Simultaneous PIC reset

[Nigel Goodwin]

As you're only talking about two devices, it's FAR simpler to use simple RS232 between the two devices, I2C is for connecting multiple devices to the same bus.

 

[Krumlink]

As you're only talking about two devices, it's FAR simpler to use simple RS232 between the two devices, I2C is for connecting multiple devices to the same bus.

I know it would be, but it is reserved for PC to MCU communication. I have been working on a rs232 communication program in python for this reason, therefore I would have to use something else, e.g. SPI, I2C, PSP, etc.

 

[David James]

I know it would be, but it is reserved for PC to MCU communication.

Couldn't you use software RS232 rather than the hardward UART?

 

[Krumlink]

USART to be specific. I was going to use I2C for PIC to PIC and USART for PIC to Computer. I could use software USART, but I will use I2C or SPI.

 

[arhi]

Hey krumlink, I made a "lcd + lcd + .. " i2c slave while back. You can get it from here. There is both HW and SW implementation for the slave device that run LCD (2x16)

The HW i2c implementation uses 16F690 and SW i2c implementation uses 16F628A. You have full sources available so you can easy change the source to apart from writing to LCD only set some outputs and read some inputs .. with 690 I was using 2 ADC inputs and few outputs ... works like a charm

 

[Papabravo]

After some more consideration of your earlier request, I think you might consider a chip known as an analog switch. One side goes to MCLR and a pullup, while the other side goes to GND. The switches are normally open so that MCLR sees only the pullup. Now for the control signals you can control them together for normal operation, or separately for programming.

 

[Krumlink]

After some more consideration of your earlier request, I think you might consider a chip known as an analog switch. One side goes to MCLR and a pullup, while the other side goes to GND. The switches are normally open so that MCLR sees only the pullup. Now for the control signals you can control them together for normal operation, or separately for programming.

Thank you for considering my OP, but Ive already wired in a standard reset switch. I do not need simultaneous resetting, as the Master will be handing most code, and the slave will be handling non vital processes, e.g. LED's, LCD, etc.

 

[Papabravo]

Still an analog switch comes in handy on occasion.

 

[Nigel Goodwin]

Still an analog switch comes in handy on occasion.

Yes they do, but it's a poor choice for the original question, two transistors would be far better - but it's totally not required anyway.

 

[Krumlink]

I'm going to use I2C, because it requires fewer I/O pins. If I read correctly I need 10k pullup resistors on SCL and SDO?

 

[Nigel Goodwin]

The pullup resistor values aren't any fixed value, they can vary greatly - for longer PCB tracks (bearing in mind I2C is for connecting multiple IC's on large PCB's) you should use lower values, to overcome the track capacitance.

10K should be fine for you, as would 22K, 1K - it's not at all critical.

 

[Krumlink]

The pullup resistor values aren't any fixed value, they can vary greatly - for longer PCB tracks (bearing in mind I2C is for connecting multiple IC's on large PCB's) you should use lower values, to overcome the track capacitance.

10K should be fine for you, as would 22K, 1K - it's not at all critical.

Yes, I've revised the schematic and now I have 2 slave I2C's to better incorporate multiple devices.

 

[arhi]

depending how big the PCB is .. (how long the i2c bus is) ..you need to use lower value ... 4k7 is my pullup of choice .. works every time for all "normal size" boards ... as for the lcd .. I made few of those modules with 16F690 with LCD + additional ports that I use in whole bunch of projects.. I also have idea to make the LCD module "detachable" for some projects...