I counted the number of IO Pins that I need for all the display,LEDs, buttons and switches. Without additional chips it would be: 57 input and 32 output. That’s too much, even for a Mega2560. So I was thinking about various options like… <\/p>\n
* master-slave 2 or more Atmega controllers
\n* separate controllers for in and out, each with it’s own USB
\n* shift registers (74LS164 or 74HC595) for output
\n* matrix for in & out
\n* MAX7219 for up to 64 LEDs in a matrix<\/p>\n
Here’s my plan: INPUT:<\/strong> With 4 additional chips I reduced the amount of needed IO pins from 89 to 29. When using only one microcontoller (the Atmega32 has 30 IO + TX & RX) then I can update the display quickly when I turn the rotaries without communicating with Flightgear immediately. UPDATE: * the max. output current of the 74HC595 is very limited (75mA per chip, 35mA per output) I might get away with it because I tried a red LED with 475 ohms to 5V: It is not very bright, but needs only 6,5mA this way. I counted the number of IO Pins that I need for all the display,LEDs, buttons and switches. Without additional chips it would be: 57 input and 32 output. That’s too much, even for a Mega2560. So I was thinking about various options like… * master-slave 2 or more Atmega controllers * separate controllers for in […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2,13],"tags":[],"class_list":["post-1634","post","type-post","status-publish","format-standard","hentry","category-electronics","category-fly"],"_links":{"self":[{"href":"https:\/\/blog.cipworx.org\/laserman\/wp-json\/wp\/v2\/posts\/1634","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.cipworx.org\/laserman\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.cipworx.org\/laserman\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.cipworx.org\/laserman\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.cipworx.org\/laserman\/wp-json\/wp\/v2\/comments?post=1634"}],"version-history":[{"count":4,"href":"https:\/\/blog.cipworx.org\/laserman\/wp-json\/wp\/v2\/posts\/1634\/revisions"}],"predecessor-version":[{"id":1637,"href":"https:\/\/blog.cipworx.org\/laserman\/wp-json\/wp\/v2\/posts\/1634\/revisions\/1637"}],"wp:attachment":[{"href":"https:\/\/blog.cipworx.org\/laserman\/wp-json\/wp\/v2\/media?parent=1634"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.cipworx.org\/laserman\/wp-json\/wp\/v2\/categories?post=1634"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.cipworx.org\/laserman\/wp-json\/wp\/v2\/tags?post=1634"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\nOUTPUT:<\/strong>
\nI use 2 shift-register ICs for all the Data & CE lines of the alphanumeric display
\nand connect A0, A1 and WR of the display direct to the controller.
\nI use a MAX7219 for all LEDs.
\nResult: a total of 8 output pins of the microcontroller.<\/p>\n
\nI want to connect all 6 rotaray encoders directly to the microcontroller to get the best
\ntiming, so 12 input lines for that.
\nFor the remaining buttons & switches I use a 8×6 matrix (with 45 diodes)
\nTo scan the 8 rows I want to use a 1-out-of-8 (3bit) binary decoder chip
\nResult: a total of 21 pins used for input.<\/p>\n
\nWith the MAX7219 I have the option of adding many more LEDs If I want and on the input side I can still add 3 more switches or buttons to the matrix.<\/p>\n
\nI hope that USB serial is enough for everything that I want and there is no need for USB HID for this device.<\/p>\n
\nYesterday I had the good(?) idea to use 4 shift registers instead of
\n2 shift registers + MAX7219. So I started to build a board with 4 x 74HC595 with all 32 outputs going to a 34-pin connector where I’ll plug in a ribbon cable. After finishig my board it came to my mind again what knew already but did forget: <\/p>\n
\n* I’ll need a resistor for every LED – (which is not the case with the MAX7219)<\/p>\n
\nI can’t use low current LEDs because they are all integrated in the buttons.<\/p>\n","protected":false},"excerpt":{"rendered":"