BT900-Sx Hardware Integration Guide
Intelligent BTv4.0 Dual Mode Module
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5.6
SPI Bus
The SPI interface is an alternate function on SIO pins, configurable by
smart
BASIC.
The module is a master device that uses terminals SPI_MOSI, SPI_MISO, and SPI_CLK. SPI_CSB is implemented
using any spare SIO digital output pins to allow for multi-dropping.
The SPI interface enables full duplex synchronous communication between devices. It supports a 3-wire
(SPI_MOSI, SPI_MISO, SPI_SCK,) bi-directional bus with fast data transfers to and from multiple slaves.
Individual chip select signals are necessary for each of the slave devices attached to a bus, but control of
these is left to the application through use of SIO signals. I/O data is double buffered.
The SPI peripheral supports SPI mode 0, 1, 2, and 3.
Table 12: Peripheral supports
Signal Name
Pin No
I/O
Comments
SPI_MOSI
8
O
This interface is an alternate function configurable by
smart
BASIC. Default in the FW pin 8 and 10 are inputs.
SPIOPEN() in smart BASIC selects SPI function and changes pin 8
and 10 to outputs (when in SPI master mode).
SPI_MISO
7
I
SPI_CLK
10
O
5.7
I2C Interface
The I2C interface is an alternate function on SIO pins, configurable by
smart
BASIC command.
The two-wire interface can interface a bi-directional wired-OR bus with two lines (SCL, SDA) and has
master/slave topology. The interface is capable of clock stretching. Data rates of 100 kbps and 400 kbps are
supported.
An I2C interface allows multiple masters and slaves to communicate over a shared wired-OR type bus
consisting of two lines which normally sit at VCC. The BT900 module can only be configured as an I2C
master and can be the only master on the bus. The SCL is the clock line which is always sourced by the
master; the SDA is a bi-directional data line which can be driven by any device on the bus.
IMPORTANT: It is essential to remember that pull-up resistors on both SCL and SDA lines are not provided
in the module and MUST be provided external to the module.
Table 13: I2C Interface
Signal Name
Pin #
I/O
Comments
I2C_SDA
11
I/O
This interface is an alternate function on each pin, configurable
by
smart
BASIC. I2COPEN() in
smart
BASIC selects I2C function.
I2C_SCL
12
I/O
5.8
General Purpose I/O, ADC, PWM/FREQ and Host-wakeup
5.8.1
GPIO
The 18 SIO pins are configurable by
smart
BASIC and can be accessed individually. Each has the following user
configured features:
Input/output direction (output drive strength – 4mA).
For inputs, Internal pull up resistors (33K typical) or no pull-up.
5.8.2
ADC
The ADC is an alternate function on SIO pins and is configurable by
smart
BASIC.
