| Andrea Gelmini | 89140f4 | 2010-06-03 11:33:50 +0200 | [diff] [blame] | 1 | The I2C protocol knows about two kinds of device addresses: normal 7 bit |
| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2 | addresses, and an extended set of 10 bit addresses. The sets of addresses |
| 3 | do not intersect: the 7 bit address 0x10 is not the same as the 10 bit |
| Jean Delvare | cbb4451 | 2011-11-23 11:33:07 +0100 | [diff] [blame^] | 4 | address 0x10 (though a single device could respond to both of them). |
| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5 | |
| Jean Delvare | cbb4451 | 2011-11-23 11:33:07 +0100 | [diff] [blame^] | 6 | I2C messages to and from 10-bit address devices have a different format. |
| 7 | See the I2C specification for the details. |
| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 8 | |
| Jean Delvare | cbb4451 | 2011-11-23 11:33:07 +0100 | [diff] [blame^] | 9 | The current 10 bit address support is minimal. It should work, however |
| 10 | you can expect some problems along the way: |
| 11 | * Not all bus drivers support 10-bit addresses. Some don't because the |
| 12 | hardware doesn't support them (SMBus doesn't require 10-bit address |
| 13 | support for example), some don't because nobody bothered adding the |
| 14 | code (or it's there but not working properly.) Software implementation |
| 15 | (i2c-algo-bit) is known to work. |
| 16 | * Some optional features do not support 10-bit addresses. This is the |
| 17 | case of automatic detection and instantiation of devices by their, |
| 18 | drivers, for example. |
| 19 | * Many user-space packages (for example i2c-tools) lack support for |
| 20 | 10-bit addresses. |
| 21 | |
| 22 | Note that 10-bit address devices are still pretty rare, so the limitations |
| 23 | listed above could stay for a long time, maybe even forever if nobody |
| 24 | needs them to be fixed. |