RS485 signal collision

[Hadeel]

Dear admin,

I am running the code in the site, and I want to add 2 features....could you tell me how I do these?

1. Is there a way to execute port:write(':RR\r\n') every 60 sec even if port:read(17) does not return anything? As you said before, port:read(17) is blocking the script. If there's no response from the slave, the script is not going to be executed anymore 

2. I want to alart the system admin if there's no response from the slave(port:read(17)) for 5 min....can I do that in this script?

Code:

if not server then
  require('socket')
  server = socket.udp()
  server:setsockname('127.0.0.1', 5485)
  server:settimeout(60)
end

if not port then
  require('serial')
  port = serial.open('/dev/RS485-1', {
    baudrate = 19200,
    databits = 8,
    stopbits = 1,
    parity = 'none',
    duplex = 'half'
  })
end

data = server:receive()
if data then
  port:write(data)
  os.sleep(0.5)
end

port:flush()
port:write(':RR\r\n')
data, err = port:read(17, 1) -- read 17 bytes for up to 1 second
if data and #data == 17 then
  -- parse data response here
end