01-31-2016, 07:00 PM
(This post was last modified: 01-31-2016, 07:03 PM by MichaelMeissner.)
(01-31-2016, 05:43 PM)khgoh Wrote: For the I2C 4 wire connector, the pin are GND,SDA,SCL and 5V. For the five pin are GND, INTR, SDA, SCL and 5V. For some of the I2C device, they are build in with interrupt. With this interrupt, the CPU will have faster reaction time when certain condition is trigger. This also implied that if the CPU is waiting for the trigger condition, the CPU do not need to scan I2C device thus provide a more efficient use of I2C bus. 6 connectors ( 2pcs five pin and 4pcs of four pin I2C connector) is connect to TWI1-SCL/SDA channel in the pi-2 bus and another 6pcs of the connector is connected to TWI-SCL/SCA channel in the Pi-2 Bus.From a connector design point of view, I sort of wish you didn't have both 5 pin and 4 pin i2c items. For example, if you wanted to have both the ambient light sensor and a generic 4 pin i2c device share the same wire connection to the pine64, you would need to craft a 4 pin to 5 pin cable (and plug in the ambient light sensor first) to hook up the second device. Or you have to run a second i2c connection for the second item back to the board.
All of the INTR pin for the total of 4pcs of connector is connected to separate GPIO of the bus indicating on the PCB.
In addition, if you had moved the interrupt pin to one of the ends, you might be able to use a 4 pin connection (without the locking tabs) directly.
I would hope you plan to sell 5 pin and 4 pin connector cables in the pine64 store once you open for retail business, as well as the raw connectors.
If you had standardized on just having 5 pin cables, it would have made the interconnection simpler. But there is no standardization in this area.
Of the i2c devices I've looked at, the pinouts are all over the place, that I just give up and use separate wires.
