i2c device not visible

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zmemw16
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i2c device not visible

Post by zmemw16 » Sat Feb 10, 2018 10:32 pm

i've a few i2c 0.96" displays, pins in sequence vcc, gnd, sda, scl, so thought i'd test them.
i also have some sip resistor packs, 4 off 4k7 with pin 1 as the common, so it adds pullups on scl & sda :)
vcc is taken from the lolin v3 esp8266 board vin pin, hence in general not libs & h/ware :)
i know vin does supply enough for the 1.3" 4pin spi oleds i'd tested earlier

so for the breadboard, i put the sip pin 1 to vcc, i2c scanner zilch
4k7 across vcc to gnd shouldn't be a problem, right ?

remove sip and up she popped at 0x3c

any thoughts or is it just strange

stephen
Last edited by zmemw16 on Sun Feb 11, 2018 12:57 am, edited 1 time in total.

stevestrong
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Re: i2c device not visible

Post by stevestrong » Sat Feb 10, 2018 10:39 pm

Which core?
I think we had some issues with an application using two I2C devices connected to the same I2C port, but cannot remember what exactly it was.

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RogerClark
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Re: i2c device not visible

Post by RogerClark » Sat Feb 10, 2018 10:46 pm

There have been some reports not being able to operate different I2C device libraries on the same bus.

I don't think anyone has determined if these is a problem with specific libraries or whether all libraries are effected (due to problems with the Hardware I2C library)

You could try using the version prior to the change to use Hardware I2C

https://github.com/rogerclarkmelbourne/ ... 901e522dac

zmemw16
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Re: i2c device not visible

Post by zmemw16 » Sun Feb 11, 2018 12:55 am

when i test displays it's one at a time, even on spi, but particularly so on i2c :)

core it's the esp8266 official one - i did say

the point i was getting at was that it worked when i removed the sip resistor pack, at least as far as the 'official' i2c scanner was concerned.
not seen any snowflakes as yet :D

srp

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RogerClark
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Re: i2c device not visible

Post by RogerClark » Sun Feb 11, 2018 3:02 am

Its possible that you'll need to comment out the include for the other I2C lib, as its constructor may interfere with the operation

zmemw16
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Re: i2c device not visible

Post by zmemw16 » Sun Feb 11, 2018 4:03 am

@Roger
what other i2c lib ? there ain't one !
the example code i ctl-c'd it and ctl-v'd in from a esp8266 example on the www, only has Wire.h in it - this is the esp8266 core so it's doubtful if they're also done the renaming of (Wire to HardWire ?) ?

with 4k7 sip in circuit, i2c scanner 120 odd error messages saying nothing found; remove sip and a single line indicates a device @ 0x3c is seen.
i'm just puzzled as to why / how ?

stephen

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RogerClark
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Re: i2c device not visible

Post by RogerClark » Sun Feb 11, 2018 5:06 am

@zmemw16

Some people have reported issues with multiple different types of I2C devices on the same bus.

Our guess was that there is possibly a problem with the Hardware I2C doing something there its not possible 2 or libs all using HardWire

However no one has really confirmed whether there is definitely an issue

zmemw16
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Re: i2c device not visible

Post by zmemw16 » Sun Feb 11, 2018 3:12 pm

stephen wrote
i've a few i2c 0.96" displays, pins in sequence vcc, gnd, sda, scl,
all of the same type. and observing the missing resistors makes them i2c at 0x3c

when nothing i2c is working, my response is to scan for i2c devices indirectly testing them one at a time.
i've nver had 2 of these on the same bus or even on multiple interfaces, first option needs the soldering iron, second one just never.
so esp8266 core, wire.begin(D2, D4), 4k7 4 resistors in 5 pin sip and one display is the hardware.
the sip has pin 1 aligned with vcc of display
there is then via the sip internals, a 4k7 resistor from each of gnd, sda & scl pins to vcc(vin on lolin v3)

no device is seen
remove sip, it's seen at 0x3c

4k7 across 5v is 1mA, off to find multimeter, said sips came from CPC, will report back :?

stephen

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Re: i2c device not visible

Post by stevestrong » Sun Feb 11, 2018 6:04 pm

zmemw16 wrote:
Sun Feb 11, 2018 3:12 pm
esp8266 core
What is the link to any of the STM32 cores?

zmemw16
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Re: i2c device not visible

Post by zmemw16 » Sun Feb 11, 2018 7:16 pm

ok, it should have gone in off topic, i'd thought not into libs & hardware, hence general :-)

it was just a bit quirky and puzzled me.
actually that's probably a reasonable description of me as well. puzzled is pretty much the norm !

stephen

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