Problem with multiple I2C devices in a bus...

Thanks for the reply again, Paul.

The address lines are hard-wired circuit traces.  I have confirmed correct 
addressing on all three of them.

BTW, are you aware (or have any experience with) any SOIC, dual channel, I2C 
programmable pots with non-volatile memory?  These Dallas devices are OK but 
they lose programming on power-down and I need to restore their values from 
PIC EEPROM on power-up.

Thanks.

Dave


"Paul Carpenter" <paul$@pcserv.demon.co.uk> wrote in message 
news:20050218.0921.306810snz@pcserv.demon.co.uk...
> On Thursday, in article <11195fvbv8h9l33@corp.supernews.com>
>     starfire151@cableone.net "starfire" wrote:
>>"Paul Carpenter" <paul$@pcserv.demon.co.uk> wrote in message
>>news:20050217.0937.306771snz@pcserv.demon.co.uk...
>>> On Wednesday, in article
>>>     <1117u2aiovrobdc@corp.supernews.com>
>>>     starfire151@cableone.net "starfire" wrote:
>>>>Hi all -
>>>>
>>>>Has anyone had any experience with using multiple I2C devices is a bus
>>>>architecture?
> ...
>>>>I am using a PIC18LF252 uC, a 24LC256 serial EEPROM, and three Dallas
>>>>DS1803
>>>>dual 100K programmable pots in a bus.  The circuit is on a printed 
>>>>circuit
>>>>board (not wire-wrapped or breadboarded).  The total length of SDA and 
>>>>SCL
>>>>lines is about 3 inches.
>>>
>>> Last time I used DS1803 I had four of them, plus several PCF8574 and
>>> PCF8591 off a PCF8584 controller on a H8.
>
> In other setups I have used I2C down 9 feet of twisted pair + shield 
> cable.
>
>>>>I'm using the CCS C compiler with built-in I2C functions for I2C start,
>>>>stop, write, and read.  I had to write my own routines to handle the
>>>>DS1803
>>>>device specifics.  I breadboarded a single DS1803 with some test code
>>>>using
>>>>the routines to verify correct operation.  It seemed to work well.  When 
>>>>I
>>>>put the three DS1803 chips in the circuit, along with the memory chip
>>>>though, it gives erratic results.
>>>
>>> The DS1803 is not too difficult to write for. Are you sure you are 
>>> putting
>>> the correct addresses out for all devices. Single unit has base address
>>> (0x50) however adding extra unit addresses tends to be where most people
>>> screw up on creating I2C addresses.
>>>
>>> What sub-addresses (unit numbers) are you using for the DS1803 devices?
>>>
>>>>I looked at the SDA and SCL on a logic analyzer and found out why it was
>>>>erratic.  Every other time I executed a read instruction, the SDA line
>>>>stayed low (did not output the stop condition).  The following command
>>>>fails
>>>>but resets the SDA line high again so the next instruction following 
>>>>works
>>>>again.  This repeats indefinitely.  Every other read works.  The write
>>>>cycles seem to be OK so I thought it must be timing related.  The DS1803
>>>>reads both pot values sequentially and I thought the data on the second
>>>>read
> ...
>>> The first thing I would check is that your are addressing the devices
>>> correctly as getting the addresses wrong in I2C causes a difference
>>> between  read and write mode.
> ...
>
>>Thanks for the reply, Paul.
>>
>>The addressing is correct for the three devices.  I've checked it several
>>times.  The device addresses that are flaky are the 000 and 001.  Address
>>010 seems to work fairly consistently.  I've confirmed the addressing with
>>the logic analyzer.
>
> There is of course the other thing, you have checked that all three
> address selection lines on ALL the DS1803 devices with a meter so that you
> have not got a floating input causing one device to be recognised at
> TWO addresses.
>
> On your breadboard setup if it still exists can you test a single device
> at the same addresses as your three device setup, to check the code for
> multiple devices.
>
>>I've downloaded the example you referred to from your web page and will
>>examine it.  I haven't had a chance to take a look at it yet.  I will
>>probably get a chance today or tomorrow.
>>
>>Thanks, again.
>>
>>Dave
>>
>
> -- 
> Paul Carpenter          | paul@pcserviceselectronics.co.uk
> <http://www.pcserviceselectronics.co.uk/>    PC Services
> <http://www.gnuh8.org.uk/>              GNU H8 & mailing list info
> <http://www.badweb.org.uk/>             For those web sites you hate
> 

Hi starfire,

> I don't think it differs from what I wrote earlier.  The condition is 
> consistent.  When monitoring the SDA and SCL lines, the initial condition 
> after power-up is that both lines are high (pulled up).  When I execute any 
> write instruction to any device on the bus, the final condition of the lines 
> are left both high again.  If I execute any read instruction to either the 
> pot at address 000 or the pot at address 001, the read completes 
> successfully (at least I see the data returned from the pots that was 
> programmed into them) but the status of lines is left with the clock line 
> high and the data line low. ...

That looks like my problem while expand some existing code, a few weeks 
ago. Are you sure, the master send a NAK after the last byte, he would 
read from the slave!? Otherwise, the next read/write operation to an 
other device will be impaired by _this_ slave. He is always in read mode!
In short: End Read Mode by sending NAK from the master!

> ... The next attempt at a read (or a write) fails 
> because the start condition is not sent on the bus.  At the end of the that 
> instruction, though, the data line is high again so the following 
> instruction is executed correctly again.  Reads to the pot at address 010 
> were OK and left the data line high.


Michael
-- 
Die eMail passt, und wer nicht spamt, kommt auch durch.
Gelesen wird jedoch nur ab und zu.

Please don't top post.

starfire wrote:
> "Wil Taphoorn" <wil@nogo.wtms.nl> wrote in message
> news:4215EC59.764798ED@nogo.wtms.nl...
> > starfire wrote:
> >
> >> The problem seems to be related to the data line not being shut off (left
> >> to
> >> be pulled back up to +5V after a complete transmission).
> >
> > This differs from what you wrote the first time:
> > | Every other time I executed a read instruction, the SDA line
> > | stayed low (did not output the stop condition).
> >
> 
> I don't think it differs from what I wrote earlier.  

Ok, I must have misread you then.

> The condition is consistent... [snipped]
...
> If I execute any read instruction to either the pot at address 000 or
> the pot at address 001, the read completes successfully (at least I
> see the data returned from the pots that was programmed into them) but
> the status of lines is left with the clock line high and the data line low.

Did you verify that the driver does a NAK on the final byte of that read? I
suggested you to check that in my initial reply.

If the master does ACK on the final byte then the slave reacts by putting it
first bit of a new data byte onto the SDA line. If that bit happens to be 0
then the master is unable to reclaim the bus. If, however, the master does a
NAK on the final byte the slave will close, thereby releasing both SDA and SCL.

-- 
Wil

On Friday, in article <111cuurpm51bce5@corp.supernews.com>
     starfire151@cableone.net "starfire" wrote:
As others have said please reply at the BOTTOM it is getting tiring
re jigging your posts..
>"Paul Carpenter" <paul$@pcserv.demon.co.uk> wrote in message 
>news:20050218.0921.306810snz@pcserv.demon.co.uk...
>> On Thursday, in article <11195fvbv8h9l33@corp.supernews.com>
>>     starfire151@cableone.net "starfire" wrote:
>>>"Paul Carpenter" <paul$@pcserv.demon.co.uk> wrote in message
>>>news:20050217.0937.306771snz@pcserv.demon.co.uk...
>>>> On Wednesday, in article
>>>>     <1117u2aiovrobdc@corp.supernews.com>
>>>>     starfire151@cableone.net "starfire" wrote:
>>>>>Hi all -
>>>>>
>>>>>Has anyone had any experience with using multiple I2C devices is a bus
>>>>>architecture?
>> ...
>>>>>I am using a PIC18LF252 uC, a 24LC256 serial EEPROM, and three Dallas
>>>>>DS1803
>>>>>dual 100K programmable pots in a bus.  The circuit is on a printed 
>>>>>circuit
....
>>>> Last time I used DS1803 I had four of them, plus several PCF8574 and
>>>> PCF8591 off a PCF8584 controller on a H8.
....
>>>> The first thing I would check is that your are addressing the devices
>>>> correctly as getting the addresses wrong in I2C causes a difference
>>>> between  read and write mode.
>> ...
>>
>>>Thanks for the reply, Paul.
>>>
>>>The addressing is correct for the three devices.  I've checked it several
>>>times.  The device addresses that are flaky are the 000 and 001.  Address
>>>010 seems to work fairly consistently.  I've confirmed the addressing with
>>>the logic analyzer.
>>
>> There is of course the other thing, you have checked that all three
>> address selection lines on ALL the DS1803 devices with a meter so that you
>> have not got a floating input causing one device to be recognised at
>> TWO addresses.
>>
>> On your breadboard setup if it still exists can you test a single device
>> at the same addresses as your three device setup, to check the code for
>> multiple devices.
...

>Thanks for the reply again, Paul.
>
>The address lines are hard-wired circuit traces.  I have confirmed correct 
>addressing on all three of them.

My issue was not the traces, but the quality of connections and shorts.
Have you checked your code against the breadboard with the breadboard
device at 000, 001 and 010.

>BTW, are you aware (or have any experience with) any SOIC, dual channel, I2C 
>programmable pots with non-volatile memory?  These Dallas devices are OK but 
>they lose programming on power-down and I need to restore their values from 
>PIC EEPROM on power-up.

In my application EEPROM was no use as the power unit had to reset, and a
startup sequence was needed, a saved value would set the wrong mode and smoke.
Without looking too hard I know that Dallas (now Maxim) and Xicor (now
Intersil) do parts with EEPROM.

A google search for "+EEPROM =pot" or "E2Pot" will turn up a lot of results.
  
The fact that Dallas/Maxim do parts with EEPROM and you had not found that
out worries me to how well you are looking at the problem as myself and others
have pointed out several items to check.

-- 
Paul Carpenter          | paul@pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/>    PC Services
<http://www.gnuh8.org.uk/>              GNU H8 & mailing list info
<http://www.badweb.org.uk/>             For those web sites you hate

"starfire" <starfire151@cableone.net> wrote in message 
news:1117u2aiovrobdc@corp.supernews.com...
> Hi all -
>
> Has anyone had any experience with using multiple I2C devices is a bus 
> architecture?


... snip ...



I just wanted to let everyone know I found the error of my ways.



The CCS compiler's i2c_read() instruction defaults to an acknowledge after 
each read request.  The Dallas DS1803 states it should receive no 
acknowledge on the last read data transfer.  There is a switch option in the 
CCS read instruction to force a "no ack" after the read, which I coded after 
the first read request.  Since the DS1803 did not see the "no ack" 
condition, it must have been fooled into thinking there would be another 
read request to follow.  The following command sends a bogus read request to 
an invalid address, resulting in a "no ack", which apparently satisfies the 
completion of the DS1803 cycle and it's ready for the next cycle.



I tried it again by forcing the ack after the first read and the no ack 
after the second read.  It worked perfectly.



Much thanks for all the responses.  You were all instrumental in helping to 
resolve this problem.  Once again this newsgroup has shown itself to be one 
of the most knowledgeable and responsive newsgroups on the net.



Thanks.



Dave

"Paul Carpenter" <paul$@pcserv.demon.co.uk> wrote in message 
news:20050219.1527.306859snz@pcserv.demon.co.uk...
> On Friday, in article <111cuurpm51bce5@corp.supernews.com>
>     starfire151@cableone.net "starfire" wrote:
> As others have said please reply at the BOTTOM it is getting tiring
> re jigging your posts..
>>"Paul Carpenter" <paul$@pcserv.demon.co.uk> wrote in message
>>news:20050218.0921.306810snz@pcserv.demon.co.uk...
>>> On Thursday, in article <11195fvbv8h9l33@corp.supernews.com>
>>>     starfire151@cableone.net "starfire" wrote:
>>>>"Paul Carpenter" <paul$@pcserv.demon.co.uk> wrote in message
>>>>news:20050217.0937.306771snz@pcserv.demon.co.uk...
>>>>> On Wednesday, in article
>>>>>     <1117u2aiovrobdc@corp.supernews.com>
>>>>>     starfire151@cableone.net "starfire" wrote:
>>>>>>Hi all -
>>>>>>
>>>>>>Has anyone had any experience with using multiple I2C devices is a bus
>>>>>>architecture?

...snip...

> In my application EEPROM was no use as the power unit had to reset, and a
> startup sequence was needed, a saved value would set the wrong mode and 
> smoke.
> Without looking too hard I know that Dallas (now Maxim) and Xicor (now
> Intersil) do parts with EEPROM.
>
> A google search for "+EEPROM =pot" or "E2Pot" will turn up a lot of 
> results.
>
> The fact that Dallas/Maxim do parts with EEPROM and you had not found that
> out worries me to how well you are looking at the problem as myself and 
> others
> have pointed out several items to check.
>
> -- 
> Paul Carpenter          | paul@pcserviceselectronics.co.uk
> <http://www.pcserviceselectronics.co.uk/>    PC Services
> <http://www.gnuh8.org.uk/>              GNU H8 & mailing list info
> <http://www.badweb.org.uk/>             For those web sites you hate

Paul -

Thanks for the resposne, again.

I have been trying everything that everyone has suggested to check.  That's 
how I ultimately found the answer (due to the no ack on the last read) to 
the problem.

I have checked Dallas/Maxim and Xicor for EEPROM pot parts but they don't 
make such parts with multiple addresses, dual devices, EEPROM, and I2C in an 
SOIC package, as was my original request.  I have also checked into the 
Xicor parts.  Ditto.

I have, in fact, done complete parametric searches on the Dallas/Maxim, 
Microchip, and Xicor sites.

The closest I've found is the Maxim MAX5479, which is in a different package 
style.  I'm putting my circuits together by hand (without using reflow 
ovens, etc.) so my package styles are necessarily somewhat limited.  I can't 
do ball grid arrays, for instance.

Thanks for the help.

Dave

On Saturday, in article <111f4oihcoli210@corp.supernews.com>
     starfire151@cableone.net "starfire" wrote:

....
>> In my application EEPROM was no use as the power unit had to reset, and a
>> startup sequence was needed, a saved value would set the wrong mode and 
>> smoke.
>> Without looking too hard I know that Dallas (now Maxim) and Xicor (now
>> Intersil) do parts with EEPROM.
>>
>> A google search for "+EEPROM =pot" or "E2Pot" will turn up a lot of 
>> results.
>>
>> The fact that Dallas/Maxim do parts with EEPROM and you had not found that
>> out worries me to how well you are looking at the problem as myself and 
>> others
>> have pointed out several items to check.
>>
>Paul -
>
>Thanks for the resposne, again.
...
>I have checked Dallas/Maxim and Xicor for EEPROM pot parts but they don't 
>make such parts with multiple addresses, dual devices, EEPROM, and I2C in an 
>SOIC package, as was my original request.  I have also checked into the 
>Xicor parts.  Ditto.

But it depends on what you mean by SOIC, as there are 150mil and 300mil
variants.

Most 14-20 pin TSSOP (173mil) packages are similar to SOIC 150mil.
 
>I have, in fact, done complete parametric searches on the Dallas/Maxim, 
>Microchip, and Xicor sites.

>The closest I've found is the Maxim MAX5479, which is in a different package

The package style is close enough to the SOIC 150ml (if not slightly larger)
Actually the DS1803 is also available in 14pin TSSOP
 
>style.  I'm putting my circuits together by hand (without using reflow 
>ovens, etc.) so my package styles are necessarily somewhat limited.  I can't 
>do ball grid arrays, for instance.

I do lots of boards by hand with SOT23-5 and even 144pin TQFP on 0.4mm pitch.
The TSSOP is slightly larger so probably easier to hand solder, also the pin
out probably makes isolation between load and micro easier.

You just have to be careful and an iron which can go don to 0.2mm tip helps
on reworking as well.

-- 
Paul Carpenter          | paul@pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/>    PC Services
<http://www.gnuh8.org.uk/>              GNU H8 & mailing list info
<http://www.badweb.org.uk/>             For those web sites you hate

"Paul Carpenter" <paul$@pcserv.demon.co.uk> wrote in message 
news:20050220.0055.306860snz@pcserv.demon.co.uk...
> On Saturday, in article <111f4oihcoli210@corp.supernews.com>
>     starfire151@cableone.net "starfire" wrote:
>

...snip...

> ...
>>I have checked Dallas/Maxim and Xicor for EEPROM pot parts but they don't
>>make such parts with multiple addresses, dual devices, EEPROM, and I2C in 
>>an
>>SOIC package, as was my original request.  I have also checked into the
>>Xicor parts.  Ditto.
>
> But it depends on what you mean by SOIC, as there are 150mil and 300mil
> variants.
>
> Most 14-20 pin TSSOP (173mil) packages are similar to SOIC 150mil.
>
>>I have, in fact, done complete parametric searches on the Dallas/Maxim,
>>Microchip, and Xicor sites.
>
>>The closest I've found is the Maxim MAX5479, which is in a different 
>>package
>
> The package style is close enough to the SOIC 150ml (if not slightly 
> larger)
> Actually the DS1803 is also available in 14pin TSSOP
>
>>style.  I'm putting my circuits together by hand (without using reflow
>>ovens, etc.) so my package styles are necessarily somewhat limited.  I 
>>can't
>>do ball grid arrays, for instance.
>
> I do lots of boards by hand with SOT23-5 and even 144pin TQFP on 0.4mm 
> pitch.
> The TSSOP is slightly larger so probably easier to hand solder, also the 
> pin
> out probably makes isolation between load and micro easier.
>
> You just have to be careful and an iron which can go don to 0.2mm tip 
> helps
> on reworking as well.
>
> -- 
> Paul Carpenter          | paul@pcserviceselectronics.co.uk
> <http://www.pcserviceselectronics.co.uk/>    PC Services
> <http://www.gnuh8.org.uk/>              GNU H8 & mailing list info
> <http://www.badweb.org.uk/>             For those web sites you hate
>

Actually, I've done connectors at 0.5mm pitch, also.  The tip of my standard 
Weller looked huge compared to the leads of the connector but being very 
careful, I managed to be successful.  That was only 16 pins.  I don't think 
I would attempt anything like a large flat pack without a much finer tip on 
my iron.  I've done a ton of SOT23 devices.  They're not a problem.

Have you found any way of doing BGAs by hand or is it flat impractical?

Dave

On Sunday, in article <111ha50214jn8be@corp.supernews.com>
     starfire151@cableone.net "starfire" wrote:

>"Paul Carpenter" <paul$@pcserv.demon.co.uk> wrote in message 
>news:20050220.0055.306860snz@pcserv.demon.co.uk...
>> On Saturday, in article <111f4oihcoli210@corp.supernews.com>
>>     starfire151@cableone.net "starfire" wrote:
...snip...

>>>The closest I've found is the Maxim MAX5479, which is in a different 
>>>package
>>
>> The package style is close enough to the SOIC 150ml (if not slightly 
>> larger)
>> Actually the DS1803 is also available in 14pin TSSOP
>>
>>>style.  I'm putting my circuits together by hand (without using reflow
>>>ovens, etc.) so my package styles are necessarily somewhat limited.  I 
>>>can't
>>>do ball grid arrays, for instance.
>>
>> I do lots of boards by hand with SOT23-5 and even 144pin TQFP on 0.4mm 
>> pitch.
>> The TSSOP is slightly larger so probably easier to hand solder, also the 
>> pin
>> out probably makes isolation between load and micro easier.
>>
>> You just have to be careful and an iron which can go don to 0.2mm tip 
>> helps
>> on reworking as well.
>>
>Actually, I've done connectors at 0.5mm pitch, also.  The tip of my standard 
>Weller looked huge compared to the leads of the connector but being very 
>careful, I managed to be successful.  That was only 16 pins.  I don't think 
>I would attempt anything like a large flat pack without a much finer tip on 

I use a Weller with 0.8mm tip and a JBC iron with interchangeable tips down
to conical 0.2mm. Also the JBC has temperature control and keeps the iron at
half temperature when the iron is on the stand, and heats to full temperature
in 2 seconds.

I find Elctrobe Flux pens useful for hand assembly/rework.

>my iron.  I've done a ton of SOT23 devices.  They're not a problem.

SOT23-5 are finer pitch 5 pin SOT23 devices (0.4mm pitch on one side),
basically 5 pins on a SOT23.

>Have you found any way of doing BGAs by hand or is it flat impractical?

Impractical to do any BGA by hand as you cannot check the joints properly
or be sure you you enough solder/flux on all pads to the same amount.
They need good reflow ovens to heat board and device at the same time.

-- 
Paul Carpenter          | paul@pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/>    PC Services
<http://www.gnuh8.org.uk/>              GNU H8 & mailing list info
<http://www.badweb.org.uk/>             For those web sites you hate

Thanks, Paul.

"Paul Carpenter" <paul$@pcserv.demon.co.uk> wrote in message 
news:20050220.1602.306873snz@pcserv.demon.co.uk...
> On Sunday, in article <111ha50214jn8be@corp.supernews.com>
>     starfire151@cableone.net "starfire" wrote:
>
>>"Paul Carpenter" <paul$@pcserv.demon.co.uk> wrote in message
>>news:20050220.0055.306860snz@pcserv.demon.co.uk...
>>> On Saturday, in article <111f4oihcoli210@corp.supernews.com>
>>>     starfire151@cableone.net "starfire" wrote:
> ...snip...
>
>>>>The closest I've found is the Maxim MAX5479, which is in a different
>>>>package
>>>
>>> The package style is close enough to the SOIC 150ml (if not slightly
>>> larger)
>>> Actually the DS1803 is also available in 14pin TSSOP
>>>
>>>>style.  I'm putting my circuits together by hand (without using reflow
>>>>ovens, etc.) so my package styles are necessarily somewhat limited.  I
>>>>can't
>>>>do ball grid arrays, for instance.
>>>
>>> I do lots of boards by hand with SOT23-5 and even 144pin TQFP on 0.4mm
>>> pitch.
>>> The TSSOP is slightly larger so probably easier to hand solder, also the
>>> pin
>>> out probably makes isolation between load and micro easier.
>>>
>>> You just have to be careful and an iron which can go don to 0.2mm tip
>>> helps
>>> on reworking as well.
>>>
>>Actually, I've done connectors at 0.5mm pitch, also.  The tip of my 
>>standard
>>Weller looked huge compared to the leads of the connector but being very
>>careful, I managed to be successful.  That was only 16 pins.  I don't 
>>think
>>I would attempt anything like a large flat pack without a much finer tip 
>>on
>
> I use a Weller with 0.8mm tip and a JBC iron with interchangeable tips 
> down
> to conical 0.2mm. Also the JBC has temperature control and keeps the iron 
> at
> half temperature when the iron is on the stand, and heats to full 
> temperature
> in 2 seconds.
>
> I find Elctrobe Flux pens useful for hand assembly/rework.
>
>>my iron.  I've done a ton of SOT23 devices.  They're not a problem.
>
> SOT23-5 are finer pitch 5 pin SOT23 devices (0.4mm pitch on one side),
> basically 5 pins on a SOT23.
>
>>Have you found any way of doing BGAs by hand or is it flat impractical?
>
> Impractical to do any BGA by hand as you cannot check the joints properly
> or be sure you you enough solder/flux on all pads to the same amount.
> They need good reflow ovens to heat board and device at the same time.
>
> -- 
> Paul Carpenter          | paul@pcserviceselectronics.co.uk
> <http://www.pcserviceselectronics.co.uk/>    PC Services
> <http://www.gnuh8.org.uk/>              GNU H8 & mailing list info
> <http://www.badweb.org.uk/>             For those web sites you hate
>