I've used the Adafruit library your linked code seem to be a python port of. I had myself not found that python version, so what I've done is my own python port of the Adafruit Arduino library. The problem is that in order to deal with all the complexities of the sensor and initialize it, I need to be able to read and write to registers, which is the part that isn't working.
The python-version you're linking to is using a module called smbus to deal with everything I'm having problems with. Where do I get that from? I didn't find any links for that on the github page, and import smbus is not working on my WiPy. Where you using it on a WiPy, or some other Pycom device?
I had not heard about smbus before and a quick google for it seem to indicate it's a different, but fairly similar, protocol than i2c. Was there a reason for using smbus instead of the builtin i2c?

robert-hh

@SesamProductions For writing to a register, just append the data for the register to the address in a single write.
About @iotmaker's comment. The VL53L0X device he uses requires just an 1 byte address just like the memory devices.

Eric24

@SesamProductions I'm afraid I don't have any more information on that library. But smbus is just the I2C library for whatever hardware platform it was written for. You should be able to substitute pycom's I2C functions readfrom_mem and writeto_mem for b.read_byte_data and b.write_byte_data, respectively. But note, I've never actually tried to access 16-bit addresses using pycom's I2C functions. If they don't work, please do submit a bug report, and in that case, you should be able to accomplish the same thing using the writeto and readfrom method that @robert-hh suggested earlier.

SesamProductions

Great! Now I'm starting to understand this a bit!
I can read and write stuff using @robert-hh's suggestions, and the sensor seem to output correct data. Now I just have to modify my library with new read/write methods.

Thanks a lot for the help!

chumelnicu

@iotmaker Hello , can u tell me please what is maximum distance range?

chumelnicu

@iotmaker Hi , did u read distance using vl53l0x with this code? Wrking and long distance too? i mean 200cm?
Thx!

ledbelly2142

@chumelnicu
It's in the specification of the sensor, see HERE that the VL6180X can measure up to 20 cm.

The VL53L0X will measure up to 2 Meters (6.6Ft) away. You can see it on a breakout board HERE

chumelnicu

@ledbelly2142 I know the diference between VL6180X and VL53L0X ! The question has target other response and was for @iotmaker

I did asked him if he managed to read the VL53L0X in long range mode (that mean 200cm)

chumelnicu

@sesamproductions Did u manage to read VL53LX0 in long distance mode?

Thx!

JasonTimmins

@iotmaker Thanks for your code for the VL53L0X distance sensor. I've got the same configuration here and, although I can read the various registers you mention (Revision ID, Device ID, etc), I can't actually get a distance from the thing. VL53L0X_REG_RESULT_RANGE_STATUS is zero all the time and your 'distance' code gives zero too.

This looks like a fairly complex device, am I missing some kind of initialisation procedure?

Cheers
Jason.

iotmaker

@JasonTimmins

This is my full code

just clean it up hehe

from machine import UART
from time import sleep_ms
from network import Sigfox
from machine import I2C
import socket
import pycom
import re
import binascii
import ubinascii
from machine import Pin
import ustruct
import time

VL53L0X_REG_IDENTIFICATION_MODEL_ID=0xc0
VL53L0X_REG_IDENTIFICATION_REVISION_ID=0xc2
VL53L0X_REG_PRE_RANGE_CONFIG_VCSEL_PERIOD=  0x50
VL53L0X_REG_FINAL_RANGE_CONFIG_VCSEL_PERIOD=0x70
VL53L0X_REG_SYSRANGE_START=0x00
VL53L0X_REG_RESULT_INTERRUPT_STATUS=0x13
VL53L0X_REG_RESULT_RANGE_STATUS=0x14
sensor= 0x29#I2C Address


### Sigfox Stuff
sigfox = Sigfox(mode=Sigfox.SIGFOX, rcz=Sigfox.RCZ2)

# create a Sigfox socket
s = socket.socket(socket.AF_SIGFOX, socket.SOCK_RAW)

# print Sigfox Device ID
print("Sigfox ID")
print(binascii.hexlify(sigfox.id()))

# print Sigfox PAC number
print("Sigfox PAC")
print(binascii.hexlify(sigfox.pac()))

# make the socket blocking
s.setblocking(True)

# configure it as uplink only
s.setsockopt(socket.SOL_SIGFOX, socket.SO_RX, False)

#Sigfox Stuff
pycom.heartbeat(False)
##RGB Colors
red=0xff0000
yellow=0xffff00
green=0x00ff00
blue=0x0000ff
cyan=0x00feff
purple=0xc442a1
orange=0xff8b55
dark=0x000000




def ledtoggle(color):
    pycom.rgbled(color)
    sleep_ms(50)
    pycom.rgbled(dark)
    sleep_ms(50)

def i2c_w(reg,val):
    i2c.writeto_mem(sensor,reg,bytes([val]))##Put device on standby mode
    sleep_ms(1)





## address 0x1D
i2c = I2C(0)                         # create on bus 0
i2c = I2C(0, I2C.MASTER)             # create and init as a master
i2c.init(I2C.MASTER, baudrate=400000) # init as a master
sleep_ms(30)

print("I2C Scan for devices")
print(i2c.scan())
print("Revision ID ")
print(i2c.readfrom_mem(sensor,VL53L0X_REG_IDENTIFICATION_REVISION_ID,1))
print("")
print("Device ID ")
print(i2c.readfrom_mem(sensor,VL53L0X_REG_IDENTIFICATION_MODEL_ID,1))
print("")
print("Pre Range config Period")
print(i2c.readfrom_mem(sensor,VL53L0X_REG_PRE_RANGE_CONFIG_VCSEL_PERIOD,1))
print("")
print("Final  Period")
print(i2c.readfrom_mem(sensor,VL53L0X_REG_FINAL_RANGE_CONFIG_VCSEL_PERIOD,1))
sleep_ms(30)
print("")


cnt=0
val=0
a=0
while True:

    #print("Start Measuerment")
    i2c_w(VL53L0X_REG_SYSRANGE_START, 0x02)

    while (cnt < 100):
            #1 second waiting time max

        val=i2c.readfrom_mem(sensor,VL53L0X_REG_RESULT_RANGE_STATUS,1)



        if val==64:
            cnt=200
        cnt=cnt+1

    sleep_ms(30)

    datasensor=i2c.readfrom_mem(sensor,0x14,12)#Read sensor data
    distance=datasensor[10]*256+datasensor[11]#combine integers
    #print("distance")
    print(distance)
    if 100<=distance<=200:
            print('Sending Sigfox')
            s.send(bytes([datasensor[10], datasensor[11], 255, 255, 255, 255, 255, 255, 255, 255, 255, 255]))
            ledtoggle(blue)
            ledtoggle(blue)
            ledtoggle(blue)
            ledtoggle(blue)
            print("By law it will sleep 20 seconds")
            time.sleep(20)
    ledtoggle(green)
    # for x in range(0,12):
    #     print(datasensor[x])
    #
    # print(datasensor)

    # print(datasensor[10])
    # print(datasensor[11])
    # print("")
    sleep_ms(1000)```

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