Need CRC for RF PIC2PIC Bit arrayed interface

[SteveB]

Thx, I will try the shifting.
I choosed the Max 148 ADC becouse its free
You can order sample www.maxim-ic.com
The other reason:
I want minimal pin usage for SPI, so the rest of the PIC pins
can be used for Switches.

Free is a GOOD PRICE. Here is another way to look at it:

MAX 148 = 20 pin
PIC16F168A = 18 Pins
16 IO pins (-2 if using an Ext OSC)
(-4 for SPI Interface)
= 38 Pins for 12 usable IO Pins (or 10 with ext OSC)

Pic18F2620 = 28 Pins
24 IO pins (-2 if using an Ext OSC)
10 ADC (leaves 14 IO PINS remaining)
= 28 Pins for 14 usable IO Pins (or 12 with ext OSC)

Just my 2 cents,
Steve

[mrx23]

I'll choose one of these:
PIC16F685
PIC16F689
PIC16F785
they are very cheap, about $2 of each
12 number of 10bit ADC onboard.
4096 words code sp (does the newest PicBasicPro support above 2k codespace?)
18 I/o lines (-used ADC)

Shiftin/out for SPI are VERY slow: 50KHz clk out
the Max148 supports 2Mhz clk

Here is a very good CRC8 describe with easy example
http://pdfserv.maxim-ic.com/en/an/AN...h=%22an3749%22
Both loop and table driven CRC's, its easy to convert to CRC16.

About supply:
My plean is to use a zener based (and shunt transistor) regulator, like here:
http://www.satcure-focus.com/tutor/page5.htm

itt'll cut higher voltages than 5V from battery, and the PIC's BODEN will
restart continuously when the battery is to low.
The supply will ONLY power the PIC (very max ~1W), from 7.2V battery.

The same'll be on the receiver side, but it will ha low volt detect
that will shut down the motor signal.
(an internal comparator feeded by an internal reference ~1V,
and voltage divided battery input 1:4)
That will stop the motor when battery is under 4V.

Is my plean correct?