AP_Scripting: add CAN read and write examples

libraries/AP_Scripting/examples/CAN_read.lua

@@ -0,0 +1,20 @@
+-- This script is an example of reading from the CAN bus
+
+-- Load CAN driver, using the scripting protocol and with a buffer size of 5
+local driver = CAN.get_device(5)
+
+function update()
+
+  -- Read a message from the buffer
+  frame = driver:read_frame()
+
+  if frame then
+    -- note that we have to be careful to keep the ID as a uint32_t userdata to retain precision
+    gcs:send_text(0,string.format("CAN msg from " .. tostring(frame:id()) .. ": %i, %i, %i, %i, %i, %i, %i, %i", frame:data(0), frame:data(1), frame:data(2), frame:data(3), frame:data(4), frame:data(5), frame:data(6), frame:data(7)))
+  end
+
+  return update, 100
+
+end
+
+return update()

libraries/AP_Scripting/examples/CAN_write.lua

@@ -0,0 +1,74 @@
+-- This script is an example of writing to CAN bus
+
+-- Load CAN driver, using the scripting protocol and with a buffer size of 5
+local driver = CAN.get_device(5)
+
+-- transfer ID of the message were sending
+local Transfer_ID = 0
+
+-- RGB colours in 0 - 255 range, and RGB fade speed
+local red = 255
+local green = 0
+local blue  = 0
+local fade_speed = 5
+
+
+function update()
+
+  -- send UAVCAN Light command
+  -- uavcan.equipment.indication.LightsCommand
+  -- note that as we don't do dynamic node allocation, the target light device must have a static node ID
+
+  msg = CANFrame()
+
+  -- extended frame, priority 30, message ID 1081 and node ID 11
+  -- lua cannot handle numbers so large, so we have to use uint32_t userdata
+  msg:id( (uint32_t(1) << 31) | (uint32_t(30) << 24) | (uint32_t(1081) << 8) | uint32_t(11) )
+
+  msg:data(0,0) -- set light_id = 0
+
+  -- convert colors to 565 rgb
+  local red_5bit   = red >> 3
+  local green_6bit = green >> 2
+  local blue_5bit  = blue >> 3
+
+  -- first is made up of 5 bits red and 3 bits of green
+  msg:data(1, (red_5bit << 3) | (green_6bit >> 3))
+
+  -- remaining 3 bits of green and 5 of blue
+  msg:data(2, ((green_6bit << 5) | blue_5bit) & 0xFF)
+
+  -- Tail includes, start of transfer, end of transfer, toggle and transfer ID bits.
+  msg:data(3, (1 << 7) | (1 << 6) | Transfer_ID)
+
+  Transfer_ID = Transfer_ID + 1
+  -- transfer ID is 5 bits
+  if Transfer_ID > 31 then
+    Transfer_ID = 0
+  end
+
+  -- sending 4 bytes of data
+  msg:dlc(4)
+
+  -- write the frame with a 10000us timeout
+  driver:write_frame(msg, 10000)
+
+  -- basic RGB fade
+  if red > 0 and blue == 0 then
+    red = red - fade_speed
+    green = green + fade_speed
+  end
+  if green > 0 and red == 0 then
+    green = green - fade_speed
+    blue = blue + fade_speed
+  end
+  if blue > 0 and green == 0 then
+    red = red + fade_speed
+    blue = blue - fade_speed
+  end
+
+  return update, 100
+
+end
+
+return update()