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begin() Method Corrupts Sensor ID If Not Valid about adafruit_bme280_library HOT 11 CLOSED

adafruit commented on July 4, 2024

begin() Method Corrupts Sensor ID If Not Valid

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Comments (11)

caternuson commented on July 4, 2024

When I called the begin() method using I2C and passing the correct address, it returned false and a subsequent call to the sensorID() method returned 0xFF

Hmmm. A false return from a call to begin() means something happened and you can't really expect any subsequent calls, like to sensorID(), to actually work. Basically you just have to stop and figure out what's wrong.

Looks like the example even has some commentary about this?

Adafruit_BME280_Library/examples/bme280test/bme280test.ino

Lines 47 to 53 in 616c729

    
           if (!status) { 
        
               Serial.println("Could not find a valid BME280 sensor, check wiring, address, sensor ID!"); 
        
               Serial.print("SensorID was: 0x"); Serial.println(bme.sensorID(),16); 
        
               Serial.print("        ID of 0xFF probably means a bad address, a BMP 180 or BMP 085\n"); 
        
               Serial.print("   ID of 0x56-0x58 represents a BMP 280,\n"); 
        
               Serial.print("        ID of 0x60 represents a BME 280.\n"); 
        
               Serial.print("        ID of 0x61 represents a BME 680.\n");

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gt500sc commented on July 4, 2024

Thanks for your reply, but I don't really agree with this reasoning, especially because the library is doing something I didn't tell it to do. I provided the I2C address I wanted the library to use and if it did not try the other address, the sensorID value would be intact. With the change that I suggested, the library would only try multiple I2C addresses if one wasn't explicitly passed. In either case, if there was some other kind of error, like the device was just not found, I would expect that nothing beyond begin() would work and that the sensorID() method would also return an error.

…

On 12/4/19 4:37 PM, Carter Nelson wrote: When I called the begin() method using I2C and passing the correct address, it returned false and a subsequent call to the sensorID() method returned 0xFF Hmmm. A false return from a call to |begin()| means something happened and you can't really expect any subsequent calls, like to |sensorID()|, to actually work. Basically you just have to stop and figure out what's wrong. Looks like the example even has some commentary about this? https://github.com/adafruit/Adafruit_BME280_Library/blob/616c7290e4a1bf863021506fe8367e924881cc80/examples/bme280test/bme280test.ino#L47-L53 — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#69?email_source=notifications&email_token=AGFP2HMBZP37RUMLOMSV3ADQXBEK5A5CNFSM4JR4GPD2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEF7BQSA#issuecomment-561911880>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AGFP2HIH2XN77YBTKDCX3D3QXBEK5ANCNFSM4JR4GPDQ>.

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caternuson commented on July 4, 2024

In general, it's up to you to check the return from begin(). If it's false, then your code should act accordingly, i.e. stop and not call anything else. But if you do make additional calls, you should expect unknown results. So for example, here:

When I called the begin() method using I2C and passing the correct address, it returned false and a subsequent call to the sensorID() method returned 0xFF.

You should have investigated why begin() returned false and generally ignored the return from sensorID().

Your original issue was from using this library with a different sensor. If you use it with the correct sensor, do you still have issues? If the auto-switching to alternate address does not work as expected with that arrangement, then that's something that could be investigated.

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gt500sc commented on July 4, 2024

Carter, I understand what you're saying - I agree that the initial issue was due to the wrong sensor being used, but let's take a look at another situation. Let's say I have two legit BME280 sensors, one on 0x77 and one on 0x76, and I want to use both of them concurrently. In this case, I would do something like: Adafruit_BME280 bme1; Adafruit_BME280 bme2; bool rc1 = bme1.begin(0x77); bool rc2 = bme2.begin(0x76); bme1 is found and is a valid BME280 so rc1 = true. bme2 for whatever reason fails. rc2 should be false, but the way begin() currently works, it will then try 0x77 and find the existing bme1 sensor and return true. Now my program thinks I have two good sensors, but in reality they're both pointing to the same address. If the changes I proposed were implemented, 0x77 would not be tried when 0x76 failed because I explicitly passed in the address I wanted to use. Would this situation warrant consideration? Thanks, Greg

…

On 12/5/19 8:43 AM, Carter Nelson wrote: In general, it's up to you to check the return from |begin()|. If it's |false|, then your code should act accordingly, i.e. stop and not call anything else. But if you do make additional calls, you should expect unknown results. So for example, here: When I called the begin() method using I2C and passing the correct address, it returned false and a subsequent call to the sensorID() method returned 0xFF. You should have investigated why |begin()| returned false and generally ignored the return from |sensorID()|. Your original issue was from using this library with a different sensor. If you use it with the correct sensor, do you still have issues? If the auto-switching to alternate address does not work as expected with that arrangement, then that's something that could be investigated. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#69?email_source=notifications&email_token=AGFP2HLG4NORF6AIKU6ECR3QXEVSXA5CNFSM4JR4GPD2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEGBKXRQ#issuecomment-562211782>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AGFP2HLAQ6BWB63HKOC6J33QXEVSXANCNFSM4JR4GPDQ>.

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ladyada commented on July 4, 2024

greg, with two sensors you would check both returns. we have no plans to add a check per function.
if you submit a lightweight PR we'll look at merging it!

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gt500sc commented on July 4, 2024

@ladyada my example above is checking both returns and I'm not really sure what you're saying about not adding a check per function, but I submitted a PR with my changes. My first PR so I hope I did it right. Thanks!

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caternuson commented on July 4, 2024

The two BME280 sensor case, one good + one bad, does seem more interesting. The good one will mask the bad one and the code will run, just not as expected. I could see how that would be confusing.

@ladyada Do you know the history for this "try the alternate address" logic? Why not just keep it simple and only try the address provided?

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ladyada commented on July 4, 2024

im p. sure it was a 'well meaning' PR, because folks use non-adafruit sensors and get confused when they 'dont work' - we should revert it, tho

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caternuson commented on July 4, 2024

So revert to simple? No fancy "try the alternate address" logic?

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ladyada commented on July 4, 2024

yeah!

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caternuson commented on July 4, 2024

@gt500sc Do you want to try changing your PR to make that happen? This is essentially much simpler. There's no logic needed at all. Just try to init with the supplied address and return status. If no address is specified, just use a default (that would be handled via the overloaded c-tors).

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begin() Method Corrupts Sensor ID If Not Valid about adafruit_bme280_library HOT 11 CLOSED

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	if (!status) {
	Serial.println("Could not find a valid BME280 sensor, check wiring, address, sensor ID!");
	Serial.print("SensorID was: 0x"); Serial.println(bme.sensorID(),16);
	Serial.print(" ID of 0xFF probably means a bad address, a BMP 180 or BMP 085\n");
	Serial.print(" ID of 0x56-0x58 represents a BMP 280,\n");
	Serial.print(" ID of 0x60 represents a BME 280.\n");
	Serial.print(" ID of 0x61 represents a BME 680.\n");