The handsfree (HF) driver in UEME is meant for the headset. In RM-25, the output is driven in fully differential
mode. In the fully differential mode, the HF pin is the negative output and the HFCM pin is the positive output.
The gain of the handsfree driver in the differential mode is 6 dB. The earpiece (EARP, EARN) and headset (HF,
HFCM) signals are multiplexed so that the outputs can not be used simultaneously. The HF and HFCM amplifiers
include a transient suppression circuitry, which prevents unwanted spikes in HF and HFCM outputs when
switching on and off the amplifiers.
The HeadInt line will be pulled up to 2.7V by the internal resistor when the accessory is connected. When not
having the accessory inserted the voltage in the HeadInt line will be <0.8 V caused by internal pull down resistor
in the HF line.
Camera interface
RM-25 has a digital camera with viewfinder function. The camera resolution is VGA (640 x 480 pixels) . The
camera module is connected by means of a soldered on connector to the PWB.
The camera interface is a serial CCP, which is an unidirectional interface; the control information to camera is
transmitted through I2C bus. The I2C bus is implemented purely by the SW using general purpose I/Os.
The CCP interface consists of differential clock and data signals. The CCP enables the use of high data rates with
low EMI; maximum transfer capacity is 104Mbit/s, which means that transferring YUV VGA(640 x 480) images
at 15fps is possible.
The camera needs two power sources, 2.8V for analog circuit voltage VDD and 1.8V for digital circuit voltage
VDDI. VDD is provided from same discrete regulator as LCD and VDDI is fed from UEME’s Vcore.
FM radio
FM radio circuitry is implemented using the highly integrated FM radio ASIC, TEA5767. The MCU SW controls the
FM radio circuitry through a proprietary 3-wire bus.
The stereo output is fed to the UEME via one of the microphone inputs, MIC3.
The antenna of the FM Radio is created with the headset. The wires of the headset are used as antenna.
The data bus on the radio will be disabled when not used, in order to save current (BUSENABLE).
The VAUX1 regulator of the UEME will power the FM radio at nominal 3V.
The reference clock for the FM radio is the SleepClk signal picked up through a resistive divider.
Flashing
SW download in service is implemented by custom tools and SW; kindly refer to
Mode sensing
The RM-25 has different operational modes depending on the positions of the top and bottom parts.
There are five switches to sense the mechanical position of the two parts. A cam disk in the swivel activates a
pair of switches, and three Hall switches activated by magnets sense the position of the hinge.
The actual phone mode is interpreted from the position sensors and the phone is controlled accordingly.
Testing interfaces
RM-25 has a testing interface that is easy to access by service battery. The following signals are allocated on
test pads.
RM-25
Nokia Customer Care
System module
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Company Confidential
9235618 (Issue 2)
Copyright ©2005 Nokia. All Rights Reserved.
