{"id":314,"date":"2009-02-22T13:43:54","date_gmt":"2009-02-22T12:43:54","guid":{"rendered":"http:\/\/www.evertdekker.com\/wp\/?p=314"},"modified":"2023-01-03T15:52:40","modified_gmt":"2023-01-03T14:52:40","slug":"max7456-video-overlay","status":"publish","type":"post","link":"https:\/\/evertdekker.com\/wp\/?p=314","title":{"rendered":"Max7456 video overlay"},"content":{"rendered":"
\n

The Max7456 from Maxim is a monochrome video overlay chip. With this you can overlay text and simple graphics over your PAL or NTSC video signal. You can also use it with no overlay, just like a simple monitor.<\/p>\n

<\/div>\n

Included in this sample is a tutorial how you cam make your own characters with my converter tool. This tool converts the Maxim mcm files to Bascom data lines.<\/p>\n

 <\/p>\n

Syntax<\/h4>\n

Videotext<\/span> string, y , x<\/p>\n

Remarks<\/h4>\n\n\n\n\n\n
\u00a0String<\/td>\n\u00a0String to be displayd<\/td>\n<\/tr>\n
\u00a0y<\/td>\n\u00a0Constant or variable with y position.<\/td>\n<\/tr>\n
\u00a0x<\/td>\n\u00a0Constant or variable with x position.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

There are some controle characters implanted to controle (part of) the string.
\nAscii 133=start blinking text, 134= stop blinking text
\nAscii 131=enable the background, 132= disable the background
\nAscii 135=invert text, 136= non-inverted text
\nIn Bascom it’s easy to use this with {133} option, like:
\nVideotext “{133}Flashing text{134}”, 9 , 0<\/p>\n

 <\/p>\n

Syntax<\/h4>\n

Rowbrightness<\/span> row, brightness<\/p>\n

Remarks<\/h4>\n\n\n\n\n
Row<\/td>\n\u00a0Row number to change 1-13 for NTSC , 1-16 for PAL<\/td>\n<\/tr>\n
Brightness<\/td>\n&B0000xx11 Character Black Level in % of OSD white level
\n00 = 0% 01 = 10% 10 = 20% 11 = 30%
\n&B000011xx Character White Level\u00a0 in % of OSD white level
\n00 = 120%\u00a0 01 = 100%\u00a0 10 = 90% 11 = 80%<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

Syntax<\/h4>\n

Writecustomcharacter<\/span> Characters<\/p>\n

Remarks<\/h4>\n\n\n\n
Characters<\/td>\n\u00a0Number of characters theat need to be programmed in the VRAM<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n

 <\/p>\n

Because the max7456 has NVM memory (eeprom) the writecustomercharacter routine only needs to be used one’s. The custom characters wil be left in the NVM memory even after power lost.<\/p>\n

 <\/p>\n

Downloads<\/h3>\n

Sample Bascom code<\/a> , same as below
\nMaxim’s evaluation kit software<\/a> , needed to edit the character table
\nConverter tool<\/a> , to convert the mcm file.
\nConverter manual<\/a>
\nSource code<\/a> of the converter tool in VB6<\/p>\n

And for the people who want to take it a step further, here a nice site<\/a> (In German language) where is showed how to make your own graphics.<\/p>\n

 <\/p>\n

Update:<\/strong> 2009-03-24, Bug in the Bascom code and in the Converter tool, both fixed .
\n-Bascom: Max7456 was disabled in the Writecustomcharacter sub routine, but not enabled at the end of the sub.
\n-Converter tool: loops in exportarray was counting to 56 instead of 54, removed the loops and made fixed lines.<\/p>\n

Example:<\/p>\n

'=================================================\r\n'=           MAX7456 Video overlay Demo          =\r\n'=            By EvertDekker.com 2009            =\r\n'= Created with Bascom-Avr: 1.11.9.3.001 license =\r\n'=          No copyright for private use         =\r\n'=                 Version 1.1                   =\r\n'=================================================\r\n\r\n$regfile = "m128def.DAT"\r\n$crystal = 7372800\r\n$baud = 19200\r\n$hwstack = 75\r\n$swstack = 75\r\n$framesize = 50\r\n\r\nConfig Spi = Hard , Master = Yes , Polarity = Low , Phase = 0 , Clockrate = 16 , Noss = 0       'Setup the hardware spi\r\nSpiinit                                                     'Init the spi bus\r\n\r\n'=== Dimension ===\r\nDim Temp As Byte , Lus As Byte\r\nDim Regaddr As Byte\r\nDim Regdata As Byte\r\nDim Buffer(2) As Byte\r\n\r\nDeclare Sub Initmax7456()\r\nDeclare Sub Videotext(byval Text As String , Byval Ypos As Byte , Byval Xpos As Byte)\r\nDeclare Sub Writereg(byval Regaddr As Byte , Byval Regdata As Byte)\r\nDeclare Sub Rowbrightness(byval Row As Byte , Byval Brightness As Byte)\r\nDeclare Sub Writecustomcharacter(byval Characters As Byte)\r\n\r\n'=== Const ===\r\nConst Vm0 = &H00                                            'Video mode 1\r\nConst Vm1 = &H01                                            'Video mode 2\r\nConst Hos = &H02                                            'Horizontal Offset\r\nConst Vos = &H03                                            'Vertical Offset\r\nConst Dmm = &H04                                            'Display Memory Mode\r\nConst Dmah = &H05                                           'Display Memory Address High\r\nConst Dmal = &H06                                           'Display Memory Address Low\r\nConst Dmdi = &H07                                           'Display Memory Data In\r\nConst Cmm = &H08                                            'Character Memory Mode\r\nConst Cmah = &H09                                           'Character Memory Address High\r\nConst Cmal = &H0A                                           'Character Memory Address Low\r\nConst Cmdi = &H0B                                           'Character Memory Data In\r\nConst Osdm = &H0C                                           'Osd Insertion Mux\r\nConst Osdbl = &H6C                                          'OSD Black Level\r\nConst Readreg = &H80                                        'Read register = register + &H80\r\nConst Status_read = &HA0                                    'Status register\r\nConst True = 1\r\nConst False = 0\r\n\r\n'=== Main ===\r\nInitmax7456                                                 'Init the Max7456\r\nWaitms 100\r\nWritecustomcharacter 3                                      'Write the customcharacters to the MAX7456 NVM, this has only need to be done one's. This line and data can be removed after that.\r\n\r\nDo\r\nVideotext "HELLO WORLD" , 1 , 8                             'Demo of the various possibilitys\r\nVideotext "MAX7456 Video overlay" , 3 , 3\r\nVideotext "Code written with Bascom-avr" , 4 , 0\r\nVideotext "By Evertdekker.com" , 5 , 5\r\nVideotext "{133}Flashing text{134}" , 9 , 0                 '{133}=start blinking text, {134}= stop blinking text\r\nVideotext "{131}WITH BACKGROUND{132}" , 10 , 0              '{131}=enable the background, {132}= disable the background\r\nVideotext "{135}Inverted TEXT{136}" , 11 , 0                '{135}=invert text, {136}= non-inverted text\r\nVideotext "Adjust rowbrightness" , 12 , 0\r\nVideotext "INCLUDE CUSTOM CHARS: + " , 7 , 0\r\n'Rowbrightness 12 , &B00001111                               'Change the row brightness, see the SUB for the usage discription\r\nWait 5\r\nLoop\r\nEnd\r\n\r\n'=== Subroutines===\r\nSub Initmax7456()\r\nWritereg Vm0 , &B01001100\r\n'01001000 ; 0 , 1=PAL, 00=Auto Sync, 1=Enable OSD, 0=Enable OSD always, 0=SW Reset, 0=Enable Video Buffer\r\nWritereg Vm1 , &B01111111\r\n'00010100 ; 0 = NA, 001=Background MODE Brightness 7%, 11=Blinking Time 160ms, 00=Blinking Duty Cycle BT:BT\r\nWritereg Dmm , &B01000000\r\n'01000000 ; 0=NA, 1=8bit operation,\r\nWritereg Hos , &B00011111\r\n'00011111 ; 00=NA, 00000000 = Farthest left (-32 pixels),00100000 = No horizontal offset, 00111111 = Farthest right (+31 pixels)\r\nWritereg Vos , &B00010000\r\n'00010000 ; 000=NA, 00000000 = Farthest up (+16 pixels), 00010000 = No vertical offset, 00011111 = Farthest down (-15 pixels)\r\nEnd Sub\r\n\r\nSub Videotext(byval Text As String , Byval Ypos As Byte , Byval Xpos As Byte)\r\nLocal Charcount As Byte , Tempstring As String * 1 , Tempbyte As Byte , Position As Word , Chars As Byte , Controlcharcount As Byte , Attribute As Byte\r\nControlcharcount = 0 : Attribute = 0                        'Set the local variable to zero\r\nCharcount = Len(text) - 1                                   'Count the number of characters in the string minus, because we must start at 0\r\nFor Chars = 0 To Charcount                                  'do the loop as much as there are characters\r\n Position = Ypos * 30                                       'Position where the characters must be showed 30=characters per line\r\n Position = Position + Xpos                                 'Position + the xpos\r\n Position = Position + Chars                                'Position + the charactercount that's handled this loop\r\n Position = Position - Controlcharcount                     'There was a controle charater, deduct from the charactercount because it must not be handled as real character\r\n Regdata = High(position)                                   'Put the highbyte of position in the regdatabuffer\r\n Writereg Dmah , Regdata                                    'Write the data to the register\r\n Regdata = Low(position)                                    'Put the lowbyte of position in the regdatabuffer\r\n Writereg Dmal , Regdata                                    'Write the data to the register\r\n  Tempbyte = Chars + 1                                      'Need the character position from the textstring\r\n Tempstring = Mid(text , Tempbyte , 1)                      'Take out 1 character that we need to handle now\r\n Tempbyte = Asc(tempstring)                                 'Get the ascii value of this character\r\n  If Tempbyte < 130 Then                                    'Character larger then 130 are controle characters\r\n   Tempbyte = Tempbyte - 32                                 'Max7456 character table starts at &H00, so deduct 32 to get it even with the ascii table\r\n   Regdata = Lookup(tempbyte , Characterslookup)            'Lookup the character from the datatable\r\n   Writereg Dmdi , Regdata                                  'Write the data to the DisplayMemory register\r\n  Else\r\n   Incr Controlcharcount                                    'It's a controle character, increase the counter\r\n   If Tempbyte = 131 Then Set Attribute.7                   'Set the local background bit in the character attribute\r\n   If Tempbyte = 132 Then Reset Attribute.7                 'Reset the local background bit\r\n   If Tempbyte = 133 Then Set Attribute.6                   'Set the blink bit\r\n   If Tempbyte = 134 Then Reset Attribute.6                 'Reset the blink bit\r\n   If Tempbyte = 135 Then Set Attribute.5                   'Set the inverse bit\r\n   If Tempbyte = 136 Then Reset Attribute.5                 'Reset the inverse bit\r\n  End If\r\n Regdata = High(position)                                   'Put the highbyte of position in the regdatabuffer\r\n Regdata = Regdata Or &B00000010                            'Set bit1 for the character attribute\r\n Writereg Dmah , Regdata                                    'Write the data to the register\r\n Regdata = Low(position)                                    'Put the lowbyte of position in the regdatabuffer\r\n Writereg Dmal , Regdata                                    'Write the data to the register\r\n Writereg Dmdi , Attribute                                  'Write the attribute to the DisplayMemory register\r\nNext Carcount\r\nEnd Sub\r\n\r\n\r\nSub Writecustomcharacter(byval Characters As Byte)\r\n Local Count As Byte\r\n  Restore Customcharacter                                   'Goto the begin of the data\r\n For Count = 1 To Characters                                'Number of characters that need to be programmed, must match with the characters in the data\r\n  Writereg Vm0 , &B01000100                                 'Disable osd\r\n  Read Regdata                                              'Read the first databyte, is the character to will be programmed\r\n  Writereg Cmah , Regdata                                   'Write to the register\r\n  For Lus = 0 To 53                                         'Each Character is made of 54bytes\r\n       Writereg Cmal , Lus                                  'Write the byteno of the character\r\n       Read Regdata                                         'Read the data from the datatable\r\n       Writereg Cmdi , Regdata                              'program the data in the shadowram\r\n  Next Lus\r\n  Writereg Cmm , &HA0                                       'Copy shadowram to NVram\r\n  Waitms 200                                                'Wait until copy is ready\r\n Next Count\r\n  Writereg Vm0 , &B01001100                                 'enable osd\r\nEnd Sub\r\n\r\nSub Rowbrightness(byval Row As Byte , Byval Brightness As Byte)\r\nIf Brightness > &B00001111 Then Brightness = &B00001111     'B0000xx11 Character Black Level in % of OSD white level 00 = 0% 01 = 10% 10 = 20% 11 = 30%\r\nRegaddr = &H10 + Row                                        'B000011xx Character White Level  in % of OSD white level 00 = 120%  01 = 100%  10 = 90% 11 = 80%\r\nRegdata = Brightness\r\nWritereg Regaddr , Regdata\r\nEnd Sub\r\n\r\nSub Writereg(byval Regaddr As Byte , Byval Regdata As Byte)\r\n Buffer(1) = Regaddr                                        'Put both bytes in the array\r\n Buffer(2) = Regdata\r\n Spiout Buffer(1) , 2                                       'Shift the array out the SPI\r\nEnd Sub\r\n\r\n\r\nCharacterslookup:\r\n'Convert the ascii table to the Max7456 table. (Not excist) are characters that are not in the MAX7456 table and will show a ? (&H42)\r\nData &H00                                                   '32 Space\r\nData &H42                                                   '33 !  (not excist)\r\nData &H48                                                   '34 ""\r\nData &H42                                                   '35 # (not excist)\r\nData &H42                                                   '36 $ (not excist)\r\nData &H42                                                   '37 % (not excist)\r\nData &H42                                                   '38 & (not excist)\r\nData &H47                                                   '39 '\r\nData &H3F                                                   '40 (\r\nData &H40                                                   '41 )\r\nData &H42                                                   '42 * (not excist)\r\nData &H50                                                   '43 + (not excist)\r\nData &H45                                                   '44 ,\r\nData &H49                                                   '45 -\r\nData &H41                                                   '46 .\r\nData &H47                                                   '47 \/\r\nData &H0A                                                   '48 0\r\nData &H01                                                   '49 1\r\nData &H02                                                   '50 2\r\nData &H03                                                   '51 3\r\nData &H04                                                   '52 4\r\nData &H05                                                   '53 5\r\nData &H06                                                   '54 6\r\nData &H07                                                   '55 7\r\nData &H08                                                   '56 8\r\nData &H09                                                   '57 9\r\nData &H44                                                   '58 :\r\nData &H43                                                   '59 ;\r\nData &H4A                                                   '60 <\r\nData &H42                                                   '61 = (not excist)\r\nData &H4B                                                   '62 >\r\nData &H42                                                   '63 ?\r\nData &H4C                                                   '64 @\r\nData &H0B                                                   '65 A\r\nData &H0C                                                   '66 B\r\nData &H0D                                                   '67 C\r\nData &H0E                                                   '68 D\r\nData &H0F                                                   '69 E\r\nData &H10                                                   '70 F\r\nData &H11                                                   '71 G\r\nData &H12                                                   '72 H\r\nData &H13                                                   '73 I\r\nData &H14                                                   '74 J\r\nData &H15                                                   '75 K\r\nData &H16                                                   '76 L\r\nData &H17                                                   '77 M\r\nData &H18                                                   '78 N\r\nData &H19                                                   '79 O\r\nData &H1A                                                   '80 P\r\nData &H1B                                                   '81 Q\r\nData &H1C                                                   '82 R\r\nData &H1D                                                   '83 S\r\nData &H1E                                                   '84 T\r\nData &H1F                                                   '85 U\r\nData &H20                                                   '86 V\r\nData &H21                                                   '87 W\r\nData &H22                                                   '88 X\r\nData &H23                                                   '89 Y\r\nData &H24                                                   '90 Z\r\nData &H42                                                   '91 [ (not excist)\r\nData &H42                                                   '92 \\ (not excist)\r\nData &H42                                                   '93 ] (not excist)\r\nData &H42                                                   '94 ^ (not excist)\r\nData &H42                                                   '95 Underscore (not excist)\r\nData &H42                                                   '96 ` (not excist)\r\nData &H25                                                   '97 a\r\nData &H26                                                   '98 b\r\nData &H27                                                   '99 c\r\nData &H28                                                   '100 d\r\nData &H29                                                   '101 e\r\nData &H2A                                                   '102 f\r\nData &H2B                                                   '103 g\r\nData &H2C                                                   '104 h\r\nData &H2D                                                   '105 i\r\nData &H2E                                                   '106 j\r\nData &H2F                                                   '107 k\r\nData &H30                                                   '108 l\r\nData &H31                                                   '109 m\r\nData &H32                                                   '110 n\r\nData &H33                                                   '111 o\r\nData &H34                                                   '112 p\r\nData &H35                                                   '113 q\r\nData &H36                                                   '114 r\r\nData &H37                                                   '115 s\r\nData &H38                                                   '116 t\r\nData &H39                                                   '117 u\r\nData &H3A                                                   '118 v\r\nData &H3B                                                   '119 w\r\nData &H3C                                                   '120 x\r\nData &H3D                                                   '121 y\r\nData &H3E                                                   '122 z\r\nData &H42                                                   '123 {  (not excist)\r\nData &H42                                                   '124 |  (not excist)\r\nData &H42                                                   '125 }  (not excist)\r\nData &H42                                                   '126 ~  (not excist)\r\n\r\nCustomcharacter:\r\n'Total of 3 characters in this datatable\r\nData &H50 ' Character 80\r\nData &H55, &H55, &H55, &H55, &H55, &H55, &H55, &H00\r\nData &H15, &H54, &HAA, &H85, &H52, &HAA, &HA1, &H52\r\nData &HA0, &HA8, &H52, &H85, &H28, &H02, &H80, &H41\r\nData &H2A, &HAA, &H15, &H2A, &HAA, &H15, &H42, &H80\r\nData &H55, &H2A, &HAA, &H15, &H2A, &HAA, &H01, &H02\r\nData &H85, &H28, &H52, &HA0, &HA8, &H52, &HAA, &HA1\r\nData &H54, &HAA, &H85, &H55, &H00, &H15\r\nData &H51 ' Character 81\r\nData &H55, &H55, &H55, &H55, &H55, &H55, &H55, &H55\r\nData &H55, &H55, &H56, &H55, &H55, &H56, &H55, &H55\r\nData &H56, &H55, &H6A, &HAA, &HAA, &H55, &H5A, &H55\r\nData &H55, &H66, &H55, &H55, &H66, &H55, &H55, &H96\r\nData &H55, &H55, &H96, &H55, &H56, &H56, &H55, &H59\r\nData &H56, &H55, &H65, &H56, &H55, &H55, &H56, &H55\r\nData &H55, &H5A, &H55, &H55, &H55, &H55\r\nData &H52 ' Character 82\r\nData &H55, &H55, &H55, &H55, &H55, &H55, &H55, &H55\r\nData &H55, &H55, &H59, &H55, &H55, &H59, &H55, &H55\r\nData &H59, &H55, &H6A, &HAA, &HAA, &H55, &H59, &H56\r\nData &H55, &H59, &H56, &H55, &H65, &H56, &H55, &H65\r\nData &H56, &H55, &H65, &H56, &H55, &H95, &H56, &H55\r\nData &H95, &H56, &H56, &H55, &H56, &H56, &H55, &H56\r\nData &H59, &H55, &H69, &H55, &H55, &H55<\/pre>\n","protected":false},"excerpt":{"rendered":"
The Max7456 from Maxim is a monochrome video overlay chip. With this you can overlay text and simple graphics over your PAL or NTSC video signal. You can also use it with no overlay, just like a simple monitor. Included in this sample is a tutorial how you cam make your own characters with my […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[19],"tags":[26,35,36],"class_list":["post-314","post","type-post","status-publish","format-standard","hentry","category-bascom","tag-bascom","tag-max7456","tag-video-overlay"],"_links":{"self":[{"href":"https:\/\/evertdekker.com\/wp\/index.php?rest_route=\/wp\/v2\/posts\/314","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/evertdekker.com\/wp\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/evertdekker.com\/wp\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/evertdekker.com\/wp\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/evertdekker.com\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=314"}],"version-history":[{"count":8,"href":"https:\/\/evertdekker.com\/wp\/index.php?rest_route=\/wp\/v2\/posts\/314\/revisions"}],"predecessor-version":[{"id":1840,"href":"https:\/\/evertdekker.com\/wp\/index.php?rest_route=\/wp\/v2\/posts\/314\/revisions\/1840"}],"wp:attachment":[{"href":"https:\/\/evertdekker.com\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=314"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/evertdekker.com\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=314"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/evertdekker.com\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=314"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}