UM10741
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User manual
Rev. 1 — 1 April 2014
25 of 61
NXP Semiconductors
UM10741
Fm+ development kit OM13320
5.4 Bus two (Bus2)
The second I
2
C bus on the Fm+ Development Board (OM13260) requires the addition of
an NXP LPC Xpresso Module (not included in the kit) to either be the Master, or drive the
bus controller (PCA9665, IC4).
There are two almost identical I
2
C buses on the Fm+ Development Board (OM13260),
called Bus1 and Bus2. These share a ground and power connection, but may be operated
independently.
Remark:
The bus voltage for each I
2
C maybe different (for example 3.3 V for one I
2
C bus,
5 V for the other I
2
C bus).
5.4.1 Bus2 master (LPC Xpresso — MCU LPC1343)
The LPC Xpresso Module contains an NXP LPC1343 MCU (similar to the one on Bus 1)
and support circuits called LPC-Link. See
Figure 26
. The LPC Xpresso requires firmware
that is loaded through either the LPC-Link and USB Bridge, or JTAG Single Wire Debug
(SWD) connector.
Remark:
The LPC Xpresso is not compatible with the NXP GUI, and requires the
installation of an IDE for code development.
The LPC-Link may be powered from the Fm+ Development Board (OM13260), or from a
USB Host (connected to the LPC-Link port). There is a possible conflict that the LCP-Link
3.3 V supply will compete with the Fm+ Development Board (OM13260) 3.3 V supply.
To avoid this issue the LPC Xpresso Module can provide its own 3.3 V power by removing
jumper JP1 on the Fm+ Development Board (OM13260). See
Figure 27
.
I
2
C Bus2 is connected to the MCU Port0 via RC edge rate control networks that provide
bus fall time control (SCL2: R45 and C23; SDA1: R44 and C19). See
Figure 28
.
Fig 26. Fm+ development board with LPC Xpresso installed