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Forum Index : Microcontroller and PC projects : Micromite interrupt composite video??
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halldave Senior Member  Joined: 04/05/2014 Location: AustraliaPosts: 121 |
I know the maximite and colour Maximite created video out with good VGA etc. is it possible to create a simple interupt driven library for generating composite video out of the Micromite, or is this beyond the capability of the PIC32 and the way in which MMbasic uses the interrupts something similar to the link below that can be hacked for Arduino https://code.google.com/p/arduino-tvout/ |
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| halldave Senior Member Joined: 04/05/2014 Location: AustraliaPosts: 121 |
or examples like this that are PIC based, has anyone tried http://www.micro-examples.com/public/microex-navig/doc/089-p ic-pal-tv.html#2 |
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
I'm pretty sure that the MM can generate composite video instead of the VGA - but not both at the same time. Will check. I know that the monochrome MM could have composite video out, and I think that the MM can too, but only in one colour as composite colour video is too much of a hurdle I think.(within that chip, anyway). EDIT: Yes, the colour MM can also output composite video, but only in one colour. EDIT: There is also TELLYMATE, if you want to generate B/W composite video from any mocrocontroller serial commands - very much like your 2nd link.... TELLYMATE Smoke makes things work. When the smoke gets out, it stops! |
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| halldave Senior Member Joined: 04/05/2014 Location: AustraliaPosts: 121 |
Would the pinouts be the same as Geoff's composite, and then would MMBasic as supplied on the Micromite drive it or would it need mods to the source and a recompile http://geoffg.net/Images/Maximite/Composite%20Video.png |
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| halldave Senior Member Joined: 04/05/2014 Location: AustraliaPosts: 121 |
Wow thanks the TELLYMATE looks promising and easy to drive, might investigate this a little more thanks for the prompt reply regards David |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
Hi - yes, the composite video is generated directly and internally within the PIC32 by MMBasic, so instead of the VGA connector, you just use an RCA lead and plug into the composite video input on your TV set. I have used the TellyMate quite a bit, and yes you are right - it is dead easy to use, and completely open so anyone can build it. I have several home-made spares - PM me with address if you would like a programmed TellyMate to play with. Smoke makes things work. When the smoke gets out, it stops! |
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| robert.rozee Guru  Joined: 31/12/2012 Location: New ZealandPosts: 2442 |
everyone seems to have missed your main question. the MaxiMite family of single-chip computers (32MX695 processor) run at twice the speed of the MicroMite, have four times as much flash memory (ROM) and four times as much RAM. The processor that is the MaxiMite has 4 SPI channels and approaching 100 I/O pins, while the Micromite has only 2 SPI channels with less than 20 available I/O pins. to generate VGA colour video, the MaxiMite makes use of THREE (of its four) SPI channels configured in a rather creative way. The method of generating the video precludes using a character generator ROM, and so all video modes have to be bitmapped, taking up large portions of the available RAM. and finally, 8 I/O pins are used for video purposes. the MicroMite (32MX150 processor) only has two SPI channels, precluding colour VGA video from the start. with 32k of RAM available, a monochrome (single colour) video mode of 480x432 pixels would use up 26k of this RAM. this is more than the amount of free RAM available in the MicroMite (remember - the interpreter uses 12k internally). the bottom line is that the MicroMite/32MX150 has insufficient resources available to generate video and run the BASIC interpreter at the same time. even just generating a monochrome video image would stretch the hardware. while there are some tricks that can be used to reduce the RAM requirements, such tricks would pretty much preclude running BASIC as well. rob :-) |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 4044 |
What a great site! Thanks for that. John |
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| WhiteWizzard Guru Joined: 05/04/2013 Location: United KingdomPosts: 2944 |
halldave, Another very low cost solution is to wait for Part 3 of Geoff's Silicon Chip Magazine series (out in one months time). This will be featuring an ASCII Video Terminal which effectively adds a keyboard and also Video (VGA and Composite) to a MicroMite. Note it is mono output only so you won't be able to use escape code sequences to generate colour (as is possible with a MicroMite connected to TeraTerm). WW |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
He's in your neck of the woods, so I'm surprised you had not heard of him - but then - United Kingdom is rather a large place..... 
Smoke makes things work. When the smoke gets out, it stops! |
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| halldave Senior Member Joined: 04/05/2014 Location: AustraliaPosts: 121 |
Wow, Part 2, still hasn't hit the streets and already your dangling a carrot with part 3 goodies. I'm going to have a crack at the tellymate as per grogster's suggestion as the escape sequences and the code-page 437 character set is reminiscent of the characters I had to work with when gwbasic and qb45 was around. regards David |
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Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3292 |
If you want an early taste of the ASCII Video Terminal (a video display from a PIC43MX250) there is this preliminary web page: http://geoffg.net/terminal.html Geoff Geoff Graham - http://geoffg.net |
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| halldave Senior Member Joined: 04/05/2014 Location: AustraliaPosts: 121 |
Geoff, you have been busy. I think ill go order some boards / chips today, so they can be in my hot little hands in time for July Silicon Chip edition thanks for the heads up regards David |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
Yes, I had forgotten about Geoff's latest beast. It's hard to keep up with the man!!!!! 
I will be building one of these too, to play with. Features list etc, is impressive for a single-chip design.  Smoke makes things work. When the smoke gets out, it stops! |
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Zonker Guru Joined: 18/08/2012 Location: United StatesPosts: 767 |
Nice work..! I really like the PCB layout  Big "old school parts", logical parts layout, makes a good beginner project for the first time builder.. Perfect... It kind of reminds me of the original MM board work... Geoff...  Did you create this..?
Somebody needs a big tip of the hat..!!  |
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| Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3292 |
Yes, all my own work. It is kind of creepy seeing it work. In my early days I worked with UNIX computers where ASCII terminals were everywhere and the VT100 was king of the hill (and one of the most expensive). And now all the works are inside a single $3.80 chip. Geoff Geoff Graham - http://geoffg.net |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
Indeed...... I used to replace VT100 terminal's semi-regularily. They were WYSE-100's. Not counting the screen part(which was always the bit that failed or had such bad burn-in, that it made reading the REAL text hard!), the actual terminal box was about twice the size of an A4 sheet of paper, and was FULL of chips. Amazing what we can do now with microcontrollers, it really is. Smoke makes things work. When the smoke gets out, it stops! |
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| halldave Senior Member Joined: 04/05/2014 Location: AustraliaPosts: 121 |
RS Components are quoting $5.98AUD per chip, where has them at $3.80? MCU,PIC32MX250,40MHZ,128KB Flash,SPDIP28 RS Stock No. 768-0836 Brand Microchip Mfr. Part No. PIC32MX250F128B-I/SP RoHS status Compliant regards David |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
Microchip Direct - about $15 courier to New Zealand, so I guess you would be about the same price. Will pop up link as soon as I find it.... Here it is. MAKE SURE YOU SCROLL DOWN AND ORDER THE SPDIP ONE!!! It is called PIC32MX250F128B-50I/SP Microchip make most of their MCU's in several different packages, so you need the DIL one or it won't fit Geoff's PCB. Remember though, that $4.05 price is in US dollars. By the time you convert that to Australian dollars, six bucks is probably about right. Also depends on what price it will cost you in freight to get them locally, vs overseas. The $3.80 figure comes from the MicroMite chip price I seem to recall, but it is probably a little cheaper cos it does not have(nor need) the USB interface that the 250's have. Smoke makes things work. When the smoke gets out, it stops! |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
Opps - below the 50I/SP is the standard I/SP which is the 40MHz part, and IS $3.80 My mistake. Smoke makes things work. When the smoke gets out, it stops! |
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