One of the many useful TI-BASIC commands that you discover very quickly is the simple wait. We take it for granted without often appreciating its value - enter a command, then wait(2) and there is a satisfying 2 second pause before the next command is carried out.
Lua has no such in-built command, although one is readily created in a variety of ways. However, as I quickly discovered, a key difference between TI-BASIC programming and Lua scripting is the element of multi-tasking. This is not supported on the handheld, and hence in TI-BASIC, which means that the simple wait command can work just as you would expect it to: command is issued, wait for a given time, and then proceed to the next.
In Lua however, capable of multi-tasking, if you try this process you quickly discover that the first command is issued, then your wait command is issued - but while this is being carried out, the script happily continues to fulfil subsequent commands. These things can happen simultaneously.
Now overall, of course, such multi-tasking is a great advantage. Suppose you are using a TI-BASIC program to collect some data from a sensor attached to your Innovator Hub. Obviously, it would be nice to see that data as it is being collected - perhaps even see the graph unfold?
Unfortunately, this is not possible. Without multi-tasking capabilities, the handheld (or computer or iPad) running TI-BASIC will not show you any such changes until it finishes what it was working on! So the data will be happily captured and stored, as requested, but you will not see this on Calculator, or spreadsheet or graph screen until the collection process is complete. Frustrating.
This points to a key advantage of controlling your Innovator Hub using Lua - such processes are easily achieved. Properly scripted, your data can be collected and displayed at the same time. Likewise, if you are displaying changes on screen from the effects of some Innovator Hub activity, these can be shown live.
What is not so simple within Lua is to go backwards and recreate that simple sequencing that TI-BASIC delivers freely - and for that, we use a special tool called a oneShotTimer.
The oneShotTimer effectively hijacks the Lua script timer for its own purposes: the timer is linked to a period, and a function. The period will be the length of time that you wish the related function to run for. The function will be specific to the task that you wish to achieve while waiting.
Before we examine these elements in detail, we should first check on those changes to the script which are required here. Once again, the script is essentially the same as those we have studied previously, with just a few additions for the purposes of learning more about this oneShotTimer. These are highlighted in red in the script snippets on the right, and below.
We add a new variable to those previously used (timeStr - to display information from the timer).
Two lists (index and dataList) are created to store accumulated values of numeric results - this is now possible with a timer function, and offers a powerful advantage of using Lua over TI-BASIC. The lists are stored as TI-Nspire variables and so may be viewed (live) in graph or spreadsheet.
You will notice in the menu that we have amalgamated the two sample menus from the previous lessons (SET Samples and READ Samples) and added a third, specific to this lesson - TIMER Samples.
The three functions in the TIMER Samples menu will form the basis for this tutorial.
In addition to displaying both rxValue and message lines, we have added a timerStr line to display information about the timer as it does its work. We also define initial values for the variables in on.resize.
Here is where the action happens! Three sample functions are provided for you to study.
wait(input)
This is a fairly generic oneShotTimer() function, deliberately styled after the TI-BASIC form - so we call, say, wait(5) and would like the process to pause for 5 seconds and then continue.
Looking ahead into the function, find where the oneShotTimer is called, and look at its arguments: oneShotTimer(1000*time_step,wait) . The first calls a 1 second delay (or whatever your time_step is set to), and then the wait function is called again - but this time WITHOUT any input! This is important - it accepts a delay period only the first time it is called.
This explains the first line of the function: we have set up a delay variable already, and the first time the wait function is called, the input is stored as delay, from which it may be accessed later. So for wait(5), on the first run, delay is set to the value 5. A time_step value is set - use 1 for 1 second intervals, but be careful when using smaller intervals as the read function needs time to gather and send data. Hence you will see an adjustment which forces a read only at 1 second intervals.
While delay is greater than or equal to zero, the timeStr is displayed, the current hubStrOn command is run, and the oneShotTimer function is called. This serves to start the clock, a second passes (or whatever your time_step is set to), delay is decreased, and the wait function is called again. This happens each second until time catches up with the delay value, and then it stops.
The nice feature of this function is that it takes whatever is the current hubStrOn command - SET LIGHT ON, or play sound, or run servo - and adds a 5 second timer. Try reading BRIGHTNESS to set that as the current command. Then run wait(5) and you will see values read at 1 second intervals for 5 seconds, as specified.
blink(rep,waitValue)
Again, styled after a simple TI-BASIC function, this takes a value for number of blinks ('rep') and delay between blinks ('waitValue').
As previously, we link these to existing defined variables (repeats and delay) so that the first time the function is run, these variables are defined with the values desired. So, for example, blink(5,0.5) will blink 5 times at half second intervals.
I defined another variable called "lightState" for this function, since I want to know whether the light is ON or OFF, and switch between these values each time the function is run.
The sequence of this function is similar to the wait function above, although this time it is the variable 'repeats' that serves as the count down, rather than 'delay' (which stays constant and serves the same role as time_step did previously.) This time, though, we step through TWICE the number of steps specified, so that we can turn the light ON and then OFF for each repetition.
alarm(rep,waitValue)
Just to add a little variety, this function is a variation on blink to demonstrate how the same principle can be applied in different ways.
No changes from that previously defined.
These functions are as previously defined.
-- TI Innovator Init Values
platform.apilevel = '2.7'
local screen = platform.window
local date = "021517"
local isASIavailable = false local hubStrOn, hubStrOff, msgStr, rxValue, timeStr, delay, repeats
local index, dataList = {}, {}
var.store("index", index)
var.store("dataList", dataList)
function addMsg(input)
msgStr = input
print(msgStr)
screen:invalidate()
end
function on.construction()
--the next three lines are required for Hub connection
TI_Innovator.init(TI_InnovatorStateCallback)
TI_Innovator.setReadListener(TI_InnovatorReadCallback)
TI_Innovator.connect()
TI_Innovator.Send(hubStrOn) -- This is an example of sending a SET command to the Hub
TI_Innovator.Read() -- This is an example of sending a READ command to the Hub
screen:invalidate()
function str2list(input, def)
local list = {}
if input:find(def) then
list = input:split(def)
table.foreachi(list,print)
else
list = {input}
end
return list
end
function TI_InnovatorReadCallback(port, error_msg) -- this is the callback function that is defined above and catches the result of a READ command send to the Hub.
rxValue = port:getValue() or '' -- this gets the actual return value from the hub and puts it in the variable rxValue. The user may choose any variable name and also may do any calibration or ranging of the value here. Note that rxValue may be numeric, list or string (hence the utility function list2str) if tonumber(rxValue) then rxValue = math.floor(100*rxValue+0.5)/100
else rxValue = tostring(rxValue) rxValue = str2list(rxValue,string.char(10))[1] end
addMsg(hubStrOn)
if tonumber(rxValue) then voltage = (rxValue/2^14)*3.3 end -- an example of converting a raw 14 bit ADC value into voltage.
screen:invalidate()
end
function TI_InnovatorStateCallback(event)
addMsg("TI_InnovatorStateCallback")
if 'ready' == event then
TI_InnovatorConfig()
elseif "disconnected" == event then
-- user may choose to do some clean up or display a msg when the Hub is disconnected.
addMsg("TI_Innovator Hub disconnected")
end
screen:invalidate()
end
function TI_InnovatorConfig() -- this function is called from TI_InnovatorStateCallback() when a ready connection is succesful.
-- place CONNECT and other Hub startup commands here
addMsg("TI_Innovator Hub connected")
end
function wait(input)
if input then delay = input end
time_step = 0.1
if delay >= 0 then
timeStr = "Wait Time: "..delay.." seconds"
delay = math.floor((1/time_step)*(delay - time_step)+0.5)*time_step
TI_Innovator.Send(hubStrOn)
if hubStrOn:find("READ") then TI_Innovator.Read() end
if tonumber(rxValue) then -- This allows our wait function to serve as a timed data collection tool
local ct = currentTimer
if currentTimer == nil then
timerStop()
end
if currentTimer.oneShot then
currentTimer = nil
timerStop()
end
ct.listenerHandler(unpack(ct.params))
screen:invalidate()
end
-- oneShotTimer ENDS
-- TI Innovator BEGINS
TI_Innovator = { }
function TI_Innovator.init(theStateCallback)
if not pcall(function() require 'asi' end) then
addMsg('Hub NOT available')
return
end
addMsg('Hub available')
isASIavailable = true
local HANDSHAKE_GREETING = 'ISTI\n'
local HANDSHAKE_ANSWER = 'TISTEM'
local portFoundList = { }
local state
local handshakeState
local notifyEvent
local asiStateListener
local startScanning
local stopScanning
local portFoundListener
local portStateListener
local handshake_SendListener
local handshake_readListener
local handshake_port
local TI_Innovator_port
local baudRate = asi.BAUD_RATE_DEFAULT
local readTimeout = asi.READ_TIMEOUT_DEFAULT
-- User callbacks
local stateCallback = theStateCallback
local SendCallback
local readCallback
function notifyEvent(event)
addMsg('notifying '.. event)
if stateCallback then
-- Configure port for normal use
TI_Innovator_port = reportedPort
TI_Innovator_port:setReadTimeout(readTimeout)
TI_Innovator.setWriteListener(SendCallback)
TI_Innovator.setReadListener(readCallback)
-- Notify launchpad is ready
notifyEvent('ready')
end
local result = TI_Innovator_port:write(data .. '\n')
if result then addMsg(tostring(data)..': '.. tostring(result))
else addMsg(tostring(data)) end
return result
end
function TI_Innovator.Read(bytes_to_read)
if not TI_Innovator_port then
return "No TI Hub attached"
end
return TI_Innovator_port:read(bytes_to_read)
end
function TI_Innovator.request(request)
if not TI_Innovator_port then
return "No TI Hub attached"
end
local result = TI_Innovator_port:write(request .. '\n')
if result then addMsg(tostring(request) .. ': '.. tostring(result))
else addMsg(tostring(request)) end
result = TI_Innovator_port:read()
addMsg('read() '.. tostring(result))
if result then
local isASIavailable = false local hubStrOn, hubStrOff, msgStr, rxValue, timeStr, delay, repeats
local index, dataList = {}, {}
var.store("index", index)
var.store("dataList", dataList)
function addMsg(input)
msgStr = input
print(msgStr)
screen:invalidate()
end
function on.construction()
--the next three lines are required for Hub connection
TI_Innovator.init(TI_InnovatorStateCallback)
TI_Innovator.setReadListener(TI_InnovatorReadCallback)
TI_Innovator.connect()
TI_Innovator.Send(hubStrOn) -- This is an example of sending a SET command to the Hub
TI_Innovator.Read() -- This is an example of sending a READ command to the Hub
screen:invalidate()
function str2list(input, def)
local list = {}
if input:find(def) then
list = input:split(def)
table.foreachi(list,print)
else
list = {input}
end
return list
end
function TI_InnovatorReadCallback(port, error_msg) -- this is the callback function that is defined above and catches the result of a READ command send to the Hub.
rxValue = port:getValue() or '' -- this gets the actual return value from the hub and puts it in the variable rxValue. The user may choose any variable name and also may do any calibration or ranging of the value here. Note that rxValue may be numeric, list or string (hence the utility function list2str) if tonumber(rxValue) then rxValue = math.floor(100*rxValue+0.5)/100
else rxValue = tostring(rxValue) rxValue = str2list(rxValue,string.char(10))[1] end
addMsg(hubStrOn)
if tonumber(rxValue) then voltage = (rxValue/2^14)*3.3 end -- an example of converting a raw 14 bit ADC value into voltage.
screen:invalidate()
end
function TI_InnovatorStateCallback(event)
addMsg("TI_InnovatorStateCallback")
if 'ready' == event then
TI_InnovatorConfig()
elseif "disconnected" == event then
-- user may choose to do some clean up or display a msg when the Hub is disconnected.
addMsg("TI_Innovator Hub disconnected")
end
screen:invalidate()
end
function TI_InnovatorConfig() -- this function is called from TI_InnovatorStateCallback() when a ready connection is succesful.
-- place CONNECT and other Hub startup commands here
addMsg("TI_Innovator Hub connected")
end
function wait(input)
if input then delay = input end
time_step = 0.1
if delay >= 0 then
timeStr = "Wait Time: "..delay.." seconds"
delay = math.floor((1/time_step)*(delay - time_step)+0.5)*time_step
TI_Innovator.Send(hubStrOn)
if hubStrOn:find("READ") then TI_Innovator.Read() end
if tonumber(rxValue) then -- This allows our wait function to serve as a timed data collection tool
local ct = currentTimer
if currentTimer == nil then
timerStop()
end
if currentTimer.oneShot then
currentTimer = nil
timerStop()
end
ct.listenerHandler(unpack(ct.params))
screen:invalidate()
end
-- oneShotTimer ENDS
-- TI Innovator BEGINS
TI_Innovator = { }
function TI_Innovator.init(theStateCallback)
if not pcall(function() require 'asi' end) then
addMsg('Hub NOT available')
return
end
addMsg('Hub available')
isASIavailable = true
local HANDSHAKE_GREETING = 'ISTI\n'
local HANDSHAKE_ANSWER = 'TISTEM'
local portFoundList = { }
local state
local handshakeState
local notifyEvent
local asiStateListener
local startScanning
local stopScanning
local portFoundListener
local portStateListener
local handshake_SendListener
local handshake_readListener
local handshake_port
local TI_Innovator_port
local baudRate = asi.BAUD_RATE_DEFAULT
local readTimeout = asi.READ_TIMEOUT_DEFAULT
-- User callbacks
local stateCallback = theStateCallback
local SendCallback
local readCallback
function notifyEvent(event)
addMsg('notifying '.. event)
if stateCallback then
-- Configure port for normal use
TI_Innovator_port = reportedPort
TI_Innovator_port:setReadTimeout(readTimeout)
TI_Innovator.setWriteListener(SendCallback)
TI_Innovator.setReadListener(readCallback)
-- Notify launchpad is ready
notifyEvent('ready')
end
local result = TI_Innovator_port:write(data .. '\n')
if result then addMsg(tostring(data)..': '.. tostring(result))
else addMsg(tostring(data)) end
return result
end
function TI_Innovator.Read(bytes_to_read)
if not TI_Innovator_port then
return "No TI Hub attached"
end
return TI_Innovator_port:read(bytes_to_read)
end
function TI_Innovator.request(request)
if not TI_Innovator_port then
return "No TI Hub attached"
end
local result = TI_Innovator_port:write(request .. '\n')
if result then addMsg(tostring(request) .. ': '.. tostring(result))
else addMsg(tostring(request)) end
result = TI_Innovator_port:read()
addMsg('read() '.. tostring(result))
if result then
