Hi.
I am working on something, and to that i need more than one MCU.
And no, i can not use a "bigger" MCU,
The 4 SLAVE MCU will just recieve data( Each Second ) , but i still believe i need both RX and TX. ? or are i wrong ?

I Know i also could do a RING based config like this next



But i think that will challange me more,
-----------------------------------------------
Also i have some LED i need to control.
When activating INPUT 1 then 12 first LED should be ON.,
When activating INPUT 2 the 12 first and 8 next should be ON.
When activating INPUT 3 the all (25) should be ON.

Is that a design that would work, ?

 

There is more than one way to skin a cat.
I do it all the time, not skin a cat, but interface multiple MCUs.

These are the known ways of wiring MCUs together:

1. UART
2. SPI
3. SCI
4. I2C
5. 1-Wire
6. Parallel

It would help if you told us what you are attempting to do.

 

Ok. some more info,
I will do a full size clock, D60 Cm. each hand concist of 25 LED, Like i have drawn, in last picture,
When just 12 on = Hour Hand.
When 20 on = Minute Hand
When all 25 is on = Second Hand.

I will divide it into 4 boards(30*30 cm ) and a MASTER PCB. like 10*10 cm onto back middle.

The comm will be from the MASTER MCU and out the the 4 others that controls all the LEDS.
If i use just 1 MCU i would need a lot of multiplexing and a lot of wires to central board.
Remember it's 180 Outputs.
This way i will only use 15+3 + TX+RX. = 20 IO p MCU,
And the Master MCU could be a even smaller one, just need RX-TX , Xtal input ,and 2-3 input to set time.

Or maybe an other way to approch this ?

 

A possible alternative is to use shift-register chips in a daisy-chain for outputs using one controller. A single SPI port can easily handle 180 outputs.
https://www.instructables.com/id/3-Arduino-pins-to-24-output-pins/
https://www.marginallyclever.com/2017/02/daisy-chain-74hc595n-shift-registers/

 

Yes, but again i will only use Microchips PIC16F series and not that Ardridododo .
But if you think it can be done with PIC16F then i will try to work with this, But this will give me 22,5 Shift registers.
And they are expensive, can buy allmost 100 Mcu for that price

 

If you don't have SPI hardware you can "bit banging" the shift registers. I would use something with SPI hardware.

The SN74HC595N is not that expensive.
https://www.mouser.com/ProductDetail/Texas-Instruments/SN74HC595N?qs=IEl3ej0IqwBTHkYa8XPoMQ==&gclid=CjwKCAjwvZv0BRA8EiwAD9T2VZjELBHL-h2usztK_74kznlMFxBe18hWWLt2Tgt_bid_Kw_FCgDmoRoCxOQQAvD_BwE

 

Question , can i connect the MCU like i did, and will it work ?

Could use all that 24 74HC595. and learn how to use SPI.
Just think that these MCU was easyer,

 

Question , can i connect the MCU like i did, and will it work ?

Could use all that 24 74HC595. and learn how to use SPI.
Just think that these MCU was easyer,

You did ask for other ways to approach this. Sure, you can use your MCU master/slave bus configuration or daisy-chain but you will need some way to address each controller individually like using 9-bit serial transfers for node addressing or encoding addressing in the data stream with extra bits using a prefix header byte. In the end what's easier is up to you but I think you will find that the extra controllers will be programmed to basically emulate shift-registers in this application anyway.

 

As I have said, I have done this before.
With one master and N slaves I would choose one-wire phase encoded signalling. I did this with Microchip PIC16C554, 100k bits per second with no external xtal, no UART.

 

I did 15 74hc595 running from a pic16.. very easily

 

I just reread the application. Ok, you do not need any slave MCUs.
Simply one long shift register as outlined in post #10.

 

As I have said, I have done this before.
With one master and N slaves I would choose one-wire phase encoded signalling. I did this with Microchip PIC16C554, 100k bits per second with no external xtal, no UART.

Hi again

If comm is just from master to slave, will it the be possible or do i also need the RX signal ?(on master)
Just connect TX from master to all 4 slaves RX ?

 

Yes, you can do that. But you need to embed a slave ID in the message.