Bw tool
intro
The bw_tool is meant to provide a basic commandline access to the bitwizard expansion boards. It was written for the raspberry pi, but has now been proven to work on other Linux platforms with an spidev device as well.
basic example
The simplest invocation:
bw_tool -t "Hello World!"
will display the shown text on an SPI_LCD on the default SPI bus (SPI0). Options modify the defaults.
options
options specifying the device
The option
-I
will switch to I2C mode.
The option
-D <device>
will use that device. Specify /dev/spidev0.1 for the second SPI bus on the raspberry pi for example. Or /dev/i2c-1 to specify the second I2C bus. This second i2c bus is the one that is broken out on the gpio's of rev2 raspberry pi's.
The option
-a <address>
specifies the address of the device to use. Note that BitWizard uses the full 8 bits that are sent to the device. Add one for "read" operation. In some circles, notably I2C, it is customary to specify just those 7 bits. Thus when the I2C_LCD is at the default address of 0x82, i2cdetect will scan it at address 0x41.
options sending data
the option
-t "text"
will send the text to the device, at port zero. The port cannot be changed, but all BitWizard PCBs that have the option of displaying text have the text port at port zero.
The option
-w <addr>:<byte>
will write the byte to the port at addr. For LCD-equipped boards for example -w 12:50 will set the contrast to 0x50.
The option
-W <addr>:<short>
will write the 16-bit short to the port at addr. For example -W 81:1000 will write the value 0x1000 to the numsamples port on an analog-equipped board.
reading data
The option
-R <port>:<datasize>
reads the data at port from the device. Datasize can be 'b' for byte (default), 's' for short (16 bits), or 'i' for a 32-bit integer.
finer control
To test sending data to SPI devices, there is the
--hex [byte...]
option. This simply sends the bytes specified, and reports back what was received. Note that bitwizard boards will not send any data until they have been selected, so the first byte received will represent whatever static is found on the bus.