techpaul
Posts: 1512
Joined: Sat Jul 14, 2012 6:40 pm
Location: Reading, UK
Contact: Website

Re: I2C device responding on all addresses

Sun Dec 30, 2012 11:20 am

vortexau wrote:
techpaul wrote:What I2C clock speed do you use for the displays on Beagleboard and Arduino?

If 100kHz or lower, then would suggest display cannot work at 400kHz of Pi.
If 400kHz we need to find another solution possibly I2C repeater.
BeagleBone uses 100khz, as does Arduino. RasPi of course uses 100khz, too.
Where abouts are you as someone may be close by with a scope to measure what is happening and possibly have another Pi that can be used
Just another techie on the net - For GPIO boards see http:///www.facebook.com/pcservicesreading
or http://www.pcserviceselectronics.co.uk/pi/

vortexau
Posts: 28
Joined: Fri Dec 28, 2012 6:11 am

Re: I2C device responding on all addresses

Sun Dec 30, 2012 11:26 am

techpaul wrote:One other thought has the OP tried a second Pi?
Yep, 256mb RasPi and a new 512mb (which was the first board I tried). Same result.

vortexau
Posts: 28
Joined: Fri Dec 28, 2012 6:11 am

Re: I2C device responding on all addresses

Sun Dec 30, 2012 11:27 am

techpaul wrote:
vortexau wrote:
techpaul wrote:What I2C clock speed do you use for the displays on Beagleboard and Arduino?

If 100kHz or lower, then would suggest display cannot work at 400kHz of Pi.
If 400kHz we need to find another solution possibly I2C repeater.
BeagleBone uses 100khz, as does Arduino. RasPi of course uses 100khz, too.
Where abouts are you as someone may be close by with a scope to measure what is happening and possibly have another Pi that can be used
Adelaide, Australia. We have a Hackerspace here, I've considered asking if anyone there can help - but it can be tough with a young family.

techpaul
Posts: 1512
Joined: Sat Jul 14, 2012 6:40 pm
Location: Reading, UK
Contact: Website

Re: I2C device responding on all addresses

Sun Dec 30, 2012 11:30 am

vortexau wrote:
techpaul wrote:Where abouts are you as someone may be close by with a scope to measure what is happening and possibly have another Pi that can be used
Adelaide, Australia. We have a Hackerspace here, I've considered asking if anyone there can help - but it can be tough with a young family.
If someone in Adelaide area with a digital scope can help this poster, it would be appreciated. It would greatly help if they have a scope that can capture a trace so that can be sent to the designer to show what is happening on I2C at power up and during i2cdetect.
Just another techie on the net - For GPIO boards see http:///www.facebook.com/pcservicesreading
or http://www.pcserviceselectronics.co.uk/pi/

bitmaster
Posts: 1
Joined: Sun Jan 11, 2015 11:10 pm

Re: I2C device responding on all addresses

Sun Jan 11, 2015 11:39 pm

2 1/2 years later.
I have a Akafugu I2C lcd board. Same problem.

I used a Adafruit level convertor between the Rasp b+ and the Akafugu board.
No additional pullups are needed and the I2C speed is 100k.
With my scope connected I saw some strange behavior when using the command gpio i2cdetect.
During the scan process the rasp b+ sets the r/w bit high at some addresses. This was the case for my default Akafugu board address 50(dec).
And when the r/w bit is high, the Akafugu board pulls the SDA line to 0V and never releases the line.
So all the other checks with i2cdetect will result in that all addresses have a i2c device connected. This is not the real situation.
I solved this problem by reprogramming the Akafugu board with address 45(dec). When using i2cdetect on the rasp b+ it sends the r/w bit low for this address. The Akafugu board responds with an Ack. Problem solved!
Question is still: why this strange behaviour? i2cdetect responds for some addresses with the r/w bit low and other addresses high?

okaysh
Posts: 1
Joined: Mon Jun 10, 2019 1:57 pm

Re: I2C device responding on all addresses

Mon Jun 10, 2019 1:58 pm

It could be you have connected SDA to SCL and vice-versa

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