Just like in old-fashioned cathode ray tv sets, the 'screen' is scanned row by row.During the time each row is processed it essentially boils down to a counter running, against which the desired brightness of each colour is compared. Once the counter is greater than said value(s), the led is turned off. This produces a square PWM signal. By changing the duty-cycle the base colours are changed. The static image relies on persistence of vision. The C-code is on my blog.
@zupnikal It's an 8IN 8OUT style keyboard matrix, so it shouldn't be too bad. It does have a serial interface, but the type protocol is ridiculous. As best I can tell from probing, it has three 8-bit reg's for serial control. Two are for stepper drivers (yes, you have to program the freakin' stepper sequence externally) and the last reg is for the daisy wheel. Also, the last bit of the register is the strike bit, so the characters are 7-bit. Which means I no ASCII.
@mrmikerotch: So if you use it the normal way it advances by 1 letter automatically, if you send data over the wire you need to send the actual high/low sequence for the coils? That's hilarious.
@zupnikal I have been doing some more poking around, and I'm starting to think that the "interface" is multiplexing the stepper driver for the carriage with the letter selection as binary. When I took the first three bits and cycled them in phase, I was able to move the carriage back and forth, and the next four are the first four bits for letter selection. I thought that the last line was a "strike" pulse, but now I think it is a multiplex clock.
cont... I think it may have been made this way to avoid using some more expensive chips. Any '80's guys out there? Also, I totally noobed myself back there. When I first said serial interface, I meant parallel. Sorry for any confusion.
Sure. As I can't post links in comments, just visit my blog. The link is on my youtube profile page. There you'll find schematics, code and the layout files (gerber format). You want to make sure you use the latest versions of it.
If you want to display video on it, you need a real computer to process the video signal and scale it down to 8x8 and send it over. This can be done with the "processing" language or even in Perl. At least on linux. I've written a short article on instructables about that.
This appears to be very impressive. But did it occur to you that we might want some audio of you explaining what you are showing us? The jumpers at the end, anything?
Nice work. The fabbed board looks great. But the video is disappointing.
It would be a lot easier to do the audio track afterwards, but that's a real pain in the ... with linux. Moving my ahdns, thinking and talking at the same time just doesn't work.
What's also freaking me out is that youtube block comments sometimes and nobody knows why. Doesn't mark the stuff that's "invalid", but just blocks the whole thing.
The FTDI connector has the hardware UART pins on it. Headers on the backside expose PORTC and PORTD. The I²C and also the RX/TX lines are among them, so the "wire" library should work also. And there is always the "NewSoftSerial" library.
May i ask, how you program the colour change on rgb leds?
mikey6879 7 months ago
@mikey6879: by hand ;-)
Just like in old-fashioned cathode ray tv sets, the 'screen' is scanned row by row.During the time each row is processed it essentially boils down to a counter running, against which the desired brightness of each colour is compared. Once the counter is greater than said value(s), the led is turned off. This produces a square PWM signal. By changing the duty-cycle the base colours are changed. The static image relies on persistence of vision. The C-code is on my blog.
zupnikal 7 months ago
Wikkid shield!
horlacsd 1 year ago
I wonder if I could use something like that to drive an electronic typewriter...
mrmikerotch 1 year ago
@mrmikerotch: Maybe. Simulating key presses sound like a lot of wires, but should work. If you're lucky, it's got a serial interface.
zupnikal 1 year ago
@zupnikal It's an 8IN 8OUT style keyboard matrix, so it shouldn't be too bad. It does have a serial interface, but the type protocol is ridiculous. As best I can tell from probing, it has three 8-bit reg's for serial control. Two are for stepper drivers (yes, you have to program the freakin' stepper sequence externally) and the last reg is for the daisy wheel. Also, the last bit of the register is the strike bit, so the characters are 7-bit. Which means I no ASCII.
mrmikerotch 1 year ago
@mrmikerotch: So if you use it the normal way it advances by 1 letter automatically, if you send data over the wire you need to send the actual high/low sequence for the coils? That's hilarious.
zupnikal 1 year ago
@zupnikal I have been doing some more poking around, and I'm starting to think that the "interface" is multiplexing the stepper driver for the carriage with the letter selection as binary. When I took the first three bits and cycled them in phase, I was able to move the carriage back and forth, and the next four are the first four bits for letter selection. I thought that the last line was a "strike" pulse, but now I think it is a multiplex clock.
mrmikerotch 1 year ago
cont... I think it may have been made this way to avoid using some more expensive chips. Any '80's guys out there? Also, I totally noobed myself back there. When I first said serial interface, I meant parallel. Sorry for any confusion.
mrmikerotch 1 year ago
great project
daxweb 2 years ago
Sure. As I can't post links in comments, just visit my blog. The link is on my youtube profile page. There you'll find schematics, code and the layout files (gerber format). You want to make sure you use the latest versions of it.
zupnikal 2 years ago
can i connect a ps2 or another device that has an RGB out to it?
uut0 2 years ago
No. You can connect to it with a serial interface (USB to TTL serial) or I2C. The cpu is way too slow for analyzing video signals.
zupnikal 2 years ago
If you want to display video on it, you need a real computer to process the video signal and scale it down to 8x8 and send it over. This can be done with the "processing" language or even in Perl. At least on linux. I've written a short article on instructables about that.
zupnikal 2 years ago
This appears to be very impressive. But did it occur to you that we might want some audio of you explaining what you are showing us? The jumpers at the end, anything?
Nice work. The fabbed board looks great. But the video is disappointing.
monkey505boy 2 years ago
I feel your pain, but I'm just too shy.
zupnikal 2 years ago
It would be a lot easier to do the audio track afterwards, but that's a real pain in the ... with linux. Moving my ahdns, thinking and talking at the same time just doesn't work.
What's also freaking me out is that youtube block comments sometimes and nobody knows why. Doesn't mark the stuff that's "invalid", but just blocks the whole thing.
zupnikal 2 years ago
Sure.
The FTDI connector has the hardware UART pins on it. Headers on the backside expose PORTC and PORTD. The I²C and also the RX/TX lines are among them, so the "wire" library should work also. And there is always the "NewSoftSerial" library.
zupnikal 2 years ago
Hi Robert,
einfach toll :-)
Gruss Helmut
friedbert13 2 years ago