For a recent project I experimented with alternatives to the very low end PIC 10LF322 chips. I made a small prototype board with the PIC 12LF1822 to perform some tests.
The 6-pin header directly connects to the PICkit 3 in-circuit debugger/programmer.
PIC12LF1822 Board with LED
The board is programmed in JAL [1], a medium high level language. JALv2 is a rewrite of Wouter van Ooijen’s famous Just Another Language. Besides the JAL language compiler, there is a library of support functions and samples for many PIC devices [2].
Here is a non-trivial code example of a “blink the LED” routine for the Microchip 12LF1822 device:
-- -- ----------------------------------------------------------------------------------- -- Title: Blink-a-led of the Microchip pic12lf1822 - WDT sleep version -- -- Author: Karin Willers, Copyright (c) 2011, all rights reserved. -- -- Compiler: 2.4o -- -- Released under the BSD license (http://www.opensource.org/licenses/bsd-license.php) -- -- Description: -- Sample blink-a-led program for Microchip PIC12lf1822 -- Blink with WDT sleep -- -- ----------------------------------------------------------------------------------- -- include 12lf1822 -- target PICmicro -- This program uses the internal oscillator pragma target clock 1_000_000 -- oscillator frequency -- configuration memory settings (fuses) pragma target OSC INTOSC_NOCLKOUT -- internal oscillator (SCS <1:0> = 00) pragma target PLLEN P1 -- PLL off pragma target WDT enabled -- watchdog on pragma target DEBUG disabled -- no debugging pragma target LVP disabled -- no Low Voltage Programming pragma target MCLR internal -- reset externally pragma target CLKOUTEN disabled -- no clk out -- These configuration bit settings are only a selection, sufficient for -- this program, but other programs may need more or different settings. -- -- IRFC field is bits 6-3 of OSCCON register -- -- OSCCON_IRCF = 0b1111 -- 16 MHz HF -- OSCCON_IRCF = 0b1110 -- 8 MHz or 32 MHz HF -- OSCCON_IRCF = 0b1101 -- 4 MHz HF -- OSCCON_IRCF = 0b1100 -- 2 MHz HF OSCCON_IRCF = 0b1011 -- 1 MHz HF -- OSCCON_IRCF = 0b1010 -- 500 kHz HF -- OSCCON_IRCF = 0b1001 -- 250 kHz HF -- OSCCON_IRCF = 0b1000 -- 125 kHz HF -- OSCCON_IRCF = 0b0111 -- 500 kHz MF (default upon Reset) -- OSCCON_IRCF = 0b0110 -- 250 kHz MF -- OSCCON_IRCF = 0b0101 -- 125 kHz MF -- OSCCON_IRCF = 0b0100 -- 62.5 kHz MF -- OSCCON_IRCF = 0b0011 -- 31.25 kHz HF -- OSCCON_IRCF = 0b0010 -- 31.25 kHz MF -- OSCCON_IRCF = 0b0001 -- 31.25 kHz LF -- OSCCON_IRCF = 0b0000 -- 31 kHz LF -- -- Watchdog Timer Period Select bits (bits 5-1 of WDTCON) -- -- WDTCON_WDTPS = 0b10010 -- 256 s nominal -- WDTCON_WDTPS = 0b10001 -- 128 s nominal -- WDTCON_WDTPS = 0b10000 -- 64 s nominal -- WDTCON_WDTPS = 0b01111 -- 32 s nominal -- WDTCON_WDTPS = 0b01110 -- 16 s nominal -- WDTCON_WDTPS = 0b01101 -- 8 s nominal -- WDTCON_WDTPS = 0b01100 -- 4 s nominal -- WDTCON_WDTPS = 0b01011 -- 2 s nominal WDTCON_WDTPS = 0b01010 -- 1 s nominal -- WDTCON_WDTPS = 0b01001 -- 512 ms nominal -- WDTCON_WDTPS = 0b01000 -- 256 ms nominal -- WDTCON_WDTPS = 0b00111 -- 128 ms nominal -- WDTCON_WDTPS = 0b00110 -- 64 ms nominal -- WDTCON_WDTPS = 0b00101 -- 32 ms nominal -- WDTCON_WDTPS = 0b00100 -- 16 ms nominal -- WDTCON_WDTPS = 0b00011 -- 8 ms nominal -- WDTCON_WDTPS = 0b00010 -- 4 ms nominal -- WDTCON_WDTPS = 0b00001 -- 2 ms nominal -- WDTCON_WDTPS = 0b00000 -- 1 ms nominal enable_digital_io() -- make all pins digital I/O -- Specify the pin to which the LED (with serial resistor) is connected: alias led is pin_A0 pin_A0_direction = output forever loop led = 0 _usec_delay(50_000) led = 1 assembler sleep -- sleep for a while nop -- pic12lf1822 continues here after WDT times out end assembler end loop
The code uses an inline-assembler code segment to put the processor to sleep during the time the LED is off to save power. Clock frequency and WDT sleep time are set by programming the appropriate processor registers.
[1] http://www.casadeyork.com/jalv2
[2] http://code.google.com/p/jallib/
