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6
RS232 Modem Signals
Just as a telephony modem has control and status lines, the blu
also provides for 6 control and status lines as per the table below. The
direction column is as seen from the modules viewpoint.
Direction
IN or OUT
IN or OUT
IN
OUT
IN
OUT
The first four lines are under program control and as such require GPIO
pins and they are mapped to I/O as per the table below. The last two are
under control of the UART driver and their functionality is always
enabled.
PIO
Direction
Pin
0
IN/OUT
1
IN/OUT
2
IN/OUT
3
IN/OUT
4
IN
5
IN/OUT
6
IN/OUT
7
IN/OUT
Notes:
1
PIO4 (DSR) is used by the blu
connected, and is intricately linked with connections. For outgoing calls,
if this line is not asserted then an error is immediately. Similarly for
AT+BTP and AT+BTG.
While in a call, for appropriate modes, a deassertion means fall into
command state. If the deassertion exists for longer than the period
Function
CI also known as RI (Ring Indicate)
DCD (Data Carrier Detect)
DSR (Data Set ready)
DTR (Data Terminal Ready)
CTS (Clear to Send)
RTS (Request to Send)
Connector Pin Label
GPIO1
GPIO2
UART_RI
UART_DCD
UART_DSR
GPIO3/UART_DTR
GPIO4
GPIO5
2i
module to sense that the host is
24 of 36
Function
General Purpose I/O
General Purpose I/O
Input/Output from module
Input/Output from module
Input to Module
General Purpose I/O (or
DTR functionality)
General Purpose I/O
(Right LED)
General Purpose I/O (Left
LED)
2i
Module
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