RELEASE
Revision B1
©Serious Integrated, Inc.
27
Some chemicals including (but not limited to) Ketone-based products, harsh cleansers, and abrasive cleaning products
can discolor and/or damage the PET film. To ensure long usable lifetime, make sure end-users are well-informed on how
to clean and maintain the touch screen.
The SIM535 employs a stand-alone 4-wire resistive
Semtech SX8656
touch controller with proximity sensing. The
SX8656 provides sophisticated touch sensing/processing and delivers touch data back to the MCU via I2C. When touch
data is available (for example, when the screen is pressed or a finger is dragged along the touch panel), the touch
controller generates an interrupt on an MCU interrupt pin at which point software can read the device and determine
the pixel coordinates and/or action.
See the
I2C Device Summary
for the complete table of I2C device addresses.
See the
Interrupt Summary
for the complete table of external peripheral interrupts.
The
Serious Human Interface™ Platform
has integrated touch drivers and algorithms that automatically map touch
coordinates to GUI objects.
PROXIMITY SENSING
Most standard SIM535 variants include the SX8656 with proximity sensing capabilities which senses the presence of
objects, like a bare finger, that alter a projected capacitive field above the touch screen surface. This enables, for
example, software to “automatically” brighten the LCD backlight when a finger approaches the screen. This proximity
sensing is a binary capability – the signal indicates either a finger is “near” or “not near”, but does not indicate any
relative positioning or indication of distance.
AMBIENT LIGHT SENSING
Some variants of the SIM535 include an Ambient Light Sensor (“ALS”), the
Avago APDS-9002-021
or similar. Since the
backlight on the SIM535’s LCD display can be very bright, especially in low ambient light environments, software may
want to modulate the backlight brightness to improve readability as well as backlight LED longevity. The ALS is
connected to an MCU analog input (
PH3/AN3-ALS
) and the ambient light intensity can be derived from the ADC value.
HAPTIC FEEDBACK
Some custom variants of the SIM535 include a Haptic Feedback feature. When this feature is implemented, the
Semtech SX8656 is replaced by the SX8654 (which adds the haptic driver capability) and a haptic motor is populated on
the module.
Note the power consumption and heat issues related to haptic motor drive circuitry; see the Semtech data sheet for more
information.
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