UART Module¶
Since | Origin / Contributor | Maintainer | Source |
---|---|---|---|
2014-12-22 | Zeroday | Zeroday | uart.c |
The UART (Universal asynchronous receiver/transmitter) module allows configuration of and communication over the UART serial port.
The default setup for the console uart is controlled by build-time settings. The default uart for console is UART0
. The default rate is 115,200 bps. In addition, auto-baudrate detection is enabled for the first two minutes
after platform boot. This will cause a switch to the correct baud rate once a few characters are received. Auto-baudrate detection is disabled when uart.setup
is called.
For other uarts, you should call uart.setup
and uart.start
to get them working.
uart.on()¶
Sets the callback function to handle UART events.
Syntax¶
uart.on([id], method, [number/end_char], [function], [run_input])
Parameters¶
id
uart id, default value is uart num of the console.method
"data", data has been received on the UART. "error", error occurred on the UART.number/end_char
. Only for eventdata
.- if pass in a number n<255, the callback will called when n chars are received.
- if n=0, will receive every char in buffer.
- if pass in a one char string "c", the callback will called when "c" is encounterd, or max n=255 received.
function
callback function.- event "data" has a callback like this:
function(data) end
- event "error" has a callback like this:
function(err) end
.err
could be one of "out_of_memory", "break", "rx_error". run_input
0 or 1. Only for "data" event on console uart. If 0, input from UART will not go into Lua interpreter, can accept binary data. If 1, input from UART will go into Lua interpreter, and run.
To unregister the callback, provide only the "data" parameter.
Returns¶
nil
Example¶
-- when 4 chars is received.
uart.on("data", 4,
function(data)
print("receive from uart:", data)
if data=="quit" then
uart.on("data") -- unregister callback function
end
end, 0)
-- when '\r' is received.
uart.on("data", "\r",
function(data)
print("receive from uart:", data)
if data=="quit\r" then
uart.on("data") -- unregister callback function
end
end, 0)
-- uart 2
uart.on(2, "data", "\r",
function(data)
print("receive from uart:", data)
end)
-- error handler
uart.on(2, "error",
function(data)
print("error from uart:", data)
end)
uart.setup()¶
(Re-)configures the communication parameters of the UART.
Syntax¶
uart.setup(id, baud, databits, parity, stopbits, echo_or_pins)
Parameters¶
id
uart idbaud
one of 300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 74880, 115200, 230400, 256000, 460800, 921600, 1843200, 3686400databits
one of 5, 6, 7, 8parity
uart.PARITY_NONE
,uart.PARITY_ODD
, oruart.PARITY_EVEN
stopbits
uart.STOPBITS_1
,uart.STOPBITS_1_5
, oruart.STOPBITS_2
echo_or_pins
- for console uart, this should be a int. if 0, disable echo, otherwise enable echo
- for others, this is a table:
tx
int. TX pin. Requiredrx
int. RX pin. Requiredcts
in. CTS pin. Optionalrts
in. RTS pin. Optionaltx_inverse
boolean. Inverse TX pin. Default:false
rx_inverse
boolean. Inverse RX pin. Default:false
cts_inverse
boolean. Inverse CTS pin. Default:false
rts_inverse
boolean. Inverse RTS pin. Default:false
flow_control
int. Combination ofuart.FLOWCTRL_NONE
,uart.FLOWCTRL_CTS
,uart.FLOWCTRL_RTS
. Default:uart.FLOWCTRL_NONE
Returns¶
configured baud rate (number)
Example¶
-- configure for 9600, 8N1, with echo
uart.setup(0, 9600, 8, uart.PARITY_NONE, uart.STOPBITS_1, 1)
uart.setup(2, 115200, 8, uart.PARITY_NONE, uart.STOPBITS_1, {tx = 17, rx = 16})
uart.getconfig()¶
Returns the current configuration parameters of the UART.
Syntax¶
uart.getconfig(id)
Parameters¶
id
UART id (0 or 1).
Returns¶
Four values as follows:
baud
one of 300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 74880, 115200, 230400, 256000, 460800, 921600, 1843200, 3686400databits
one of 5, 6, 7, 8parity
uart.PARITY_NONE
,uart.PARITY_ODD
, oruart.PARITY_EVEN
stopbits
uart.STOPBITS_1
,uart.STOPBITS_1_5
, oruart.STOPBITS_2
Example¶
print (uart.getconfig(0))
-- prints 9600 8 0 1 for 9600, 8N1
uart.start()¶
Start the UART. You do not need to call start()
on the console uart.
Syntax¶
uart.start(id)
Parameters¶
id
uart id, except console uart
Returns¶
Boolean. true
if uart is started.
uart.stop()¶
Stop the UART. You should not call stop()
on the console uart.
Syntax¶
uart.stop(id)
Parameters¶
id
uart id, except console uart
Returns¶
nil
uart.setmode()¶
Set UART controllers communication mode
Syntax¶
uart.setmode(id, mode)
Parameters¶
id
uart idmode
value should be one ofuart.MODE_UART
default UART mode, is set after uart.setup() calluart.MODE_RS485_COLLISION_DETECT
receiver must be always enabled, transmitter is automatically switched using RTS pin, collision is detected by UART hardware (note: no event is generated on collision, limitation of esp-idf)uart.MODE_RS485_APP_CONTROL
receiver/transmitter control is left to the applicationuart.MODE_RS485_HALF_DUPLEX
receiver/transmitter are controlled by RTS pinuart.MODE_IRDA
Returns¶
nil
uart.txflush()¶
Wait for any data currently in the UART transmit buffers to be written out. It can be useful to call this immediately before a call to node.sleep()
because otherwise data might not get written until after wakeup.
Syntax¶
uart.txflush(id)
Parameters¶
id
uart id
Returns¶
nil
Example¶
print("I want this to show up now not in 5 seconds")
uart.txflush(0) -- assuming 0 is the console uart
node.sleep({secs=5})
See also¶
uart.wakeup()¶
Configure the light sleep wakeup threshold. This is the number of positive edges that must be seen on the UART RX pin before a light sleep wakeup will be triggered. The minimum value is 3. The default value is undefined, therefore you should always call this function before the first time you call node.sleep()
with the uart option set.
Syntax¶
uart.wakeup(id, val)
Parameters¶
id
uart idval
the new value
Returns¶
nil
Example¶
uart.wakeup(0, 5)
See also¶
uart.write()¶
Write string or byte to the UART.
Syntax¶
uart.write(id, data1 [, data2, ...])
Parameters¶
id
uart iddata1
... string or byte to send via UART
Returns¶
nil
Example¶
uart.write(0, "Hello, world\n")