MCU-Link is also connected to the Flexcomm 1 (I2C) port of the target MCU through an I2C repeater / a voltage translator U27,
which enables communication between MCU-Link and the target MCU, by shifting voltage levels of signals between the two
devices from 3.3 V to 3.3/1.9 V and vice versa.
To use MCU-Link as a USB-to-SPI or USB-to-I2C bridge, the board must be connected to the host computer through a USB cable
from its J1 connector. A USB-to-SPI bridge can be used to program the target MCU using the ISP mode and/or to emulate the host
system. A USB-to-I2C bridge can be used to program the target MCU using the ISP mode and/or to emulate the host system /
board peripherals. NXP MCUXpresso Secure Provisioning Tool (SEC) provides an option to program the target via a USB-to-SPI
or USB-to-I2C bridge (see
The USBSIO feature can be disabled for SPI or I2C so that the target MCU SPI/I2C port can be used for other purposes. Disabling
this feature instructs the firmware not to enumerate the USB endpoint for USBSIO (which is called “MCU-Link LPCSIO” for
backward compatibility reasons). Disabling the USBSIO feature also frees more USB bandwidth for the SWO profiling and energy
measurement features of MCU-Link.
The USBSIO feature can be disabled for SPI by disabling voltage translator U24 (setting it to high impedance). To disable U24,
unpower the LPC55S36-EVK board and short jumper JP57 (not populated on the board). Shorting/opening JP57 after powering
up the board has no impact on the functions/features of the MCU-Link firmware. When USBSIO feature is disabled for SPI, then
the target MCU SPI port can be used for other purposes.
The USBSIO feature can be disabled for I2C by opening jumper JP4.
3.7 Connecting to a target through a USB-to-GPIO bridge
The MCU-Link USBSIO feature also allows MCU-Link to be used as a USB-to-GPIO bridge to connect the MCU-Link LPC55S69
target to the host computer. Support for the USBSIO feature can be enabled on the host computer using the libusbsio library,
which is a free host library from NXP for Windows/Linux/MacOS systems. For more details on the libusbsio library, see
The USB-to-GPIO bridge can be used to control a limited number of GPIO pins of LPC55S69. The LPC55S36-EVK board supports
a 1x6 pin GPIO header J133 (not populated on the board) for accessing these GPIO pins on the board. The table below lists
the LPC55S69 GPIO pins that can be controlled through USB-to-GPIO bridge and shows how these pins are mapped to GPIO
header pins.
Table 26. USB GPIO pin assignments
LPC55S69 pin
GPIO header J133 pin
Signal direction
PIO1_1
Pin 1
Output from MCU-Link
PIO1_9
Pin 2
Output from MCU-Link
PIO1_20
Pin 3
Input to MCU-Link
PIO1_21
Pin 4
Output from MCU-Link
PIO1_31
Pin 3
Output from MCU-Link
PIO1_7
Pin 6
Input to MCU-Link
3.8 Measuring target MCU power consumption
The LPC55S36-EVK board supports measurement of total current drawn (MCU_VCC_3V3_1V9) by the target MCU (LPC5536)
through onboard MCU-Link. The MCU-Link can measure the total current and power of the MCU_VCC_3V3_1V9 supply without
requiring any additional equipment. The LPC55S36-EVK current measurement circuit is enabled by default (resistor R432 is DNP
by default). For current measurement, the supported voltage range is 1.7 V – 3.6 V.
The measurement hardware automatically selects either a low or high range current to provide higher accuracy at low currents.
Automatic range switching from low current drawn to high current drawn avoids excessive voltage drop across the sense
NXP Semiconductors
MCU-Link Debug Probe
LPC55S36-EVK Board User Manual, Rev. 1, 24 January 2022
User Manual
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