Laird BL654 - Four-wire UART Serial Interface; UART Mapping

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Table 3 displays the four signals running from Atmel MCU U14 (SWD interface plus SIO_32 and nReset_BLE) to the BL654
module (SWD interface plus SIO_32 and nReset_BLE).
Table 3: USB U4 USB-SWD to BL654 SWD signal routing connections
U4 (Atmel MCU) Net
SWD Interface into
Analog switch U24
USB cable plugged into USB2
(USB_DETECTp HIGH)
No USB cable plugged into USB2
(USB_DETECTp LOW)
Comments
Route SWD Interface from Atmel
MCU (U4) to BL654 Module
Net Name
Route SWD Interface from Atmel MCU
(U4) to JP1
OB_SWDCLK
SWDCLK_BLE (pin 3)
SWDCLK_EXT (JP1 pin4)
OB_SWDIO
SWDIO_BLE (pin 1)
SWDIO_EXT (JP1 pin2)
OB_RESET
nRESET_BLE (pin 19)
via R131 0R (Not populated)
nRESET_EXT (JP1 pin10)
OB_SWO
SIO_32 (pin 7)
SWO_EXT (JP1 pin6)
via SB21 open solderbridge
SIO_32 is a trace output (called SWO, Serial Wire Output) and is not necessary for programming BL654 over the SWD
interface.
nReset_BLE is not necessary for programming BL654 over the SWD interface.
The development board provides access to the BL654 module four-wire UART interface (TX, RX, CTS, RTS) either through
USB (via UT10 FTDI USB-UART convertor chip) or through a breakout header connector J1.
Note: The BL654 module provides four-wire UART interface on the HW and the other four signals (DTR, DSR, DCD, RI),
which are low bandwidth signals, can be implemented in a smartBASIC application using any spare digital SIO
pins.
The UART connection on the BL654 series module and the FTDI IC are shown in Table 4. Figure 10 explains how the BL654
series module UART is mapped to the breakout header connector J1. These connections are listed in Table 4.
Table 4: SIO/UART connections
BL654 (U5) SIO
BL654 Default Function
FTDI IC UART
SIO_06 (U5 pin35)
UART_TX (output)
USB_RX
SIO_08 (U5 pin29)
UART_RX (input)
USB_TX
SIO_05 (U5 pin39)
UART_RTS (output)
USB_CTS
SIO_07 (U5 pin37)
UART_CTS (input)
USB_RTS
Note: Additionally, SIO_35 (the nAutoRUN input pin on the module) can be driven by the USB_DTR output pin of the
FTDI chip. This allows testing the $autorun$ application on boot without setting the autorun jumper on the
development board. nAutorun can be controlled directly from Laird’s UWTerminalX using the DTR tick box.