This example shows how to create a connection to a serial device, write data to the device, and read data from the device.
Caution
Excessive voltage and current can damage the BeagleBone Black hardware. Observe the
manufacturer precautions for handling the BeagleBone Black hardware and connecting it to
other devices. For more information, see the local copy of the BeagleBone drivers and
documentation in the BeagleBone Black Getting Started
folder on your host
computer, or https://beagleboard.org/Support/Hardware%20Support.
Create a connection to the BeagleBone Black hardware.
bbb = beaglebone;
Show the location of the Tx and Rx pins on the GPIO header.
showAllPins(bbb)
Connect the BeagleBone Black hardware to a +3.3V
serial
device.
BeagleBone Black hardware uses +3.3V
. Do
not connect BeagleBone Black hardware directly to devices that use
higher voltages.
To receive data, connect the P9_26 (UART1_RXD)
pin
on the BeagleBone Black hardware to the TxD pin on the serial device.
To transmit data, connect the P9_24 (UART1_TXD)
pin
on the BeagleBone Black hardware to the RxD pin on the serial device.
Connect a ground pin, GND
, on the
BeagleBone Black hardware to the GND
pin on the
serial device.
Connect a +3.3V
pin on the BeagleBone
Black hardware to the VCC
pin on the serial device.
Restart the BeagleBone Black hardware. After the hardware
restarts, you can use serialdev
to exchange data
with serial devices.
Before continuing, research the manufacturer product information to determine which baud rate, data bits, parity, and stop bit settings the serial device supports.
Use enableSerialPort
to reconfigure
GPIO pins P9_26
and P9_24
as UART1_RXD
and UART1_TXD
.
enableSerialPort(bbb, 1) bbb.AvailableSerialPorts
ans = '/dev/ttyO1'
In '/dev/ttyO1'
, the 'O'
is
the capital letter O
, not the number zero.
Use serialdev
to create a connection
to the serial device and assign the connection to a object.
serial = beaglebone.serialdev(bbb,'/dev/ttyO1')
serial = serialdev with properties: BaudRate: 115200 DataBits: 8 Parity: 'none' StopBits: 1 Timeout: 10
In this example, the connection uses the default values
for baud rate (115200
), data bits (8
),
parity ('none'
), and stop bit (1
).
If the serial device requires nondefault values, use a set of optional arguments to override those defaults.
serial = beaglebone.serialdev(bbb,'/dev/ttyO1',115200,8,'none',2)
serialdev with properties: Port: '/dev/ttyO1' BaudRate: 115200 DataBits: 8 Parity: 'none' StopBits: 1 Timeout: 10
This example overrides the default value of StopBits
by
setting it to 2
. The other arguments maintain the
correct sequence of arguments to the left of the rightmost overriding
value.
You can write values to the serial device.
write(serial,[10 12],'uint16')
In this example, you write two values to the serial device.
The values override the default precision, uint8
,
by setting it to uint16
.
You can also read an array of values from the serial port.
output = read(serial,100)
This example reads a 100-element array of uint8
values
from the serial device.
If the serial connection times out during read operations,
you can adjust the time out period by assigning a new value to the Timeout
property.
serial.Timeout = 20
serialdev with properties: Port: '/dev/ttyO1' BaudRate: 115200 DataBits: 8 Parity: 'none' StopBits: 1 Timeout: 20
When you are finished using the serial interface, restart the hardware to make additional GPIO pins available.