Difference between revisions of "I2C Bus"
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Revision as of 22:53, 15 November 2010
Registers
| NAME | ADDRESS | WIDTH |
|---|---|---|
| REG_I2CDATA | 0x04004500 | 1 |
| REG_I2CCNT | 0x04004501 | 1 |
REG_I2CDATA
| BIT | DESCRIPTION |
|---|---|
| 0 | R/W, clear for write, set for read |
| 1 | Start/device select bit? |
| 2 | Restart/device reselect bit? |
| 3 | ? |
| 4 | SCL hold. When clear SCL is being held low, set when SCL is high. This bit must always be set(by reading CNT again) after writing REG_I2CCNT. This bit must be set when writing blocks of data(more than 1 byte) with bit0 clear. |
| 5 | SCL, toggle this for each loop iteration(in the loop execute the I2C WR code) with max 8 iterations where the loop exits successfully when bit 4 is set. This bit must be set when writing blocks of data(more than 1 byte) with bit0 clear. |
| 6 | Unknown, always set when writing to CNT? |
| 7 | Enable/busy, wait for this bit to clear after writing to I2CCNT. |
Protocol
Wait for the busy bit to clear. Write the device address to REG_I2CDATA, then write 0xc2(busy/enable, bit 6, and start bit 1 set) to REG_I2CCNT. Execute swiWaitByLoop for a device-specific duration, then write the register address to REG_I2CDATA, and write 0xc0 to REG_I2CCNT.(busy/enable and bit 6 set) Wait with swiWaitByLoop device duration, then write the data to REG_I2CDATA when writing. When reading, write the device address to REG_I2CDATA and write 0xc2 to REG_I2CCNT. When the delay value is zero, write 0xc1 | i<<5 to REG_I2CCNT, otherwise write 0xc0 | i<<5 to REG_I2CCNT, wait for busy to clear, delay, then write 0xc5 to REG_I2CCNT. For writing i is the loop i for iteration, for reading replace that with 1. When reading, read the data from REG_I2CCNT. Return a error if REG_I2CCNT bit 4 SCL hold is set, otherwise return normal.
I2C devices
I2C device table:
| Device index in table | Device address | Device swiWaitByLoop delay | Device description |
|---|---|---|---|
| 0 | 0x00 | 0x00 | Camera0? |
| 1 | 0x80 | 0x00 | Camera1? |
| 2 | 0x00 | 0x00 | ? |
| 3 | 0x00 | 0x00 | ? |
| 4 | 0x7A | 0x180 | Power management |
| 5 | 0x78 | 0x00 | ? |
| 6 | 0xA0 | 0x00 | ? |
Power management
When registers 0x70 and 0x11 are set to 1 in that order, a power cycle is done.
| REGISTER | WIDTH | DESCRIPTION |
|---|---|---|
| 0x11 | 1 | System reset register 2. |
| 0x12 | 1 | Might be MMC bus power related, unknown. |
| 0x31 | 1 | Cameras' power? Value 0 turns off power to cameras? Values 1/2 activates a camera's power? |
| 0x70 | 1 | System reset register 1. |