Mobile Phone Controlled Led Driver - A Tutorial

Mobile Phone Controlled Led Driver - OBSOLETE
See Andriod Controlled Led Driver instead

Note: The Btterm J2ME application used here does not appear to be available any more.
This page is for historical interest only and as an introduction to Andriod Controlled Led Driver using pfodApp which provides many more features then Btterm.



This tutorial extends the Bluetooth Controlled Led Driver
to a Mobile Phone Controlled Led Driver. This tutorial is also at http://www.forward.com.au/MobilePhoneControlledLedDriver/MobilePhoneControlledLedDriver.html
There are three parts to this tutorial,

Connecting your Mobile Phone to Bluetooth Controlled Led Driver

Enhancing the code to provide a more user friendly interface. (Posted)

Outline of the Tutorial

Introduction - Why add Mobile Phone Control
Choosing a Java enabled phone
Checking your existing phone
Loading Java Programs to your Phone
Running the BTTEST Java Program on your Phone
Connecting your Mobile Phone to the Bluetooth Controlled Led Driver
Finding the MAC address of your Bluetooth Module
Starting Bttest
Sending Commands to the Led Driver
Exiting the Terminal Program
Introduction - Why add Mobile Phone Control?

Mobile Phone control of your Led Driver offers a number of advantages

1. A suitable mobile phone provides an inexpensive remote control for your Led Lights.

When I had finished the Bluetooth Controlled Led Driver my first thought was building a remote control. That would have involved another uC, Bluetooth module, small box, push-buttons, batteries and ideally a LCD display and programming. Too much work, so I put off doing it. Then Georgi Bakalski contacted me about his Mobile Phone to bluetooth terminal application http://www.microcontroller-bg.com/btterm This inexpensive java module can be used to turn a suitable mobile phone in to a remote control for your Led Drive. This tutorial describes how to do this.

2. A mobile phone can provide a user friendly interface for setting the various modes available in your torch.

Modern flash lights now come with a wide variety of modes and operational settings, that require flow charts and detailed instructions to access and set. (See Programmable Light User Guides and Flowcharts) The instructions are along the lines of (with a little exaggeration) "Press the switch twice, then start whistling Dixie and on the third bar press the switch again for two bars. The flash light will flash twice (or not) then press the switch x times to set the time-out, etc." Using this Mobile Phone controlled Led Driver you can give the users easy access to all the operational modes and settings of the torch via prompts sent from the torch and displayed on the phone

3.The alpha numeric display on the phone allows you to display information about the state of you torch.

As well as allowing easy setting of the torch modes, the phone can also display the current state of the torch, such as the level of battery charge and count down the time before the torch will auto switch off.

4.Using your mobile phone remote you can add additional functionality to the torch.

Simple useful additional functionally, such as turning the torch on from the phone when you have dropped it in the dark, is available using the software presented here, as is using your phone to control the LED room lighting to set the right mood. Other functionally can be provided with some more programming in the Led Driver. For example, a number of flash lights have a setting which will flash SOS in Morse code. Using your mobile phone you can sent whole messages to the torch to flash out in Morse code. Thanks to my work colleague for suggesting this idea. Other extensions are only limited by your imagination.

Choosing a Java enabled Phone

To use the bluetooth terminal application, Btterm, first you need a Mobile Phone that supports the Java JSR-82 Java Bluetooth API. My old phone did not so I purchased an inexpensive Samsung C3110. I used the website http://www.club-java.com/TastePhone/J2ME/MIDP_Benchmark.jsp to check if the phone would support Java JSR-82.

Checking your existing Phone

If you already have a phone, you can downloaded a test program, bttest.zip, from http://www.microcontroller-bg.com/btterm (after you register).

Loading Java Programs to your Phone

Unzipping bttest.zip gives you two files, BTTEST.jad and BTTEST.jar. You need to transfer these two files to your phone. Depending on the phone, there are three ways to do this:- a) USB cable transfer from your PC, b) copy to a Micro SD card (or similar) and plug the memory into your phone, c) Bluetooth file transfer from your PC.

I used Bluetooth file transfer. Turn the phone on and open "My Bluetooth Places" from the "All Programs" list (under my WindowsXP system). The computer automatically found the phone and listed it. If not you can click "Search for devices in range"



Double clicking on the C3110 icon opens the available connections supported by this phone and the PC's bluetooth stack.



Double clicking on the FileTransfer icon pops up a security dialog in the lower right hand corner of the screen.



Clicking anywhere in the popup brings up the Security Code Request dialog


Enter any security code you like, I used 1234, and click OK

A dialog then pops up on the mobile phone asking for the connection security code. Enter the same code and press OK.


Then a dialog pops up asking if you want to Exchange Data with the PC. Clicking yes sends a folder list to the PC.


Then drag and drop (or copy and past) the BTTEST.jad and BTTEST.jar files into the "Other files" folder, or some suitable folder on your phone. Again the C3110 prompted me to allow Exchange of Data.




Running the BTTEST Java Programs on your Phone

Now that the files are in your phone you need to Install and run the BTTEST.jad file to see if Java JSR-82 Java Bluetooth API is supported by your phone. If your phone does not even have Java support then you will not be able to run the file at all. To Install and run the BTTEST.jad file, navigate to the folder you saved the files to and select the .jad file (not the .jar file) and your options button should give you the option of installing this program. After which you will be prompted to start it. (Note: If Installation is not one of your options, check you have the .jad file selected.)

My phone automatically prompted me to install the BTTEST application and start it. The application ran and reported detecting Bluetooth API V1.1. Which is the answer you are looking for.

If in doubt send the results displayed to http://www.microcontroller-bg.com/contact-us and ask their advice.

Connecting your Mobile Phone to the Bluetooth Controlled Led Driver

Finding the MAC address of your Bluetooth Module

Having confirmed that your phone supports Java JSR-82 Java Bluetooth API, you can order the BTTERM program from http://www.microcontroller-bg.com/btterm . Each purchase is coded to a given Bluetooth module, so after purchasing you need to supply the MAC address of the bluetooth module you want you phone to connect to.

To find the MAC address of your bluetooth module, connect (pair) your bluetooth module to the computer and then right click on its icon and select "Properties" to display the MAC address, or just move the the mouse over the icon. In my case the MAC address for my SparkFun BlueSMiRF_Gold module was 00:06:66:01:e6:a0




Once you have the MAC address of your bluetooth module you can send it to http://www.microcontroller-bg.com and you will receive your copy of Btterm matched to that bluetooth module.

Unzip the Btterm.zip file and transfer both the Btterm.zip and Btterm.jad to your mobile phone, using one of the methods described above. Having transferred the files you need to install and start the terminal program on you phone. The Samsung C3110 prompted me install and start the Btterm program once it had been transferred.

Starting Btterm.

To start it again later you will need to find the .jad file in your phone and click on it and choose the Install or Start option.

When Btterm started on the Samsung C3110, the phone first prompted me to install it (again).




and then to start it.




Then the phone prompted me to allow the bluetooth connection.




Finally the phone displays the stream of ADC readings sent by the Led Controller.




Sending Commands to the Led Driver

The Btterm program lets you type commands directly into the terminal and then send them using the Send button, but because the Led Driver send another ADC reading every seconds the commands you type in scoll off the display. There are two other ways to send commands. The menu button brings up this menu




The Text Input option opens a text input screen where you can type the control character you want to send to the led controller, 0, 1, 2, 3, u or d. and then press the Done button to finish editing and then press the OK button send it.

My Btterm program also came with a quick access menu. Pressing the * key opened a menu of Predefined messages and allowed me to select one of the pre-configured commands to send.




If you want a different set of pre-configured commands, talk to http://www.microcontroller-bg.com about changing the contents of this quick access menu.

Exiting the Terminal Program

As well as using the Exit option from the Menu, pressing the hangup button on the phone prompted me to exit the Btterm program and break the bluetooth connection

Conclusion

This part of the tutorial has shown you how to control your Led Driver from a mobile phone. However the user interface is less then ideal. The third part of this tutorial will cover re-programming the Led Driver to send back user friendly messages and help if the user enters an invalid command. The second part of this tutorial will look at replacing the Bluetooth module with a less expensive one.

Very clever and your excellent write up makes it pretty simple to do.


Thank you for taking the time to write this up and share it, I'm excited to setup some phone controlled lighting in my home. Very slick!

Best Wishes,
-Luke

Very clever indeed !

Mobile Phone Controlled Led Driver - OBSOLETE
See Andriod Controlled Led Driver instead

Note: The Btterm J2ME application used here does not appear to be available any more.
This page is for historical interest only and as an introduction to Andriod Controlled Led Driver using pfodApp which provides many more features then Btterm.

Part 3 - More User Friendly Interface
Enhancing the code to provide a more user friendly interface


As you have seen in Part 1 of this Tutorial, the user interface for remote control of the Led driver is not particularly user friendly, having been designed for development debugging. This part of the tutorial will cover providing more user friendly feedback to the user and simple instructions if they enter an invalid command.

The RemoteLedDriver code still accepts the same user commands u, d, 0, 1, 2, 3, but as you can see in the above screen shot of the mobile phone, if you enter say '1' the driver responds current level and % light (current).

1
>
> Level 4
> Light 2.6%
While if you enter an invalid command, such as 'j', then the drive responds with a prompt of the valid commands, in addition to the current level and level.

j
>
> Level 4
> Light 2.6%
>
> >use keys
> u d 0 1 2 3
Unlike the previous bluetooth drive there is no continuous streaming of the ADC reading level. Although you can use the undocumentd 'i' command to request it. To see what the current setting is just enter any invalid command character.

If you just want to use the driver then downloaded the RemoteLedDriver.asm and set up a new Atmel Studio4 project (as described in "Writing the Program to the uC" on Build a Basic uC Led Driver). You will need to change the .hex file to point to the compiled RemoteLedDriver.hex file. Note: there is no EEPROM file for the RemoteLedDrive, so leave that part of the dialog blank as shown in "Writing the Program to the uC". The previous BluetoothDriver.asm had an EEPROM section, see below for how this data was moved to the code file (.hex)

Note on NewLine format

Different computer operating systems have different ideas of what a new line is. The choices are a single LineFeed char 10 or single CarrageReturn char 13 or the pair CarrageReturn followed by a LineFeed char (13, 10). Most terminal software will allow you to configure which chars are interpreted as newlines. Alternatively the RemoteLedDriver.asm code has a macro NEW_LINE which it uses to send the appropriate new line chars. The BTTERM mobile phone terminal software used here expects new lines to be sent as char 13 and cannot be configure so the NEW_LINE macro is set to send char 13. If you are using the code with some other terminal program you may need to either configure that terminal software to expect CarrageReturn, char 13 as the new line or change the NEW_LINE macro to suit the terminal program.

If you want more information on how the code works then read on.

RemoteLedDriver Code Features

The complete code for this version of the Led Driver is in RemoteLedDriver.asm (see "Writing the Program to the uC" on Build a Basic uC Led Driver for how to set up an Atmel Studio4 project to compile and load this code). This code provides a number of extra features:-
a) If the user sends an invalid command, the driver returns a short message containing a list of valid command chars.

b) When the level is changed, the driver returns the level number and % of max power for that level.

c) When going up and down, logarithmic steps are used to more closely match the human eye's perceived change in brightness.

d) Every 10secs the Led driver send an IamAlive message.

User Help Message

When the user sends an invalid command character to the driver, it would be helpful to let them know which commands are valid ones. When an invalid command is received by the driver, it sends back a two line message

> >use keys
> u d 0 1 2 3
In the previous BluetoothDriver.asm code, the message constants where stored in EEPROM. An alternative is to store the constants in program space. The advantage of storing the constants in the program space is that they can be loaded more quickly and easily. The disadvantages are that they use up program space and the values cannot be changed by the code. Neither of these disadvantages are problems in this case.

To define the message in the program space you use

// .db line must have an even number of chars
// first value is the number of chars to load
Error_Msg_Line1:
// 0 1 2 3 4 5 6 7 8 9 10 11
// > u s e k e y s
.db 11, 32, 62, 117, 115, 101, 32, 107, 101, 121, 115, 32
Error_Msg_Line2:
// 0 1 2 3 4 5 6 7 8 9 10 11 12 13
// u d 0 1 2 3
.db 13, 32, 117, 32, 100, 32, 48, 32, 49, 32, 50, 32, 51, 32
.db defines must have an even number of bytes each. In this code the first byte is used to specify the number of bytes in the message so it can be easily loaded by the program.

LOAD_CHARS_FROM Macro

Here is a routine that loads Error_Msg_Line1 into the RS232 send buffer. It assumes XH,XL register pair has been initialized to the address of the RS232 buffer before this routine is called. e.g.

ldi XH, high(RS232_BUFFER_1+1) // add 1 due to -X in ST -X,Temp below
ldi XL, low(RS232_BUFFER_1+1) // add 1 due to -X in ST -X,Temp below
The routine first sets the Z register pair to the address of the message (note the 2* to convert the address in words to bytes). The lpm instruction then loads one byte at a time into the Temp register and then stores it in the RS232 buffer using the st instruction. The first byte loaded is special, it holds the number of bytes in the message and is not stored in the RS232 buffer but used to set the loop counter Temp2. Note that the Z register pair is incremented after each load and the X register pair is decremented BEFORE each store.

//-----------------------------------------------------
// LOAD_CHARS
// loads chars
// On entry XH,XL is assumed to point to the RS232 Buffer
//-----------------------------------------------------
.def CharCount = r15 // temp reg
.def Temp = r16// Temporary register
LOAD_CHARS:
push CharCount
push Temp
push ZH
push ZL

ldi ZH, high(2*Error_Msg_Line1)
ldi ZL, low(2*Error_Msg_Line1) // Set pointer to RAM data
lpm Temp2, Z+ // this is the number of chars to load
Loop:
lpm Temp, Z+
st -X, Temp
dec Temp2
brne LOOP

END_LOAD_CHARS:
pop ZL
pop ZH
pop Temp
pop CharCount
ret
//------------------------------------------------------
This routine of fine for loading the bytes of one message into the RS232 buffer, but there are a number of messages that the program needs to load. One approach would be to push the current contents of the Z register before call setting it to the message address and then calling the routine to load the message, and then on return popping the the Z register to restore its previous contents. An alternative approach which avoids these extra push and pops for each call is to make the routine into a macro where the Message label is passed as an argument. Macros have been discussed earlier in the RS232 code, you can pass arguments to the macro and access them in the code using the @ syntax. For example if the macro is called LOAD_CHARS_FROM then the following 'statement' (actually a preprocessor instruction)

LOAD_CHARS_FROM Error_Msg_Line1

sets @0 to the text string Error_Msg_Line1

so

ldi ZH, high(2*Error_Msg_Line1)
ldi ZL, low(2*Error_Msg_Line1) // Set pointer to RAM data
becomes, in the macro code

ldi ZH, high(2* @0)
ldi ZL, low(2* @0) // Set pointer to RAM data
and the pre-compiler replaces the @0 with the text passed as the first argument to the macro before it compiles the code.

Compiler Generated Macro

This part of converting the routine to a macro straightforward. The problem comes with converting the Loop: label. You cannot just leave this label as is because the second time you use the macro the label will be defined again and the compiler will (rightly) complain. A simple way round this problem is to let the compiler work out for you the jump count and then hard code this into the macro. To do this, in RemoteLedDriver.asm, uncomment the routine LOAD_CHARS and then compile the file.

Then from the Debug menu, click on "Select Platform and Device.." and select AVR Simulator as the "Debug Platform".


Then choose Debug → Start Debugging. Once the debugger has started you can select the View menu and then open the Disassembler window. This shows the original source code together with the the compiled assembly instructions. Scroll down until you get to the LOAD_CHAR routine and copy and past the entire routine into to top of the source file.


Then stop the debugger. In the source file, comment out all the source lines and remove the code offset numbers and instruction codes at the beginning of each compiled assembly line to leave just the assembly instructions. Finally add the .macro name (LOAD_CHARS_FROM) and .endmacro lines and replace Error_Msg_Line1 with @0 to get the completed macro

.macro LOAD_CHARS_FROM // one argument
//1849: push CharCount
PUSH R15 // Push register on stack
//1850: push Temp
PUSH R16 // Push register on stack
//1851: push ZH
PUSH R31 // Push register on stack
//1852: push ZL
PUSH R30 // Push register on stack
//1854: ldi ZH, high(2*Error_Msg_Line1)
LDI R31,high(2*(@0)) // Load immediate
//1855: ldi ZL, low(2*Error_Msg_Line1) // Set pointer to RAM data
LDI R30,low(2*(@0)) // Load immediate
//1856: lpm Temp2, Z+ // this is the number of chars to load
LPM R15,Z+ // Load program memory and postincrement
//@000002F7: Loop
//: lpm Temp, Z+
LPM R16,Z+ // Load program memory and postincrement
//1859: st -X, Temp
ST -X,R16 // Store indirect and predecrement
//1860: dec Temp2
DEC R15 // Decrement
//1861: brne LOOP
BRNE PC-0x03 // Branch if not equal
//@000002FB: END_LOAD_CHARS
//1864: pop ZL
POP R30 // Pop register from stack
//1865: pop ZH
POP R31 // Pop register from stack
//1866: pop Temp
POP R16 // Pop register from stack
//1867: pop CharCount
POP R15 // Pop register from stack
.endmacro
Note that the brne LOOP statement has been replaced by BRNE PC-0x03 by the compiler. There are no longer any labels in the macro so it can be used multiple times. e.g.

ldi XH, high(RS232_BUFFER_1+1) // add 1 due to -X in ST -X,Temp below
ldi XL, low(RS232_BUFFER_1+1) // add 1 due to -X in ST -X,Temp below

NEW_LINE
LOAD_CHARS_FROM Error_Msg_Line1
NEW_LINE
LOAD_CHARS_FROM Error_Msg_Line2
NEW_LINE
Here NEW_LINE is another macro that puts the new line chars into the RS232 buffer.

The final step in loading the RS232 send buffer with the message to be sent is to set the RS232_SEND_COUNT by subtracting the current XL from this initial value.

//set number of chars
ldi Temp, low(RS232_BUFFER_1+1)
sub Temp, XL
// only need to do the low byte as buffer size < 255
// and sub result above will wrap round to the correct difference
sts RS232_SEND_COUNT, Temp // set number of chars to send
The LOAD_CHARS_FROM macro is used repeatedly in the code to put messages into the RS232 send buffer.

Level and Percent Light Display

In order to send back the current level and % of max power for that level, the code needs to be able to convert from binary to Ascii chars to send to the mobile phone display. CONVERT_13BITS provides this functionality.

A Binary to ASCII formatter (CONVERT_13BITS)

CONVERT_13BITS converts up to 13 binary bits into an ascii string to send via RS232. 13 binary bits is enough to hold any ADC reading or set point. This routine is not the fastest or the smallest, but it is simple to understand and flexible to modify to return different formats. An outline follows here.

CONVERT_13BITS uses a simple subtraction method to do the conversion. It first tests if the number is negative and if so outputs a '-' char and negates the number to make the number positive. The routine then subtracts 1000's, 100's, 10's and 1's in four loops to find the number in each position. For example for the 1000's loop, Temp hold the number of 1000's in the number. Subtract 1000 and if the result is not negative increment temp and loop. If the result is negative then add 1000 back, store the count as an ascii character and go on to the 100's loop

clr Temp
CONVERT_13BITS_LOOP_1000:
subi ZL, low(1000)
sbci ZH, high(1000)
brmi CONVERT_13BITS_ADD_BACK_1000
inc Temp // else inc temp
rjmp CONVERT_13BITS_LOOP_1000 // try again
CONVERT_13BITS_ADD_BACK_1000:
subi ZL, low(-1000)
sbci ZH, high(-1000)
CONVERT_13BITS_STORE_1000:
rcall CONVERT_13BITS_STORE_DIGIT
The ascii char is given by subi temp, -48 i.e temp - (-48) == temp + 48, where temp holds the count.

There formats are catered for by defines

// #define CONVERT_13BITS_LEFT
// left justifies the result eg |-21 and |2
// #define CONVERT_13BITS_RIGHT
// right justifies the result eg | -21 and | 2
// #define CONVERT_13BITS_ZEROS
// right justifies with leading zeros eg |-0021 and | 0002
// if you uncomment more then one you will get a compile error (duplicate label)

These defines control which block of code is used in the routine CONVERT_13BITS_STORE_DIGIT, see the source code for the details. The RemoteLedDriver uses the #define CONVERT_13BITS_LEFT to give left justified numbers with no padding.

Finally for sending the Light Level reading as a % of maximum as slightly modified CONVERT_13BITS_PERCENT routine is used to format 1000 as 100.0%, see the code for details.

Logarithmic Levels

There are 11 predefined levels in the code, 0 to 10. These are provide an approximately logarithmic increase in light level which more closely matches the response of the human eye so each change is level produces a noticeable change in light level. In the previous BluetoothDriver.asm code, the u and d commands just changed the setpoint by 10 each time, but because of the response of the human eye, the step from 20 to 10 was much more noticeable then the step from 100 to 90. The step from 20 to 10 halved the light, while the step from 90 to 100 only decreased the light by 10%. This meant that the top 3 or 4 levels produced little visible change in light. To fix this the levels where changed to approximately logarithmic intervals. No attempt has been made to make the setpoints for each level exact. They depend on the exact response of the human eye and the light output of the LED at various currents. Feel free to vary them to suit you own perception of what are 'even' steps.

The levels are defined by a .dw statement as 11 words (2 bytes == 16 bits). The 0, 1, 2 3 commands are mapped to levels 0, 4,7 and 10, while the u and d commands move up or down one level at a time.

Log_SetPoint:
// 0 == 0, 1==4 2==7 3 == 10
// Levels
// 0 1 2 3 4 5 6 7 8 9 10
.dw 0, 2, 6, 12,26,57,129, 273, 509, 794, 1000 // words
These 2 bytes values are used to set the setpoint for the led current controller for the corresponding level. They are loaded into the SP_Low and SP_High registers by the LOAD_SETPOINT_FROM_LEVEL routine.

LOAD_SETPOINT_FROM_LEVEL

This routine assumes the Temp register contains the level number, 0 to 10 and then uses it to index into the data array of levels.

LOAD_SETPOINT_FROM_LEVEL:
// limit level to Level_Max
push Temp
tst Level
brpl LOAD_SETPOINT_FROM_LEVEL_TEST_MAX
clr Level // set to zero if negative

LOAD_SETPOINT_FROM_LEVEL_TEST_MAX:
ldi Temp, Level_Max
cp Level, Temp
brmi LOAD_SETPOINT_FROM_LEVEL_LOAD // Level < Level_Max
mov Level, Temp //set to Level_Max if too largeLOAD_SETPOINT_FROM_LEVEL_LOAD:
push ZH
push ZL
ldi ZH, high(2*Log_SetPoint)
ldi ZL, low(2*Log_SetPoint)
// add level offset
mov Temp, Level
lsl Temp // 2 times
add ZL, Temp // add Level to addres to get word to load
sbci ZH, 0 // sub 0 with carry

lpm Temp, Z+
mov SP_Low, Temp
lpm Temp, Z+
mov SP_High, Temp
pop Temp
pop ZL
pop ZH
END_LOAD_SETPOINT_FROM_LEVEL:
ret
Note in the code above that because each level is 2 bytes we need to double Temp before adding it to the Z registers to get the correct byte address to load from. The lsl (logical shift left) statement is used to double the Temp register. After the doubled Temp to the low byte of the Z register pair, any carry (overflow) generated is added to the high Z byte using the sbci statement. Subtracting 0 means only the carry is applied to ZH.

Finally the lpm statement is used to load first the Low byte of the setpoint and then the high byte of the setpoint. The .dw statement stores the low byte of the 2 byte word at the lower address. The Z+ form of the lpm statement automatically increments ZH,ZL by one after each load.

I Am Alive Message

The final feature of the code I will mention is the IamAlive message. The idea behind this is that every so often, say about every 8sec, the Led Controller will broadcast it current level and light output if it has not received a command in that time. This means that every 8secs or so your mobile phone will display the current level and light output to tell you the controller is still running and available. It also means that within 8secs after you start your mobile phone BTTERM you should get a message from the driver with the current level and light output which is useful if you just want to check on the status.

The code has a timer and flag for this function. The flag is TRIGGER_IamAlive. This is set by a counter 8sec after the last RS232 transmit. The code routine that uses this flag to send the level and % light is not in the source code provided here and its implementation is left as an exercise for the reader. Things you should consider in implementing this feature what will happen if the user send a command key at the same time the timer goes off. What mixture of messages are sent back to the user? Would they be confusing? Does it matter?