AP_Scripting: example saving serial data to SD card

libraries/AP_Scripting/examples/Serial_Dump.lua

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+-- this script reads data from a serial port and dumps it to a file
+local file_name = 'raw serial dump.txt'
+local file_name_plain = 'serial dump.txt'
+local baud_rate = 9600
+
+-- find the serial first (0) scripting serial port instance
+-- SERIALx_PROTOCOL 28
+local port = assert(serial:find_serial(0),"Could not find Scripting Serial Port")
+
+-- make a file
+local file = assert(io.open(file_name, "w"),"Could not create file " .. file_name)
+file = assert(io.open(file_name_plain, "w"),"Could not create file " .. file_name)
+file:close()
+
+-- begin the serial port
+port:begin(baud_rate)
+port:set_flow_control(0)
+
+function update() -- this is the loop which periodically runs
+
+  local n_bytes = port:available()
+  while n_bytes > 0 do
+    -- only read a max of 515 bytes in a go
+    -- this limits memory consumption
+    local buffer = {} -- table to buffer data
+    local bytes_target = n_bytes - math.min(n_bytes, 512)
+    while n_bytes > bytes_target do
+      table.insert(buffer,port:read())
+      n_bytes = n_bytes - 1
+    end
+
+    -- write as decoded
+    file = io.open(file_name, "a")
+    file:write(table.concat(buffer,',') .. '\n')
+    file:close()
+
+    -- write as plain text
+    file = io.open(file_name_plain, "a")
+    file:write(string.char(table.unpack(buffer)))
+    file:close()
+
+  end
+
+  return update, 1000 -- reschedules the loop
+end
+
+return update() -- run immediately before starting to reschedule