S42
Hardware User Guide
1VV0301303 Rev. 11
Page 24 of 85
2021-05-06
Not Subject to NDA
If UICP is deactivated the pull-down resistor on UART-CTS# helps to keep the serial
interface active if UART-CTS# is open.
If UICP is active and the serial interface is down, UART-CTS# must be held at VCC and
thus the pull-down would cause an unwanted permanent current drain. Therefore, the
pull-down is switched off in this mode.
3.3.6.
Additional I/O Signals for Serial Interface Functionality
If CEN firmware is used see [3], S42/Central AT Command Reference,
80512ST10771A, for the configuration possibilities of additional signals support further
function for the serial interface. For other firmware version refer to the specific at
command reference.
3.3.6.1.
Hang-up via GPIO Signal
When using the CEN firmware and applications, call control can be supported by GPIO[4].
Driving GPIO[4] to logic High lev
el during a data transfer phase will “hang up” the
connection and disconnect the Bluetooth link. This signal may be mapped to DSR if an
RS232-style (DTE-type) interface is used. Please refer to
for a functional specification.
GPIO[4] can be left unconnected if this feature is not used.
3.3.6.2.
GPIO’S
IO [A, B, C, D]
When using the CEN firmware these GPIO’s may be configured via AT commands to add
further functionality to the serial interface.
Signal
Optional Function
Comment
IOA
DEVICEREADY#
Low active signal indicating that the
initialization has been finished and the
device is ready to process commands after
start-up
IOB
CONNECTED#
Low active signal indicating that a CEN
connection to a remote peer has been
established (DCD like)
IOC
TBD
Reserved for future use
IOD
TBD
Reserved for future use
3.4.
GPIO Interface
It is possible to use the programmable digital I/Os GPIO[0:14] on the S42. Their
behavior must be defined project specific in the firmware used.
Unused GPIO pins shall be left unconnected to stay compatible. There may be functions
assigned to some in future versions of the firmware.
