BV4618 User Guide Introduction
Contents
1. The device will also interface to a 4x4 keypad thus it can be used as a complete user interface LCD Interface CHOR Bi Be Be ee L E ee ee z 3 5 E o a 3 e 3 JOMOVOQON 12C Keypad Interface Interface Physical Interfacing This device has no less than three interface options 1 Serial via Microcontroller or conversion device e g USB to Serial or UART 2 Serial via RS232 Old PC Com Port e g 12V 3 12 Only one interface at a time can be used and this is detected on reset The default is serial via microcontroller When pin 4 is connected this is detected as serial via RS232 and when the I2C is connected this is detected as I2C The detection process is automatic Serial Via Microcontroller UART This option uses pins 1 2 3 and 5 of the serial interface This interface it to the left hand side of the controller and pin 1 is marked on the PCB GND Y BV4613 When connecting to a Microcontroller the TX pin on the microcontroller UART goes to the RX pin on the BV4618 and the RX pin on the microcontroller goes to the TX pin on the BV4618 The voltage can range between 3V and 5V however if 3 3V logic is being used then make sure that the LCD display will work on this low voltage At the time of writing 3 3V LCD displays are rare and expensive compared to the 5V types Serial Via RS232 The BV4618 can accept plus and minus 12V on pin 4 of the interface it will also inv2. When pressing the 0 key the scan code codes ar set using Line 8 sets the display to a 4 line by 20 character If this is omitted the display Line 17 gets the state of the interrupt pin Low means there are keys in the keypad buffer that can be read out A simple translation to text is performed and printed out to the LCD display Notes amp FAQ Reset Interface Detection The following table will illustrate how the detection works Priority Mode Pin 4 on Serial Pin 3 on I2C Connector Connector 1 12 n a High by external pull up resistor 1 2 Serial RS232 low 2 low disconnected Serial NOT RS232 high disconnected low disconnected 1 a valid I2C bus will cause the device to use the I2C mode 2 connected to RS232 this is detec ted The TX pin mark or idle should be at a negativ or zero voltage How to stop the display scrolling on last character A feature the end o to the display as the displ of this cont f the line it can be a problem if a be taken 1 Set th on a 20 characte e column leng r disp roller is full scree that when will go to the next lay will also sc n of text h to be slightly la lay set it to be gt 20 the cu line rolla is rger t The requi rsor reaches the last charac nd the top red The following approac hen the actual d
3. BV4618 User Guide Change Version 1 1 I2C updated to remove timing issues Added support for Arduino BV F616 User Guidelines dd aa io Taai aatinaa da a aaa aral dicas 1 Introducti id A de e AAA A RAS de baw A ee ee ees 1 Physical WMS ACTA il ai a A da a a E AS Bid ewes se 2 Serial Via Microcontroller UART ee a a aa e 2 Serial Via RSZ2IZ int A A a Hel Seal oi a 2 WAC di AA A AA A A ARA AAA AAA ale eee eee 3 Keypad LANCER LACS mir A a aa a a aR 3 PN TS iia AAA ARA AAA A ARA AA A ae ee ON 3 Manual Use Geral ua a dada ias 3 Display SLUZO ie a a e oe apd AS a A ces ev By aE a aia wee 5 Pseudo Code sesse AA A AAA E AAA AA 6 Arduino Serial Lai ary emee e Goes A A e lica ae aa 7 BO A o a DRA a dla irte lia laci n aorta atadas Ade 9 Arduino I2 LUDLALY iia a A A A a ee 10 ELO a A A A dal a a a a e a eas ira ara Da 10 EXAMPLE ia a a a a a e ie etal AA id ds a aaa el Oe 11 Notes amp FAQ sd edo esti ay sore Sage A EA AAA A e ae arse we 12 Reset Interface Detection Victim pi a a 12 How to stop the display scrolling on last charactel oooooooooooooooomomooooo 3 Further resources at www byvac com Introduction The BV4618 is a LCD character display controller and will interface with any display that uses the HD44780 or similar device Typical displays are 16x2 20x4 etc The controller enables the display to be used with a serial or I2C interface without taking up and resource from the host
4. If ACK is not There is not need the scan code It may keytops In this case that represent the pressed then put Oxdd 1 The interrupt pin om the key buffer and looks it up in the constant character array If the value can t be found then it will return The keybuffer can be to set this if using keyscan as tha be more convenient to map the keys supply this with a constant array O keytops For e as the first byte in the constant a char keyint Returns 0 if there is a key in the used must be set in the constructor char keyscan This returns the scan code from the char keys Gets the number of keys in the key buffer char key Gets 1 byte fr provided to return a key value Oxff clskeybuf Clears the key buffer This is included but can be also set using puts keydebounce char db This is an arb de int cmd string lay when ent This is the workhorse for getting information out of the display lay and ACK as set in the begin the device ID using this method de itrary value ering values default 50 keypad input A noisy keypad will requir that will be applied as a delay to the a greater value but it will cause a This is included but can be also set using puts It uses the method S th xampl of how to obtain 12C The I2C interface uses a different part of the firmware and works differently from the serial firmware The basic st
5. This text Press CR is designed to fit into 16 characters and so if using a smaller display some of the text will be missing The CR means carriage return or the enter key on the keyboard Pressing lt enter gt will clear the display and produce a on the terminal This is how the Baud rate is determined and should always be the first byte sent The device does not echo any character and so to see what you are typing switch this on via the settings menu About Text transfer Font Background Refresh Ports Show Control Chrs H Zed Kurt Basic vodafone bas Any thing you type from now on will go to the display To see the device ID type esc 31d The esc means the escape key on the keyboard this is usually top right and is one keypress so the above command is a total of 6 key presses which will send 6 bytes to the device 0x1lb 0x5b 0x3f 0x33 0x31 0x64 The command is carried out as soon as the last character d in this case is received This is how all commands work in serial mode It should be obvious from the above that the character Case is important for example esc 31D is a different command from esc 31d With the above setup it is possible to try out all of the commands and understand how they work before implementing in software This is also a good debugging tool as you can type the commands that the software would do and see if there are any errors Display Size The default display s
6. for all of this and advantage is taken of the built in compiler escape codes To write to the display use puts lt string gt from BSerial Some Examples assuming bv is the instance of the class MNe 23 clear the screen bv puts e 4hL e 20c set display to 4 lines by 20 bv puts e 261 turn off the back light e 3 5HFred print Fred on the third line 5 column bv puts vb puts Basically look at the command table in the datasheet and substitute esc for le and that it Input or Read This is always more difficult and to help some methods have been created to get information from the device The best way to see this is to have a look at the example Setup 5 Examp he as BOS nd o sing oe There are a few options for setting up wo or three options t BV4618 S bv rxPin txPin int pin The first two parameters are obvious The last one is a pin to specify for the interrupt pin on the device the value on the pin When the class has been instantiated begin lt Baud rate gt lt delay gt lt ack gt le begin 9600 0 receiving data from a serial port character For how the device This can then be used by Specifying the pi n value is opt will work the keyint ional T xampl are two methods an ACK character of retrieving the number of used in this device characters are f
7. limits the usefulness of this command when using I2C cls Clears the screen and sets the cursor in the home position clright Clears a line from the current cursor position to the end of the line cleft Clears a line from the current cursor position to the beginning of the line clall Clears the whole line that the cursor is presently on setkeycodes const char codes The keybuffer can be interrogated with keyscan or keys There is not need to set this if using keyscan as that will always return the scan code It may be more convenient to map the keys to the values on the keytops In this case supply this with a constant array of the scan key codes that represent the keytops For example if the scan code is Oxdd when 0 is pressed then put Oxdd as the first byte in the constant array char keyint Returns 0 if there is a key in the key buffer otherwise 1 The interrupt pin used must be set in the constructor char keyscan This returns the scan code from the key buffer char keys Gets the number of keys in the key buffer char key Gets 1 byte from the key buffer and looks it up in the constant character array provided to return a key value If the value can t be found then it will return Oxff clskeybuf Clears the key buffer keydebounce char db This is an arbitrary value default 50 that will be applied as a delay to the keypad input A noisy keypad will r
8. equire a greater value but it will cause a delay when entering values Example Wiring the display is straightforward Connect the BV4618 to the Arduino using the 5V and GND lines SDA goes to A4 and SCL goes to A5 on the Arduino Pin 9 D9 was used as the interrupt pin and this goes to the Int pin on the BV4618 A 4x4 keybaord was also connected to the BV4618 1 BV4618_ I dif Ox31 9 4 x 20 display 2 3 void loop 44 5 const char kb 0x7d Oxee Oxed Oxeb Oxde Oxdd Oxdb Oxbe Oxbd Oxbb 6 char tmp 7 f f set up display geometry 8 di setdisplay 4 20 3 f set up keyboard scan codes alter the above constant array 10 f f this will depend on how the keypad has been wired 11 di setkeycodes kb 12 ZZ aleae screen 13 di cls j 14 di puts Display Test 15 di rowcol 2 1 16 while 1 17 if di keyint is tmp di key 19 if tmp gt 9 tmp 4 10 20 else tmpt 0 21 di putch tmp 22 di putchi Ja 23 24 25 while 1 26 The above is an extract from th xample Lin I2c address 7 bit and the pin that is used for the interrupt 1 initialises the class and passes the Line 5 is the constant character array that is used to translate scan codes to key numbers there is a few values missing from this picture 0x7d was returned when pressing 1 Oxee was returned etc Th di setkeycodes controller will default to 2x16
9. ert that signal so as to be compatible with the microcontroller interface Th device does NOT put out plus and minus 12V but most RS232 interfaces will tolerate this Again the output is inverted because the RS232 describes an inverted signal BV4613 RS232 pin3 TX gt gt BV4618 Pin 4 RTS NOTE that pin 4 is marked RTS in this mode it is actually RX that can accept plus and minus 12V When using this interface power will need to be supplied to pin 3 This must not exceed 5V and preferably be regulated The RS232 COM port interface cannot provide this power 12C The I2C interface is at the bottom of the controller and can be connected to any I2C bus The bus must of course have pull up resistors these are not provided on the BV4618 The default 8 bit address is 0x62 write and ox63 read The 7 bit address is 0x31 7 BV4613 NOTE on version e of the PCB the SDA an V lines have been marked up wrongly they are covered with a sticker The above diagram shows the correct wiring Keypad Interface The keypad interface has 5 outputs C0 C3 amp nInt and 4 inputs RO R3 The Column outputs C0 C3 are constantly being changed this is detected by the software when a key is pressed and the signal goes to one of the inputs After a suitable denounce period the key is registered and the scan code placed in a buffer When there is a value in the key buffer the nInt line will go low and remain
10. isplay cursor will still jump at t The I2C bus specification requires pull up resistors and so simply connecting to thus when ter at This may be a problem at the bottom line will disappear This hes can for example he end of the line to another line but this may not cause it to scroll esc x yH can be used for positioning Experiment with the number of characters that is best for your purposes 2 Use LCD direct commands to position the cursor The internal variables will not be updated and so the commands should be used all of the time The command is esc lt num gt E where lt num gt is a potion on the display Column 1 Column 20 Line 1 128 147 Line 2 192 211 Line 3 148 167 Line 4 212 231 Using this command will position the cursor in any position on the display for example on a 20x4 line display to place x on the last column on the last line use esc 231Ex The cursor will jump to the start of the display when will no 3 scrolli Version 1 2 ng scroll after 20 1 11 hS r x is entered but the display added a no scrolling command esc 1x to turn off
11. ize is 16x2 that is 2 lines by 16 characters For this device the size of the display is important as it will determine when the text has reached the end of the line and when scrolling needs to begin The first operation the software should carry out after determining the Baud rate is to set the display size to whatever is connected to the device For example if a 20x4 display is connected the following commands are needed esc 4L sets number of lines to 4 esc 20c sets number of characters or columns The device will revert back to its 16x2 default on reset so these commands must form part of the initialisation sequence The commands should really be entered thus esc 4Lesc 20c This will set the display to 4 lines 20 columns as a continuous stream because everything including CR and LF other than a command will be sent to the display so having a CR between the two commands will cause the display to perform that action i e go to the beginning of the line and down one Pseudo Code Using the display as part of a system requires sending and receiving serial data accurately It is easy to miss a character or put an extra one in like CR and this will throw the whole function out To demonstrate a typical application pseudo code will be used it can then be translated to any particular language There are only a few simple functions needed com _putc character outputs a character to the com por
12. low until all of the keys have been read out The data sheet has full details on how this works Software The device is intended to be used with automated systems and software as it can provide a complete user interface It is however advisable to understand how the device behaves by manually inputting commands This will save time later and also help with better software functions later on The first part of this section is therefore using the device manually from a terminal Manual Use Serial For this we will use BV COMM the best place to download this is form here http www asi byvac com da data php it is free and does not need any installing simply run the exe You can connect via RS232 or via a USB to serial interface BV103 BV104 http www byvac com bv3 index php route product products path 488 product id 84 Start the terminal select a suitable COM port and don t forget to press the connect a icon to turn it green NOTE This device autodetects the Baud rate on pressing enter the image below shows the Baud rate at 115200 stop bite 2 and data bits 8 BV Com ajja ame i JE y H ZediKurt Basic vodafone bas If connecting Via a BV101 then the display will say Press CR if connecting via RS232 then the display will say 232 Press CR This is automatically detected at reset and the display will operate in that particular mode until reset again
13. lumn position lineposition char line char pos To move to the start of a particular line on a display an address is sent as a command This address is normally 0x80 0xc0 0x94 and 0xd0 for lines 1 to 4 respectively However on a 2 line x 40 display or some other combination this may not be the case This command will set the starting line address for the line specifed backlight char blon Turns the back light on and off 1 is on crhome Returns the cursor to the home position without clearing the screen int deviceid Obtains the device ID which will be 4618 this is useful if multiple devices are on the same bus version char ver Gets the firmware version as a string setaddress char newaddress Sets a new 12C address for the device The new address will not take effect until the device has been reset reset Resets the devic resetEEPROM Resets EEPROM back to the factory settings this will also set the I2C address back to its default setting delayms char del Causes a delay of del milliseconds the display will stop responding for that time As there is no ACK mechanism for I2C there is no way to tell if the delay has finished so it limits the usefulness of this command when using I2C delays char del Causes a delay of del seconds the display will stop responding for that time As there is no ACK mechanism for I2C there is no way to tell if the delay has finished so it
14. orthcoming about f every output from the device this is called a 12 would VAS how do you know to wait for the 2 of 12 and 1 100m8 is to s 2 to be 12 So it how do you know that you must be followed by begin The class itself has method and return nav return 12 and not 1 imply wait until nd ACK In th received th keys in the buffer could return you are sure have a special character at the no is a simple xampl natter to wait given and for 55 not 0 it does he advantage of thi environment the ACK be advisable in that W l 5 T more e u t 2 T Using this with the required then set it setkeycodes const char codes he ACK and anything before it not have to be may be situation begin method is the correct output ap s is speed as there is no unnecessary waiting nissed and thi s will spoil set delay to a value in mS used with ACK although I cant see there will be a reason to do so to 0 and it will be ignored interrogated with keyscan t will always return to the values on the f the scan key codes xample if the scan code is Oxdd when 0 is rray key buffer otherwise key buffer ACK can be any value from 1 rintable character or keys CO however in a noisy the output so just a delay may delay can also be
15. rategy is to display any byte received via I2C on the display unless it is a Oxlb in which case a command will be expected To make things cleared the following notation will be used s This is a start condition followed by byte 0x62 which is the 8 bit default write address of the device In some systems this is a 2 function operation thus i2c_start i2c write 0x62 In practice these two operations can always be combined because the device address always follows the start condition P This is the stop condition g n This will receive bytes from the device where n is the number of bytes to receive for example g 3 number Any number on its own will be sent to the I2C bus Hex values r Is a restart command always used after sending a command that will return some values This may be implemented in some systems as i2c_stop i2c_ start i2c send 0x62 1 Note that the 8bit address is now 0x63 because an odd numbered address will indicate to the device that data is being requested To send Hello to the display requires the following s 48 65 6c 6c 6f p To clear the display would be s lb 50 p To receive the device ID s lb 40 r g 2 p When reading from the device take for example the ID bytes a command is first sent to request the bytes and then they are read out by the master There is a very small delay between the request and the device presenting this data on the I2C bus During this time clock st
16. retching is used and if the host implements this then no further consideration is necessary as this will be correctly read by the host If the host does not implement clock stretching then a small delay between the requesting command and receiving command is recommended Initialization of a 20x4 the display would be s 1b 30 4 p set number of lines to 4 s lb 31 20 p set number of characters to 20 Arduino 12C Library Support has been added by way of an Arduino Library 12C Class BV4618 I BV4618 char i2adr char int pin i2adr is the I2C address of the device int pin an input pin that is used for detecting when there are keys in the buffer BV4618 char i2adr Alternative is interrupt pin is not used It is possible to pole the keyboard buffer with keys to see if there is any keys in the buffer and so the interrupt will not be required This does load the I2C bus and processor more though setdisplay char cols char rows Sets type of display or rather the number of lines and characters it has putch char c Sends a single character to the display puts char s Sends a string to the i2c bus The string must be a string i e null terminated crup Moves cursor up one line crdown Moves cursor down one line crright Moves cursor right one space crleft Moves cursor left one spac rowcol char line char col M oves the cursor to a specified row and co
17. t com puts string outputs a string to the com port com getcq returns 1 if there is a character waiting otherwise returns 0 com getc gets a character from the com port function init display put here code needed to initialise the com port com _putc 13 send CR to establish Baud rate wait 500ms needed to establish Baud rate set up display for 20x4 com puts 0x1b com putc 41 4 lines com puts 0x1b com putc 20c 20 chars set ACK to com puts 0x1b com pute 42k7 7 42 is end function In the above part of the initialisation is to use the ACK mechanism this will prove useful when obtaining values from the keypad function send text string com puts string end function function position row col com_putc 0xlb com_puts command is esc r c H r convert_to_string r c convert_to_ string c com puts r cS H end function The above two functions simply use the commands to send text and move the cursor function get_value command val com puts command send command while com_getcq lt gt 0 v com_getc if v break finish when ACK received valS valS v wend return val end function The above is a bit more complex but shows the principle of obtaining information from the device Suppose we need to obtain the device ID which is command esc 31d the func
18. tion may be used thus print get value 0x1b 31d To explain the command will be sent to the device and the device will respond with 4618 The get_value function will collect all of the bytes form the device until it encounters the ACK byte which was set to this during initialization ACK can of course be set to any value between 1 and 255 42 Just happens to be the ASCII code row EP All values returned form the device are in text so these need to be converted to values to use in a program For example suppose the key scan code contains 221 and this is returned using esc k e g af get_value 0x1b k The a will contain 3 bytes as a string 221 This can be a common pitfall by wrongly expecting a single byte value of 221 Arduino Serial Library The Arduino serial now uses BSerail which can be found here http www asi byvac com da data php it is in the ASI link ASI is not needed for this display but BSerial is The methods inherited from BDerail are Methods inherited from BSerial baud rate INEINCIS INES ss Bi WaLiMicls Cs Ie flush puc cnt unsigned char puts char s unsigned char buffer char getch A description of what they do and how they work are in the ASI library zip which is at the link indicated above under ASI Writing to the display including setting up is simply sending text and so a single method is used
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