Accessing the bus directly
Now, as for a USB bus, we should take a look at how we can get direct access to the I2C bus. In the same manner, as for USB devices, if one of them doesn't have a dedicated driver, they can be managed directly from the user space. The only problem that may arise is if the I2C device generates interrupts; in this case, we cannot manage these signals from the user-space and a kernel driver must be used. However, this is a rare case and the presented technique can be used in most cases.
For example, we're going to manage the DAC chip named TC1321. If we take a look at the chip's datasheet, we can see that its functioning is very simple: it has one 16-bit register at offset 0x00, where we can write the digital data to be converted.
Tip
The datasheet is available at the URL http://ww1.microchip.com/downloads/en/DeviceDoc/21387C.pdf.
The register has the following format:
|
Data register = first byte |
Data register = second byte | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
D9 |
D8 |
D7 |
D6 |
D5 |
D4 |
D3 |
D2 |
D1 |
D0 |
- | ... | ||||
