64 pin PIC microcontroller suggestion

Hi edaboard, I am planning to build another application but this time it is a bigger one. I'm having problems about choosing the microcontroller that could/must be used. I'll be controlling 20 LEDs, 1 LCD display and 20 push buttons. ROM, RAM and processor speed here is critical so I'll choose the highest one. I have PICKIT3 with me and MPLAB. 40 pin microcontroller is not enough considering the use of multiplexing so my next resort is a microcontroller which has higher pin counts. I just don't know if I have to use dspic's, pic24's or pic30's. Any microcontroller suggestion that is easy to start with and typically used one? Btw, my previous microcontroller was a PIC18. I already thought of using two PIC18 but I think it would consume much processing time making the application slow. I've used the PIC18 for already a year so I want this time to explore another PIC family.

Regards,

lloyd

multiplex your pins, you will need less...
here is an example of multiplexing leds and buttons : **broken link removed**

also attached an application note from parallax enplaining the multiplexing process

lloydi12345 said:

I am planning to build another application but this time it is a bigger one. I'm having problems about choosing the microcontroller that could/must be used. I'll be controlling 20 LEDs, 1 LCD display and 20 push buttons. ROM, RAM and processor speed here is critical so I'll choose the highest one. I have PICKIT3 with me and MPLAB. 40 pin microcontroller is not enough considering the use of multiplexing so my next resort is a microcontroller which has higher pin counts. I just don't know if I have to use dspic's, pic24's or pic30's. Any microcontroller suggestion that is easy to start with and typically used one? Btw, my previous microcontroller was a PIC18. I already thought of using two PIC18 but I think it would consume much processing time making the application slow. I've used the PIC18 for already a year so I want this time to explore another PIC family.

Click to expand...

There are numerous options available in both the PIC18 and PIC24 series. If you want to make a jump to the next level of PICs then consider the PIC24 series, they are 16-bit vs the PIC18 8-bit devices.

Make a list of the project requirements, pin count, peripheral modules, operating voltage, etc and use the following to select a viable device:

**broken link removed**

Microchip Advanced Parts Selector

BigDog

lloydi12345 said:

processor speed here is critical so I'll choose the highest one.

Click to expand...

You do not give any idea of what clock speed you are thinking of or what its purpose is.
Generally find most folk over estimate the speed they really need.

Moving to a 64 or 80 pin chip means soldering smd parts, are you happy with that - they can be a pain and removal is not easy.
Also most ,if not all, of the 64 pin + chips only have a few ports capable of driving a led directly, unlike a 40 pin 18F.

Don't forget a chips total current handling, between 200-350ma depending of type, with 20 leds you could well overload one chip.
You could use driver chips like the ULN2803, but would sharing the load over 2 18Fs be simpler ??

Sorry I forgot to include that I'll be using 3 extra port pins to drive relays and 1 pin to read analog voltage

Kripton2035 said:

multiplex your pins, you will need less...
here is an example of multiplexing leds and buttons : **broken link removed**

also attached an application note from parallax enplaining the multiplexing process

Click to expand...

I tried calculating the pins that will be used and it would be 9pins(5x4 for 20 push buttons) + 11pins(Controlling LCD) + 11pins(controlling 20 LEDs using multiplexing like driving 5x7ledmatrix) + 4pins (I/O) = 35pins (I/O) so it is not enough for PIC18's 33pins for I/O (40pin Mcu-1mclr pin-4vdd/vss pins-2osc pins).

bigdogguru said:

There are numerous options available in both the PIC18 and PIC24 series. If you want to make a jump to the next level of PICs then consider the PIC24 series, they are 16-bit vs the PIC18 8-bit devices.

Make a list of the project requirements, pin count, peripheral modules, operating voltage, etc and use the following to select a viable device:

**broken link removed**

Microchip Advanced Parts Selector

BigDog

Click to expand...

Those applications are really helpful but I guess I'll not be using them for now since the fancy features like I2C,SPI,CAN,etc. aren't really critical to my application. Just 10bit-ADC, at least 40 I/O pins, well sorta things like what PIC18F4620 at least has like the program and data memory and speed. I think it would be better if I'll use frequently used microcontroller on the web so that if ever I would have problem, I'll just google it or seek advice from the person expert on that specific mcu. This would significantly speed up my developing and debugging time.

wp100 said:

You do not give any idea of what clock speed you are thinking of or what its purpose is.
Generally find most folk over estimate the speed they really need.

Moving to a 64 or 80 pin chip means soldering smd parts, are you happy with that - they can be a pain and removal is not easy.
Also most ,if not all, of the 64 pin + chips only have a few ports capable of driving a led directly, unlike a 40 pin 18F.

Don't forget a chips total current handling, between 200-350ma depending of type, with 20 leds you could well overload one chip.
You could use driver chips like the ULN2803, but would sharing the load over 2 18Fs be simpler ??

Click to expand...

Well, I guess you're right I'm again overestimating everything about the processor speed. I'll just use 8Mhz on its external oscillator. Yeah, I already considered the tough work I'll encounter soldering SMD's but this would at least take my fear off for soldering this kind of devices It would be another exploration if I would be able to use 64pin 16bit MCUs and guess this will be a tough but fun challenge. I'll also use IC's with transistors to control the LEDs because SMD devices surely can't handle the current.

I have in my mind dspic30f6014 if you have suggestion for specific dspic or pic24 please let me know. Thanks

Thanks everyone for your responses

lloyd

lloydi12345 said:

Sorry I forgot to include that I'll be using 3 extra port pins to drive relays and 1 pin to read analog voltage



I tried calculating the pins that will be used and it would be 9pins(5x4 for 20 push buttons) + 11pins(Controlling LCD) + 11pins(controlling 20 LEDs using multiplexing like driving 5x7ledmatrix) + 4pins (I/O) = 35pins (I/O) so it is not enough for PIC18's 33pins for I/O (40pin Mcu-1mclr pin-4vdd/vss pins-2osc pins).

Thanks everyone for your responses

lloyd

Click to expand...

you can drive a lcd in 4 bits mode, then it's only 7 pins (R/S - R/W - E - D4-D7) instead of 11 as you say
so total 31 I/O pins fits your pic18...
you can also use an analog entry with resistors to put easyly 5 buttons on a pin. that's only 4 analog input pins for your keyboard
better stay in pic18 with low pin counts. as other member suggests, 64 and 80 pins pics are more difficult to soldier ...
you can also use one external ic to extend peripheral pins like a pcf8574, is't enought and so you don't need to go to bigger pic.
good luck.