Post by thread:[EE] I2C addressing

I've been Googling I2C all afternoon and have not found a solution to this problem. If the Microcontroller is the master doing software I2C using standard I/O ports (think 16F84) and you are connecting to a single slave device the addressing seems fairly straight forward. Great example here: http://tinyurl.com/ex8ul Full URL for the paranoid :) http://www.analog.com/UploadedFiles/Application_Notes/4357629173488053769440327090AN-561.pdf However, how does one handle multiple slave devices especially if they are the same device. In the example above, what if I need multiple AD7416s? How can they be addressed? Thank you

Nathan Nottingham wrote: > However, how does one handle multiple slave devices especially if they > are the same device. In the example above, what if I need multiple > AD7416s? How can they be addressed? Some slave chips have extra pins that let you select from a range of addresses. So if the device has 3 such pins you can put up to 8 of them on the same IIC bus. Check the data sheet of your device to see if and how many address pins it has. ****************************************************************** Embed Inc, Littleton Massachusetts, (978) 742-9014. #1 PIC consultant in 2004 program year. http://www.embedinc.com/products

On 11/4/05, Nathan Nottingham <spam_OUTnateTakeThisOuTnottingham-tech.com> wrote: > > However, how does one handle multiple slave devices especially if they > are the same device. In the example above, what if I need multiple > AD7416s? How can they be addressed? I'm sure I won't be the only to answer... but generally there are address bits that are configurable by connecting them to ground or supply voltage. In the diagram on pg 8 you'll see that they are all tied to ground, but you can get 2^3 combinations of addresses on that device by changing those inputs. Alex

Thank you and thanks to Olin as well. I'm a software programmer still thinking all problems can be solved in code. Alex Harford wrote: {Quote hidden}> On 11/4/05, Nathan Nottingham <.....nateKILLspam@spam@nottingham-tech.com> wrote: >> However, how does one handle multiple slave devices especially if they >> are the same device. In the example above, what if I need multiple >> AD7416s? How can they be addressed? > > I'm sure I won't be the only to answer... but generally there are > address bits that are configurable by connecting them to ground or > supply voltage. > > In the diagram on pg 8 you'll see that they are all tied to ground, > but you can get 2^3 combinations of addresses on that device by > changing those inputs. > > Alex >

Olin Lathrop writes: > Nathan Nottingham wrote: > > However, how does one handle multiple slave devices especially if they > > are the same device. In the example above, what if I need multiple > > AD7416s? How can they be addressed? > > Some slave chips have extra pins that let you select from a range of > addresses. So if the device has 3 such pins you can put up to 8 of them on > the same IIC bus. Check the data sheet of your device to see if and how > many address pins it has. And some come in N versions, with N different addresses (really an internal chip bonding option). See, for example, the Microchip 5 pin TO-220 I2C temperature sensors. Bill

> However, how does one handle multiple slave devices especially > if they are the same device As others have said, use the chip's address pins. A current project of mine has multiple F88 slaves, and I use a similar system so the user can configure it. Simply put (although there's more to it), each block of 8 x F88s has a base address and each F88 within that block has a unique address relative to the base address. Each block's base address can be changed with user-configurable jumpers, so that you are able to keep adding blocks of 8 x F88s

Nathan, what Olin said is correct. Slowly chewing the fish again... Each I2C device has permanent base address and sort of extension to it configurable by pins : individual device address. By setting ones and zeroes in different ways on the same type devices you want to put in parallel on I2C ( so two physical devices of the same type do not have the same "individual" address ) you will be able to access them independently through your software since each of them will have different ( in the "extra bits" field ) address. Otherwise you can't distinguish them in "software". Other solution is I2C extender. Go to Philips semiconductor website and search for I2C multiplexers / extenders ( don't recall correct name right now ) You will get an idea. WBR Dmitriy. Nathan Nottingham wrote: {Quote hidden}> > Thank you and thanks to Olin as well. I'm a software programmer still > thinking all problems can be solved in code. > > Alex Harford wrote: > > On 11/4/05, Nathan Nottingham <nateKILLspamnottingham-tech.com> wrote: > >> However, how does one handle multiple slave devices especially if they > >> are the same device. In the example above, what if I need multiple > >> AD7416s? How can they be addressed? > > > > I'm sure I won't be the only to answer... but generally there are > > address bits that are configurable by connecting them to ground or > > supply voltage. > > > > In the diagram on pg 8 you'll see that they are all tied to ground, > > but you can get 2^3 combinations of addresses on that device by > > changing those inputs. > > > > Alex > > > -

----- Original Message ----- From: "Jinx" {Quote hidden}> > However, how does one handle multiple slave devices especially > > if they are the same device > > As others have said, use the chip's address pins. A current project > of mine has multiple F88 slaves, and I use a similar system so the > user can configure it. Simply put (although there's more to it), each > block of 8 x F88s has a base address and each F88 within that > block has a unique address relative to the base address. Each block's > base address can be changed with user-configurable jumpers, so that > you are able to keep adding blocks of 8 x F88s I simply must know what it is that uses blocks of 8 x F88s. ;-) Is it some kind of LED sign control?

> I simply must know what it is that uses blocks of 8 x F88s. ;-) Is > it some kind of LED sign control? LEDs ? Oh, yawn ;-) No, it's a plug 'n' play PLC system. Not as dull as it sounds, each block is assigned a digital and/or analogue function(s). Not every F88 needs to be installed but its address range has to be reserved. Additionally, any F88 in the system has the capability of talking to any other. Although I've not implemented this, I've tested it and there are some intriguing possibilities, in the context of the application I'm sure this is just how CyberDyne Systems Corporation started ;-)) Hopefully I won't end up like Miles Bennett Dyson...........