Laird BL654 - nAutoRUN Pin and Operating Modes

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If the BL654 on the development board is powered from 1.8V supply, then you must use the 1.8V version of the FTDI USB-
UART cable. UART signal levels always need to match the supply voltage net VDD_nRF_SW of the BL654 development
board.
Figure 11: J1 wiring to match FTDI USB-UART cable (TTL-232R-3V3 cable)
Fit a jumper in J35 (to switch the Analog switch U15 and route BL654 UART to J1) when connecting an external FTDI USB-
UART TTL (3.3V) converter cable using J1.
Fitting a jumper in J35 also allows the BL654 UART to be routed to Atmel MCU UART (signal also on J19 and net names
beginning with IMCU_) via open solder bridges SB16 to SB19 shown in Figure 12. You must connect these bridges with
solder. This may be useful for those customers wanting to work with the Nordic SDK.
Figure 12: Open solder-bridges on the UART interface running from Atmel MCU (U4) to analog switch U15 (to BL654 ultimately)
On the development board, the USB_DTR output (FTDI chip U10) from the PC is wired to BL654 module pin SIO_35 (pin 5)
which is the nAutoRUN pin.
Note: smartBASIC runtime engine FW checks for the status of nAutoRUN during power-up or reset. The nAutoRUN pin
detects if the BL654 module should power up into Interactive/Development Mode (3.3 V) or Self-contained Run
mode (0V). The module enters Self-contained Run mode if the nAutoRUN pin is at 0V and an application called
$autorun$ exists in the module’s file system, then the smartBASIC runtime engine FW executes the smartBASIC
application script automatically; hence the name Self-contained Run mode.
SIO_06
R1
NOPOP (0R)
Module pin BL654 UART Data Flow
SIO_06 Module_TX Output
SIO_08 Module_RX Input
SIO_05 Module_RTS Output
SIO_07 Module_CTS Input
SIO_07
SIO_08
VDD_VSRC_nRF
SIO_05
FTDI (USB to TTL 232 Cable)
GND
USB_CTS
VCC
USB_TX
USB_RX
USB_RTS
GND
RTS
VCC
RX
TX
CTS
J1
NOPOP (PIN HEADER,2.54mm 1X6P)
1
1
2
2
3
3
4
4
5
5
6
6
GND
IMCU_RTS_A
IMCU_RxD_A
SB19NOPOP (Solderbridge_Open)
1
1
2
2
IMCU_TxD_A
IMCU_RTS
IMCU_CTS
IMCU_TxD
IMCU_RxD
SB16NOPOP (Solderbridge_Open)
1
1
2
2
IMCU_CTS_A
SB17NOPOP (Solderbridge_Open)
1
1
2
2
SB18NOPOP (Solderbridge_Open)
1
1
2
2