KIT34825EPEVME Evaluation Board
, Rev. 2.0
6
Freescale Semiconductor
Hardware Description
4
Hardware Description
The hardware in the evaluation kit includes an 34825 evaluation board and a standard USB A-to-B cable.
The evaluation board has three major blocks: the circuit related to the 34825, the remote control and
accessory simulator, and the USB-to-I2C interface. This section describes the above three blocks as well
as an example of an audio accessory with remote control.
4.1
34825 Circuit
The schematic related to the 34825 is shown in
. Jumpers are offered to configure the evaluation
board for demonstration or evaluation purposes. When the evaluation board is used to be directly jump
connected to a cell phone PCB, these jumpers should be disconnected to prevent interference between
the signals from the evaluation board and the cell phone board.
4.1.1
I2C and Interrupt Signals
The I2C signals are the interrupt signal are connected to the MCU. The transistors Q1 and Q2 are for
level shifting between the 5V I2C signal for the MCU and the VDDIO from the 34825. The jumpers J6, J7,
and J8 should normally be always connected unless the evaluation board is used to directly jump these
signals to a cell phone PCB, in which case the signals are jumped directly from the corresponding test
points TP3, TP4 and TP5 to the cell phone PCB and the above jumpers should be disconnected.
4.1.2
Audio Signals
The audio signals include the microphone (MIC) signal and the stereo speaker (SPK_L and SPK_R)
signals. These three signals are connected to the microphone and the stereo audio jacks.
4.1.3
UART Signals
The UART signals are connected to the MCU on the evaluation board via jumpers J16 and J17 as well
as transistors Q3 and Q4. The two transistors are for level shifting purpose. Since the UART features are
not enabled, users should keep the JP16 and JP17 open all the time. The UART feature can be evaluated
with the UART signals from a different circuit by jumping the signals to test points TP18 and TP19.
4.1.4
LED Indicators
The evaluation offers two LEDs to indicate the status of the two logic signals ISET and OUT. When a
power supply is attached to the mini-USB connector, depending on the type of the power supply, the ISET
output will indicate either high impedance open-drain output or low impedance to ground. The red LED
DS2 is used to indicate the ISET logic level. If the internal power MOSFET is turned on (refer to the
datasheet for more details), the voltage at the VBUS pin is switched to the OUT pin. The red LED DS1
will indicate the voltage level at the OUT pin. Jumpers J4 and J5 should always be connected for these
two signals. There are another two LEDs on the Evaluation Board DS3 and DS4. They are reserved for
Freescale internal use only. Please keep the jumpers J10 and J11 open all the time.
