User's Manual

BT900-Sx Hardware Integration Guide
Intelligent BTv4.0 Dual Mode Module
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12 CONN-HIG-BT900
Note10: SPI CS is created by customer using any spare SIO pin within their smartBASIC
application script allowing multi-dropping.
Note11: SIO_TBD pin has to be pulled high externally to enable OTA (over the Air) smartBASIC
application download. Refer to the latest FW release documentation for details.
The BT900 module is delivered with the integrated smart BASIC runtime engine FW loaded (but no
onboard smartBASIC application script). Because of this, it starts up in AT command mode by
default.
At reset, all SIO lines are configured as the defaults shown above.
SIO lines can be configured through the smart BASIC application script to be either inputs or
outputs with pull-ups or none. When an alternative SIO function is selected (such as I2C or SPI),
the firmware does not allow the setup of internal pull-up. Therefore, when I2C interface is
selected, pull-up resistors on I2C SDA and I2C SCL MUST be connected externally as per I2C
standard.
All the SIO pins (with a default function of DIO are inputs – with no internal pull-up apart from
SIO_1 and SIO_3, which are outputs):
 SIO_1 (alternative function UART_TX) is an output, set high (in FW).
 SIO_2 (alternative function UART_RTS) is an output, set low (in FW).
 SIO_0 (alternative function UART_RX) is an input, set with internal weak pull-up (in FW).
 SIO_3 (alternative function UART_CTS) is an input, set with internal weak pull-down (in FW).
 SIO_7 is an input, set with internal pull-down (in FW). It is used for over the air downloading of
smart BASIC applications. Refer to the latest FW release documentation for details.
UART_RX, UART_TX, UART_CTS are 3.3 V level logic (if VCC is 3.3 V, i.e. SIO pin I/O levels track VCC).
For example, when RX and TX are idle, they sit at 3.3 V (if VCC is 3.3 V). Conversely, handshaking
pins CTS and RTS at 0 V are treated as assertions.
Pin 3 (nAutoRUN) is an input, with active low logic. In the development kit (DVK-BT900-sx) it is
connected so that the state is driven by the host’s DTR output line. The nAutoRUN pin must be
externally held high or low to select between the following two BT900 operating modes:
 Self-contained Run mode (nAutoRUN pin held at 0 V).
 Interactive / development mode (nAutoRUN pin held at VCC).
smartBASIC runtime engine firmware checks for the status of nAutoRUN during power-up or reset.
If it is low and if there is a smartBASIC application script named $autorun$, then the smartBASIC
runtime engine FW executes the application script automatically; hence the name
Self-contained Run Mode.
3.3 Electrical Specifications
3.3.1 Absolute Maximum ratings
Absolute maximum ratings for supply voltage and voltages on digital and analogue pins of the
module are listed below; exceeding these values causes permanent damage.
Table 3: Maximum Current Ratings
Parameter Min Max Unit
Voltage at
VCC
pin
-
0.3
+3.6
V
AVCC
VSS
-
0.5
VSS+4.6
V
AVREF
VSS
-
0.5
VSS+4.6
V
BT_VREG_IN_HV
2.3
4.8
V