TWR-K20D72M User’s Manual
Page 9 of 17
Note: there are no ETM signals on K20D72M, so the associated signals on Cortex Debugger connector
is left empty.
2.5
USB Interface
TWR-K20D72M board allows using USB as host or device in standalone mode or with connection to
TWR-SER board in a complete tower kit. Jumper J16 can be used to select which USB VBUS signal from
USB connector to connect with the MCU VREGIN input pin. When using in standalone mode, short 5-6
on J16 and connect USB with on board Micro-USB connector J19, when using with TWR-SER board in
complete tower kit, short 6-8 on J16 and connect USB with Mini-AB connector J14 on TWR-SER board.
Refer to description on J16 in Table 4 “TWR-K20D72M Jumper Table” for more information.
2.6
Infrared Port
An infrared transmit and receive interface is implemented as shown in Figure 4 below. The CMT_IRO
pin directly drives an infrared diode. The receiver uses an infrared phototransistor connected to an on-
chip analog comparator through a low-pass filter.
Figure 4: Infrared Port Implementation
2.7
External Bus Interface – FlexBus
The K20 device features a multi-function external bus interface called the FlexBus interface controller,
capable of interfacing to slave-only devices. The FlexBus interface is not used directly on the TWR-
K20D72M. Instead, a subset of the FlexBus is connected to the Primary Connector so that the external
bus can access devices on Tower peripheral modules. Refer to Table 6 “TWR-K20D72M Primary
Connector Pinout“and sheet 8 of the2.8
Accelerometer
An MMA8451Q digital accelerometer is connected to the K20 MCU through an I2C interface and a
GPIO/IRQ signal. Refer to Table 5 “I/O Connectors and Pin Usage Table” for connection details.
2.9
Potentiometer, Pushbuttons, LEDs
The TWR-K20D72M features two pushbutton switches connected to GPIO/interrupt signals, one
pushbutton connected to the master reset signal, two capacitive touch pad electrodes, four user-
