What is the best signal interface for PC ?

[marconi]

Not read yet what you posted recently but this is the transistor and resistor hardware to interpret the 16 bit data word I mentioned earlier. The pnp transistor is a BC557B.

 

[_q12x_]

You can use NPN as well. Depends what you have more.
Also dont forget each resistor to each matrix board pin !!! You should include resistors for each pin, in your circuit. 1k is good enough.
Also very important, make your circuit as logical and simple to follow as possible, as much intuitive you can make it. You really have to put your neurons to work for this part. I know for sure. It will pay up for you in the near future and for others that are reading your circuit.

 

[marconi]

Yes. I missed off the current limiting resistor in each of the pnp transistor collector - line ( row) paths.

 

[_q12x_]

This led matrix pin number assignment is pretty much like a code.
All that I did was to 'decode' it into a human easy to understand and intuitive way of dialing.
If you remember in WW2 - the german made 'Enigma Machine' ? Pretty cool device. This was pretty similar to that. In my mind at least.
You basically have to link 7 positive (+5V) pins that will represent your lines and 5 negative (0V) pins that will represent your columns. All passing through transistors (whatever they are, doesn't matter) to be able to command each pin separately from your future hardware code.
You know what is interesting and relatively fast? to put buttons and press them all at once to get ...well, only 1 line at a time. pretty much like I did in my code at very low fv. Or simple mechanical switches !!! So --12-- in total.

 

[marconi]

You have it. The column Cn and line Ln (my row Rn) bits in the 16 bit data word at the output of the MCP2017 select the column and line transistor switches as on or off. This is done column by column as you see in my earlier video with all Ln set to logic O so all 7 LEDs in a column light up as a test.

 

[marconi]

q12x good afternoon to Romania. I have attached a short video of the eeprom programmer I made today which demonstrates the first five memory locations loaded with different test patterns for the 8 bit Line (my Row) data words - only 7 bits actually used. The top set of dip switches sets the data word to be stored and the lower set selects the address to store the data word. The small black button generates a pulse to tell the eeprom to store the data as detailed on the dip switches. I will build next some sequential logic counters to address the eeprom to retrieve a particular group of 5 L/R data words to drive the 7 x 5 LED display and produce the image I want. In my case the 16 letters a through to n for the earlier Gray Code project so there will be 16 groups of L/R data words.

The test patterns would display the third attachment - note drawn for 8 lines/rows.

 

[Jim_Mc]

Hi there,

Looks like you're using a single ATMEGA328 for each 16 LEDs? This is completely unnecessary. If the only requirement is to drive multiple LEDs in a sequence, then you could do this using a shift register, like in this example:

Shift Registers - 74HC595 & 74HC165 with Arduino

Learn to use the 74HC595 and 74HC156 shift registers to add extra input and output ports to your Arduino, then use them to build a fancy LED light display!

dronebotworkshop.com

You can get multiple shift registers, or shift registers with more parallel output pins to drive the number of LEDs which you need.

I believe you can even chain them to get more output.

This will be a) cheaper and b) more energy efficient than powering multiple 328p's.

 

[_q12x_]

I reinstalled back my arduino Uno and everything is working as before.
But in my latest program that I made, I can obtain a diagonal line on a Led Dot Matrix as a test program, but its refresh rate can not be lower than 1ms as arduino is restricting. MCP chip is minimum 100kHz (actually has higher values specified) which means 10μs per cycle.
- Do anyone know how to lower arduino fv to μs instead of ms ?
In the movie here I present using it's internal fuction
delay(dly);
which is a ms function, I read about it and I get that. I tried also its other function as well, named
delayMicroseconds(dly);
and the result is exactly as the delay(dly); in ms and not under 1ms, to it's promoted μs.
This is a 2min video where I explain the entire problem, please watch it.
Thank you.

 

[marconi]

5x7 DOT Matrix - https://fontstruct.com/fontstructions/show/847768/5x7_dot_matrix

Today, I programmed the eeprom with the 7 x 5 fonts for the capital letters A to P. Now I will look at your latest video.

My initial reaction to the word 'delay' is that you may be using the wrong command. A delay is just that - it does something later than demanded. This may be your problem because the delay is slowing things down such as data transfers.. eg: The data transfers occur every 10 microseconds (say) and then you delay each transfer by 10milli seconds. The delay will dominate. But as I say I am not at all versed in the arduino you are using.

For most people a refresh rate of 50 to 100Hz fools the eye and brain to see a flicker free image as in a conventional TV picture - but modern TV's may do something different these days.

You could average over time the output in software to remove the flicker to make the output virtually constant until there is a change in output. Write a new sub-routine which takes your current sub-routines output as its input and produces an output which is flicker-free.

 

[_q12x_]

For most people a refresh rate of 50 to 100Hz fools the eye and brain to see a flicker free image as in a conventional TV picture - but modern TV's may do something different these days.

100Hz not 100kHz! - VERY Interesting that you mention this! This is helpful. So my 1ms delay in code might not be a real 1ms at all. The speed in reality is probably somewhere at 20Hz now that I think about it. Hmmmm... very intriguing. They definitely have some issues on their I2C pins on that arduino board.
I just google a bit and I find and confirm with: "most humans can't easily distinguish individual frames at 30 hz."
The visible fast flickering is under 30Hz !
So the SCL pin from arduino is simply under 30Hz and not even close to 1ms which is 1000Hz. Hmmm, very interesting.