VERSION 1.0
J20 (38223)
Initialization
The J20 rev1 requires a supply of 1.8V from the dev kit board. This has to be enabled first by writing to the
GPIO port expander on the dev kit board. Rev 2 of the J20 features an on-board 1.8V LDO, so the enabling of
the 1.8V supply is not required. Please run the following commands every time after powering up the system,
so that the J20 is initialized.
i2cset -f -y 1 0x77 3 0xfb
- enable 1.8V power to the J20 (rev 1 only)
i2cset -f -y 6 0x20 6 0x3e
- configure the outputs of the I2C port expander
(low byte) - clock lines remain input, so there
is no data collision
i2cset -f -y 6 0x20 7 0x33
- configure the outputs of the I2C port expander
(high byte)
i2cset -f -y 6 0x20 2 0xfe
- write ones to all GPIO outputs and turn on LED
(low byte)
i2cset -f -y 6 0x20 3 0xff
- write ones to all GPIO outputs
(high byte)
If the initialization commands above have been executed successfully the GPIO LED should be lighted up. The
power (PWR) LED should be always on. A Pi camera connected should respond to I2C accesses. We have tested
the port detection with i2cdetect. After init the GPIO port expander should show up on address 0x20 (device
6).
In the default configuration the J20 is configured that the
GPIO port expander only supplies the CAM_GPIO signal to
the CSI-2 connectors.
With the Raspberry Pi cameras the CAM_GPIO is the reset
to the camera. It must be inactive to allow the camera to
work.
The CAM_CLK by default is connected to the CAM_CLK
signals of the 120 pin dev kit connector. So R11, R12, R15,
R16, R17, and R18 are installed. 0R resistors (0603 size) or
solder jumpers.
Please make sure that the on-board GPIO expander is
configured correctly with the i2cset commands as listed
above. The clock pins must be configured as inputs. If not
then the port expander will drive against the clock signals
of the dev kit board. This potentially could cause a
hardware damage.
AUVIDEA GMBH
TECHNICAL REFERENCE MANUAL
5
