I2C communication
in [Embedded]
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From: Vladimir Vassilevsky on 22 Apr 2010 11:51 Andrew Smallshaw wrote: > On 2010-04-21, Vladimir Vassilevsky <nospam(a)nowhere.com> wrote: > >>Done quite complicated systems with I2C shared in multitask OS. Never >>had a need to analyse the bus. There is no point to do that: if you have >>control of the master, you know what is going on. > > > Which is fine until you have a multi master bus, That great attention paid to multi master I2C thing always surprised me. Had anyone ever seen a system with multiple masters on I2C in reality? > or you are not > entirely sure your master is working as intended - e.g. it is being > bit-banged. If one can't implement such a trivial thing like I2C master bit banging so to be entirely confident in it, he is not fit for embedded. > Debugging and analysis tools are completely pointless > if you know exactly what is going on - you have no need even for > a voltmeter if you are able to compute accurately what the voltage > at a given point will be in a given situation. However it often > helps to be able to measure things since your assumptions about a > system are not always correct. Sure, I don't have an I2C analyser > here and I've always managed to get by without one, but that doesn't > mean I seen times when one would have been useful. I verify the code with LEDs, scope and control printouts; never had any need for fancy debug tools. Best debug is not making techical mistakes at first time. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
From: Vladimir Vassilevsky on 21 Apr 2010 04:20 Neil wrote: > On 4/20/2010 1:38 PM, Vladimir Vassilevsky wrote: > >> >> >> rc_rcf wrote: >> >>> Hi, I am new to I2C bus. >> >> >> No, you not. You, my friend, are very, very stupid. >> >>> I need your help in letting me know how i can monitor >>> data through a I2C Data bus? I found a few products online like >>> AArdvark, >>> Beagle I2C protocol analyzer. I need product tht is Linux compatible. >> >> >> Emulate I2C by bit banging through PC LPT port. Emulation of master is >> trivial, slave is little bit more tricky. >> >>> Moreover, i also need it to monitor as well as allow me to inject some >>> data(sniffing). If you know of any such products please let me know. >>> Could i use aardvark and wireshark in order to fulfil my requiremnts? >>> Will wireshark capture I2C data and help me inject data through it as >>> well??If so any specific plugin required for wireshark? >> >> >> Idiot >> >>> what product will allow me to monitor I2C data as well as inject some >>> data(sniffing)? >> >> >> First and foremost: I2C is simple thing and there is absolutely no need >> to analyse it (unless you do reverse engineering). >> >> VLV >> > 1) Bit banging an Ic2 Slave on a PC Printer port is a bit more than > tricky. It is tricky bit banging a slave on a micro No problem. You only have to load old good DOS. > 2)I2C is simple if you are talking to an EEPROM. On a busy bus an > Analyzer can be quite handy. Done quite complicated systems with I2C shared in multitask OS. Never had a need to analyse the bus. There is no point to do that: if you have control of the master, you know what is going on. > MCC makes them also MCC-US.com VLV
From: Neil on 25 Apr 2010 13:45
On 4/22/2010 11:51 AM, Vladimir Vassilevsky wrote: > > > Andrew Smallshaw wrote: > >> On 2010-04-21, Vladimir Vassilevsky <nospam(a)nowhere.com> wrote: >> >>> Done quite complicated systems with I2C shared in multitask OS. Never >>> had a need to analyse the bus. There is no point to do that: if you >>> have control of the master, you know what is going on. >> >> >> Which is fine until you have a multi master bus, > > That great attention paid to multi master I2C thing always surprised me. > Had anyone ever seen a system with multiple masters on I2C in reality? Yes SMBus Batteries are MultiMaster. > >> or you are not >> entirely sure your master is working as intended - e.g. it is being >> bit-banged. > > If one can't implement such a trivial thing like I2C master bit banging > so to be entirely confident in it, he is not fit for embedded. Try Coding the master and slaves at the same time. There is only so much you can see on a DSO. > >> Debugging and analysis tools are completely pointless >> if you know exactly what is going on - you have no need even for >> a voltmeter if you are able to compute accurately what the voltage >> at a given point will be in a given situation. However it often >> helps to be able to measure things since your assumptions about a >> system are not always correct. Sure, I don't have an I2C analyser >> here and I've always managed to get by without one, but that doesn't >> mean I seen times when one would have been useful. > > I verify the code with LEDs, scope and control printouts; never had any > need for fancy debug tools. Best debug is not making techical mistakes > at first time. Normal I agree. But I had the monitor, ( from a former job where there was finger pointing) I used it, it saved me time. > > Vladimir Vassilevsky > DSP and Mixed Signal Design Consultant > http://www.abvolt.com |