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Flowcode Graphical Programming Flowcode C v oid interrupt( v oid) { if ( intc on & 4 ) { c lear_ bit( intc on, 2 ) ; F C M _ IN T E R R U P T _ T M R o( ) ; Assembly movlw bsf S T A T U S , R P 0 bc f S T A T U S , R P 1 m ov wf _ adc on1 movlw 1 2 m ov wf _ option_ reg Hex :0 4 0 0 0 0 0 0 8 A 0 1 1 2 2 8 3 7 :0 8 0 0 0 8 0 0 F 0 0 0 F 0 0 S 0 3 0 E F 1 0 0 0 0 :1 0 0 0 1 0 0 0 0 4 0 E F 2 0 0 0 A 0 E F 3 0 0 B A 1 1 0 A 1 2 2 9 2 8 3 5 2 8 6 C :2 0 0 0 2 0 0 D 9 2 8 F E 2 8 0 7 3 Programming with Flowcode – Part 4: Designing a Digital Clock W e are going to start a new project this month. It will build on ideas from previous columns but also introduce two new and very useful components, plus we’ll refresh some earlier programming ideas and incorporate some new ones. First a little housekeeping – as always, all the parts in this project come from the free-to-use component library of Flowcode, so you can build this in Flowcode without making any code purchases. For more details, do see the Flowcode try-before-you-buy box at the end of this article. Project overview It’s no secret that one of the most useful and widely used applications of digital technology is timekeeping. So, for our next Flowcode project we will assemble and program a system to create a simple digital clock. This will help to extend your understanding of Flowcode and illustrate ideas and techniques you can use in your designs. The Flowcode Digital Clock hardware will consist of four main parts: a microcontroller, a display, an RTC module and a keypad. The microcontroller is our usual Arduino Uno clone, the RedBoard. The display will be the same 16x2 LCD we used last month. The two new components are the RTC (real-time clock), an inexpensive module based on a DS1307, DS3231 or DS3232 IC, and a simple, lowcost membrane keypad. Whichever IC the RTC module uses, it keeps time with a precisely repeating pulse (the ‘clock’) plus some initialising set-up data which is stored in non-volatile SRAM. It uses the stored data and clock pulse to accurately calculate the time and date, which are then sent out via its I2C bus. The module generates seconds, minutes, hours, day, date, month and year information. The end of the month date is automatically adjusted for months with fewer than 31 days, including corrections for leap year up to 2100. Plus, it works with the 24-hour or 12-hour format via an AM/PM indicator. 48 Fig.1. Typical inexpensive RCT module based on the DS3231 IC You can also set alarms. So, all in all, it’s quite a handy device for clock builders. As explained, the free Flowcode RTC component can support each of the DS1307, DS3231 or DS3232 ICs, and I used one with the DS3231 – see Fig.1. At the time of writing, you can buy a module based on this IC for under £5, for example eBay item 125318625863, but there are many other vendors. Naturally, you need a way to set up and initialise the RTC with the current time/date, and to do that we will use a membrane keypad. These simple and inexpensive devices are a great way to interface with digital projects, and learning how to use it in this Flowcode project will help you in a host of other designs. I used the 4x4 type shown in Fig.2. There are many sources for these; for example, eBay item 275255946762. This won’t be a PIC project. Unlike more modern PIC devices, the free Flowcode PIC16F88 we have been using does not support the I2C protocol, which rules it out for communication with our RTC of choice. As well as the two new Flowcode components, we will also use some new Flowcode programming techniques, in particular we will learn about: n Byte-to-string conversion n Global and local variables n The difference between == and = n The logical operators && and ||, plus comparison operators > and < n Calling a User Macro and passing input parameters n Returning a value from a User Macro. Naturally, all the Flowcode for this project can be downloaded from the July 2022 Fig.2. 4x4 membrane keypad. page of the PE website, and don’t forget that if you get stuck there are helpful forums at: https://flowcode.co.uk/forums/index.php Fig.3. Project Explorer with the main components added. Practical Electronics | July | 2022 Fig.4 (left) Keypad before editing, and (right) after editing. Digital Clock parts list The parts you will need for the Flowcode clock project are as follow: n Solderless breadboard n DS1307/DS3231/DS3232 Real-time clock (RTC) module n Keypad – 4x4 membrane type (note, only 3x4 buttons used) n 16x2 LCD – LCD 1602 (or 2004) with HD44780 chipset (see PE, April 2022) n Trimmer resistor – 10kΩ contrast adjustment for LCD n 4x 100Ω resistors – pull-downs for RedBoard ports n 3x 10kΩ resistors – in series with keypad, protects RedBoard n Jumper wires. Adding Flowcode components To start, load Flowcode and set the target as the RedBoard (see PE, January 2022). Next, the components are added from the Components ribbon, either via search or by selecting a component category. To add components using search, use the following terms in quotes and then select the item listed on the right: Item Term Keypad ‘key’ LCD ‘lcd’ Real-time clock ‘rtc’ Choice Keypad (Generic) LCD (Generic, 16x2) Real Time Clock (Internal, DS1307, DS3231, DS3232) After all the components have been added to the 2D panel, Project Explorer should look like Fig.3 (with the component functions minimised). Now look at the keypad on the 2D panel – it will look like Fig.4 (left). So why only a 3x4 device when I’ve specified 4x4? The reason is that this Flowcode keypad component was originally designed just for a 3x4 device. However, it has now been updated to cover both 3x4 and 4x4 versions. It also works with both decimal and hex keypad varieties. We have a 4x4 keypad as it offers greater flexibility for future project expansion, but initially we will only use it as a 3x4 device, as explained below. Fig.5. Editing the keypad’s properties If you don’t make this change the keypad will not work as expected with the program. After the change has been implemented, the keypad will look like Fig.4 (right). When it comes to wiring the keypad, its cable connector terminals have the row (R) and column (C) connections from left to right shoen here: R1, R2, R3, R4, C1, C2, C3 and C4. (This is the usual arrangement, but if possible, do check with a datasheet or vendor specification.) Now we need to set one RTC property. Select the properties of the RTC and make sure Simulate Comms is set to No. Programming foundations Next, we are going to lay some foundations for the Flowcode program which we will build next month. This will be a more involved program than the ones we have looked at so far, and we need to expand our repertoire of Flowcode tools to build a useable digital clock. We will expand some of the concepts used in the Traffic Lights (PE, February 2022) and LCD Temperature Monitor (PE, April 2022) projects, plus introduce some brand new ideas. Variable and operators Two of the most important concepts in programming are the ideas of ‘variables’ and ‘operators’. We’ve already met some kinds of variables in our earlier programs, but now would be a good time to clarify some of their properties. Also, we will make use of operators in the clock program, so we will provide an overview of those too. Setting properties Variables Next, we need to set some component properties in our keypad and RTC. We want to change the keypad so that its Flowcode image matches the three left-hand columns of our actual keypad. This means changing the bottom row so that left to right, it will read * 0 # instead of 0 A B. Referring to Fig.5, we do this by changing the properties of the keypad component. Open the properties window and edit the Return Values. In the ASCII box, change: 1234567890ABCDEF to: 123456789*0# (ie, replace 0ABCDEF with *0#) A variable is a value that can change, depending on conditions, a calculation or based on information passed to the program. It can represent the value of something physical – say temperature – or it can be something more conceptual, say an interest rate. Such variables have a numerical value and there is a choice of numerical formats (floating point, integer, byte). Alternatively, a variable can indicate a system’s logical status (eg, True/False, yes/no, on/off, 1/0). Another important category of variable is a particular ordering of characters, typically called a ‘string’, or less formally, ‘text’. In the Numbers box, change: 1,2,3,4,5,6,7,8,9,11,10,12,13,14,15,16 to: 1,2,3,4,5,6,7,8,9,11,0,12 (ie, delete ,13,14,15,16) Global and local variables Practical Electronics | July | 2022 Whatever the variable type or whatever it represents, variables can be classed as either ‘global’ or ‘local’. If it is global, 49 String variables are used for storing and comparing text. (In fact, a short piece of text is called a ‘string’.) When defining them, the string must start and finish with double quotation marks. For example, suppose we want a global string variable called MyString, and we want it to contain the string Hello World, then we would type: MyString = "Hello World" Fig.6. Adding a new global variable in Project Explorer. then the variable is available for use in in any User Macro within the whole program. On the other hand, if it is a local variable then it will only be available within the User Macro in which it was created. Furthermore, once the User Macro has finished (ie, the program has moved on to a different User Macro) the local variable will be erased, and it is not available for other User Macros. If the User Macro is accessed again then the local variable is created afresh, starting with whatever initial value the User Macro assigns. Top programming tip: it is good programming practice to use local variables whenever you can. Global variables use more memory resources and local variables encourage better programming and more reliable programs. You can spot a local variable because it must always start with full stop / period; eg, .MyLocalVariable You add variables from the Project Explorer (as shown in Fig.19 and Fig.20 in the PE, February 2022 Flowcode article). Fig.6 below shows the result of clicking on the ‘Globals’ icon. Next, click on <Add new> under Variables and then enter your variable data in the resulting variable window. Local variables are added in a similar way by clicking on the icon to the right of ‘Globals’in the Project Explorer. Note that when creating a local variable you must be in the User Macro where the local variable is to reside. String variables We mentioned numerical and logical (True/False, on/off, 1/0…) variables above, and since we covered these in previous articles (see: PE, February 2022) we won’t expand on these here. However, although we introduced string variables in the LCD Temperature Monitor (PE, April 2022), we didn’t go into a great deal of detail, so let’s a take a closer look. 50 The default size of a string variable is 20 bytes, which is 20 characters. This can be changed by entering the number of required bytes into Array Length in the Create A New Variable window, you then click Add Array Dimension. The square brackets at the end of the string name will be the number of bytes used. Always bear in mind that the more bytes assigned, the more memory is used within the microcontroller, so it’s best to keep the assigned string length as short as possible. (Again, see Fig.19 and Fig.20 in the PE, February 2022 Flowcode article.) String conversions Things start to get more interesting when you manipulate string variables. You might want to convert a string to a byte variable or a byte to a string variable. For example, suppose you wanted to enter the time ‘09’ to be displayed on the LCD; entering the numeric value ‘09’ as a byte will result in just 9 being stored, so only 9 will be displayed. However, if 09 is a string, then it will be stored and displayed as ‘09’. There are quite a few functions that operate on strings, and they can be found by selecting the f$ icon, top right of the calculation icon. In this project we will use two of these: ToString$() and StringToInt$() ToString$() converts bytes or integers into a string, for example: TempString = TempString + ToString$ (.ReadKeypad) This expression (see below for an explanation of the term ‘expression’) will take the number that is assigned to the local variable .ReadKeypad, convert it to a string and ‘add’ it to whatever is the current value of the string TempString. If TempString is the string 1 and .ReadKeypad is the number 6, then ToString$ converts the number 6 to the string 6 and adds it to the contents of TempString creating the string 16. It’s important to note that this new 16 is a piece of text, it is not a number. Likewise, StringToInt$() converts a string to an integer. Naturally, it can only convert strings written with number characters. So to converts the string 123 to the integer 123, you would use StringToInt$(123) Operators Variables are clearly useful, but you need a variety of ways to manipulate them – just as we did with the simple string ‘addition’ example above. This is where operators come into the picture. An operator is a process which ‘operates’ on a variable or value. For example, you will recognise these basic arithmetic operators: +, –, /, * and =. Operators are applied to ‘operands’ (variables and constants) and these combinations are used to create an ‘expression’, which can reduce multiple variables to a single value. For example, 6 + 4 = 10 is an expression that takes two operands and reduces it to one value. Likewise, you could add together two numeric variables to create a new value: CostofProject = Parts + PCB Also, as we saw above, you can use some operators on strings to create useful expressions, and in this case, the expression’s output would also be a string. Comparison operators In programming, an essential class of operator make comparisons between operands (variables and constants). There are five varieties of these, and they each ask one of five questions about the relative size of the two operands, here generalised to x and y: x > y is x greater than y x < y is x less than y x >= y is x greater than or equal to y x <= y is x less than or equal to y x == y is x equal y These operators are used in decision making branches, and their outputs are the characteristic ‘yes’ or ‘no’ that you see in flowcharts. Use == or = for comparisons? Notice that for the equals comparator above I wrote a double-equals sign. The equals sign (=) has more than one use in Flowcode. For example, a single = is used for all assignment operations, so to set a variable to a value we use: SetTime = 11. You can use the single version in comparisons, but to avoid ambiguity it’s best to use the double version for a comparison operator. Logical operators Flowcode has operators that act like the familiar logic gates ICs, producing logical AND and logical OR: || && Flowcode OR Flowcode AND Practical Electronics | July | 2022 The character ‘|’ is known as the ‘pipe’ symbol. You can find it to the left of the key Z on a standard UK computer keyboard. Note that you must type two pipes or two ampersands (&) to create an OR operator or AND operator – one won’t work. Brackets When you combine several operators and operands in one expression, it can become difficult to work out exactly what the expression is supposed to mean. A simple example from arithmetic is: x = 2 + 3 x 4. There are two possible ways of looking at this. Do you multiply 3 times 4 and then add 2 to create 14; or, do you add 2 to 3 and then multiply by 4 to produce 20? Now, although there are strict rules for interpreting this kind of expression this example does highlight that ambiguity can creep into expressions and it’s easy to make mistakes, which can be a nightmare to troubleshoot. The best approach is to use brackets to effectively create sub-expressions; for example, x = (2 + 3) x 4 or x = 2 + (3 x 4), depending on what you want to calculate. It never hurts to liberally sprinkle brackets in your expressions and thereby make it clear to yourself (and anyone else who might use or edit your code) what you intend the expression to do. You can use brackets with logical operators too – in fact they are especially useful with this type of expression. For example, here is an expression from some code which we will meet later in a User Macro called TimeSetValidity (KeypadValue == 1 && SetTime > 23) || (KeypadValue == 2 && SetTime > 59) || (KeypadValue == 3 && SetTime > 59) This might look a little daunting at fi rst, but the use of brackets makes it much easier to understand; all it is doing is asking if: The KeypadValue is 1 AND the SetTime variable is greater than 23 Fig.7. Setting up the .Return facility of a User Macro value of (for example) the Hours variable to be available, then the last expression within a calculation icon must be: .Return = Hours The local variable is only ‘Returned’ on exit from its User Macro and only one local variable can be returned. Any kind of variable (float, string, byte, integer) or just a number can be returned. User Macros often also need to receive parameters – this is called ‘passing’ parameters and allows a User Macro to be given values from other sources. You can pass as many different parameter as you like. These parameters are set up in the Parameters box of the same User Macro Properties window as the Return item (Fig.8) OR The KeypadValue is 2 AND the SetTime variable is greater than 59 OR The KeypadValue is 3 AND the SetTime variable is greater than 59 The answer to this whole expression will be ‘yes’ or ‘no’, and from there the program will branch one way or another. Try writing out the expression without brackets and you will see that it becomes much harder to understand – do you apply AND or OR first? Remember, when it comes to expressions, brackets are your friends – use them! Call macro parameters and return values I mentioned above that it’s always better to use local variable where possible – but that a local variable is erased when the program exits the User Macro where it is used. This does of course present a problem if the value of the local variable is of potential use in a different User Macro. The way round this conundrum is to ‘Return’ the value. When you create a new User Macro, if you require a value to be delivered to another User Macro then go to the Properties window and enter the local variable in the dropdown of the Return Value box (see Fig.7). Also, the value of the variable will only be passed back if it’s assigned to the .Return local variable. For example, if you want the Practical Electronics | July | 2022 Fig.8. Adding a parameter 51 Program overview 5. If not, it waits for 100ms and then returns to item 3 and repeats. 6. If a key press has been detected then the microcontroller checks if key 1, 2 or 3 was pressed via the next three decision boxes. If not, it returns to item 3. Note: at this point in the flowchart the program is designed to only move on if 1, 2 or 3 is pressed. All other keys will be seen as an error and ignored. 7. If 1, 2 or 3 has been pressed the program passes this information to the Run set time routine. A 1 means Hours are to be set; a 2 means Minutes; and a 3 indicates Seconds. We’ve covered a lot of useful theoretical material. Now, we return to the project and discuss program operation. Fig.9 shows an overview of the Digital Clock’s flowchart. 1. At power up, the program commences with Start. 2. The microcontroller initialises the RTC and LCD. 3. The microcontroller retrieves Hours, Minutes and Seconds data from the LCD and sends it for display on the LCD. 4. The microcontroller checks the keypad value and determines if a key has been pressed. Start Initialise LCD and RTC 8. The Run set time routine waits for the Hours, Minutes or Seconds data, plus a terminating # key press. If a # is not detected, then the program returns to the start of the Run set time routine. 9. If you enter the wrong digit you can exit and re-enter the Run set time toutine by pressing the the * key. 10. When the # key is detected a time validation is performed. This is to check if a nonsense value has been entered, for example 83 Seconds. If a false value has been entered then the digits are cleared and the program returns to the start of the Run set time routine. 11. I f valid time data has been entered then these are written to the RTC and the program returns to item 3. The program continues to loop round from item 3 to 11 until the circuit is powered down. Set RTC time Retrieve time from RTC, send time to LCD Has key 1 been pressed? Read keypad value Has a key been pressed? Run set time routine Y For Hours N Y Has key 2 been pressed? Next month That’s all for this month except to say that the Digital Clock Flowcode program which we will cover in detail next month is available for download from the July 2022 page of the PE website. Do have a look at it now before we dive into all its details in the August issue! N Y For Minutes Has key * been pressed? Y Clear digits N N Delay 100ms Has key 3 been pressed? N Y For Seconds Enter time digits, followed by * or # N Has key # been pressed? N Y Time validation check OK? Fig.9. Flowchart of the Flowcode Digital Clock program. Y Martin Whitlock is an Applications Engineer at Matrix TSL – the company which is behind Flowcode. Try Flowcode for free! We hope you found this article interesting. If you’d like to try Flowcode for free then just go to https://flowcode.co.uk/download/ and download the code. You’ll get a 30-day free trial of the full version – but that’s not all. Even after the 30 days are up your copy of Flowcode will continue to work, but at a reduced level with a limit on the size of program you can run and access to a more basic set of parts. However, for beginners it is still an ideal platform with which 52 you can build and run programs, on for example, the Arduino Uno/ RedBoard or a PIC 16F88 that we are using in this project. Only when you are sure that you want to use Flowcode do you need to buy inexpensive access to say a Raspberry Pi or Bluetooth module. (See: https://flowcode.co.uk/ buy/process/ for all the modules available and what they contain.) What’s more, as soon as you buy any module, the restrictions on the size of your code are removed. If you get stuck with anything relating to Flowcode use (installation, software, creating flowcharts, compiling to hardware, hardware not working…) then there are forums set up to help you: https:// www.flowcode.co.uk/forums PE discount! One more thing – Flowcode is deliberately designed to be inexpensive, but PE readers can get a further 20% discount when they use the code PE20 at checkout. Practical Electronics | July | 2022