How to change I2C Address?

[cpagravel]

I notice that the configBlock gets written to the chip every time you want to take a measurement (in the function startMeasurement). The configBlock's first byte is the device address. Is there a nice way to change the device's address then?

[nseidle]

Great question. I noticed that too. I did a bit of testing and found that no, you cannot, as fair as I can tell, change the I2C address.

Also - you don't need to start the config block at 0x01 (I2C address register) every time. But we wanted to emulate the ST approach to eliminate as many unknowns as possible.

If anyone is able to figure out a way to change the I2C address, that would be great to know! I'll leave this open for now.

[cpagravel]

I tried writing to the register and then changing the offset and it didn't seem to work. Also, the documentation says that the I2C address is 0x52 (http://www.st.com/content/ccc/resource/technical/document/datasheet/group3/7d/85/c8/95/fb/3b/4e/2d/DM00452094/files/DM00452094.pdf/jcr:content/translations/en.DM00452094.pdf).

In the code it uses 0x29 which is 1 bit shift away from 0x52. I'm not sure how this is working if that's the case. I found another repo (https://github.com/pololu/vl53l1x-st-api-arduino) that uses the 0x52 address and it works well (though I haven't tested it's ability to change I2C address yet).

So why is this one using 0x29? If it's a bug, then why is it working?

[cpagravel]

Hmm... I could be misunderstanding how the I2C address is used. In the library I referenced above, the function for changing the device address shifts the input address by 2 before writing to the register.

[nseidle]

Within I2C the last bit of the first byte is the read/write bit. So the 'industry' gives addresses as 'unshifted 7-bit address'. I hate to say google it but it's fairly common at this point. Many/most datasheets for I2C devices will list the 7-bit address.

Of course the ST datasheet makes me a liar ;) But when using Arduino (and ST's example code for that matter), you would use

Wire.beginTransmission(0x29) 

Arduino docs

[cpagravel]

Ah, that's odd to incorporate the read/write bit as apart of the address. Thank you for clarifying.

[ralphhipps]

is there a way to use something similar to this to change the address on the ST sensor so you can have two or more on the same bus?

[ralphhipps]

Wire.beginTransmission(0x29) would be joining as a slave, yes?

what if the Arduino is the master and you want to have > 1 slave?

this seems to work but I lose access to the sensor afterwards, of course, as the libs all want 0x29:

Serial.println("update L1X I2C address");
distanceSensor.writeRegister(0x01, 0x28);

[nseidle]

Currently it does not look like ST has built support for changing the sensor's I2C address. Because of this, the only way to use multiple sensors is to have two buses (such as the Teensy has two Wire ports) or use a multiplexer like our Qwiic Mux Breakout.

[ralphhipps]

you may be correct, I'm having trouble with it. It seems you can write to the register to change it, sure, but it breaks communication with the sensor. I'm not a sw whiz, so I can't tell you why. A friend is using the VL53L0X and he can change the address no problem, but perhaps the VL53L1X doesn't support that. Ralph

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On Wed, Aug 29, 2018 at 6:47 AM, Nathan Seidle ***@***.***> wrote: Currently it does not look like ST has built support for changing the sensor's I2C address. Because of this, the only way to use multiple sensors is to have two buses (such as the Teensy has two Wire ports) or use a multiplexer like our Qwiic Mux Breakout <https://www.sparkfun.com/products/14685>. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#7 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ALo53GOMADbbz8ToXOufaHpJ4mCREF5Gks5uVpuLgaJpZM4T-S7z> .

[cpagravel]

Sorry, I should've commented earlier.

I followed the instructions described here: https://www.pololu.com/file/0J1239/VL53L0X-AN4846.pdf

To summarize the document:

1. Put all the Vl53L1x chips on the same I2C bus
2. Connect each reset button to a separate I/O pin
3. Change the address of the sensors one at a time

[ralphhipps]

have you tried this? I can't get it to work. how do you do this on an Arduino with the given libs? it would seem you need to have a lib from ST to make it work: 2.2 VL53L0X API management See also “VL53L0X_API_Integration Guide.pdf” on www.st.com/VL53L0X in “Design Resources” page. In vl53L0x_platform.h API file • Set VL53L0x_SINGLE_DEVICE_DRIVER macro to 0 so that API implementation will be automatically adapted to a multi-device context. • Define VL53L0xDev_t type as a structure pointer holding any data required for multidevice management. A mandatory field is an instance of VL53L0xDevData containing ST API private data. • Then – define, “N” the number of VL53L0X (Struct MyVL53L0xDev_t BoardDevs[N]) – Put all devices under reset – Enable VL53L0X one after the other and set their I2C address through VL53L0X_SetDeviceAddress (&BoardDevs[i], FinalI2cAddr) Ralph

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On Wed, Aug 29, 2018 at 8:41 AM, cpagravel ***@***.***> wrote: Sorry, I should've commented earlier. I followed the instructions described here: https://www.pololu.com/file/ 0J1239/VL53L0X-AN4846.pdf To summarize the document: 1. Put all the Vl53L1x chips on the same I2C bus 2. Connect each reset button to a separate I/O pin 3. Change the address of the sensors one at a time — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#7 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ALo53Nk5ON8FUBh82fE9M6h_D8pbspN3ks5uVrY1gaJpZM4T-S7z> .

[cpagravel]

I have tried it and it works. I used the library from Pololu though. https://www.pololu.com/product/3415/resources

It's a bit heavier, but it incorporates code written by ST.

[ralphhipps]

you tried it on the VL53L0X or the VL53L1X? Ralph

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| /\ |___/ \ [_@_] `< O O O DL Robotics! ------------------------------------------------------------------------------------ In the twenty-first century, the robot will take the place which slave labor occupied in ancient civilization. -- Nikola Tesla ------------------------------------------------------------------------------------

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On Wed, Aug 29, 2018 at 9:15 AM, cpagravel ***@***.***> wrote: I have tried it and it works. I used the library from Pololu though. https://www.pololu.com/product/3415/resources It's a bit heavier, but it incorporates code written by ST. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#7 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ALo53EcW7T4EIbYjLwe7PRkS7C5OLEbNks5uVr4ggaJpZM4T-S7z> .