Add PWM mode to GPIO.

Period is 3000, this makes the pwm frequency about 330 Hz and the
theoretical resolution about 16 bits.

The effective resolution is probably about 14-15 bits, but the duty
cycle can be configured to the whole 16 bit range:
    0 (off),
    1-65534 and
    65535 (on).
Values between 55000 and 65535 probably all mean "on" and values below
16 are probably all "off". Your mileage may vary.

Author: Erik Slagter

Makefile

@@ -7,7 +7,7 @@ CINC			= -I$(SDKROOT)/lx106-hal/include -I$(SDKROOT)/xtensa-lx106-elf/xtensa-lx1
 LDFLAGS			= -nostdlib -Wl,--no-check-sections -u call_user_start -Wl,-static
 LDSCRIPT		= -T$(SDKLD)/eagle.app.v6.ld
 LDSDK			= -L$(SDKROOT)/sdk/lib
-LDLIBS			= -lc -lgcc -lhal -lpp -lphy -lnet80211 -llwip -lwpa -lmain
+LDLIBS			= -lc -lgcc -lhal -lpp -lphy -lnet80211 -llwip -lwpa -lmain -lpwm
 
 OBJS			= application.o config.o gpios.o queue.o stats.o uart.o user_main.o util.o wlan.o
 HEADERS			= esp-uart-register.h \

README.md

@@ -63,24 +63,29 @@ These are the currently implemented commands on port 24:
 		gd	gpio-dump		none			dump gpio configuration and current status
 		gg	gpio-get		gpio			for example gpio2; reads the the gpio as input
 											(if set to mode input)
-		gm	gpio-mode		varies			none: dump all gpio's
+		gm	gpio-mode		VARIES			none: dump all gpio's
 											<gpio> disable: disable the gpio
 											<gpio> input: set gpio to input
-											<gpio> output <startup>: set gpio to output,
-												set <startup> to 0 or 1 to define the startup
-												value (after boot)
+											<gpio> output <startup state>: set gpio to output,
+												set <startup state> to 0 or 1 to configure the state
+												of the output directly after boot.
 											<gpio> bounce <direction> <delay> <repeat> <autotrigger>
 												<direction> = up or down, specifying whether to bounce
 													from "off" or "on"
 												<delay> = value in milliseconds between triggered state
 													and resuming normal gpio state
 												<repeat> = 0 or 1, 0 means once, 1 means repeating
 													until stopped manually
-												<autotrigger> = 0 or 1, 0 means leave the gpio alone
-													after boot, need to trigger manually (using gpio-set),
-													1 means trigger automatically after boot
+												<autotrigger> = 0 or 1,
+													0 means leave the gpio alone after boot, need to
+														trigger manually (using gpio-set),
+													1 means trigger automatically after boot.
+											<gpio> pwm [<startup duty cycle>]
+												<startup duty cycle> is the duty cycle after boot,
+												default 0 for off.
 		gs	gpio-set		<gpio> (value)	set the gpio if it's set as output, if set
-											as bounce, trigger a bounce
+											as bounce, trigger a bounce, if it's set as pwm, set
+											the duty cycle (startup value is taken if it's missing).
 		?	help			none			shows list of commands
 		pd	print-debug		0 or 1			0 = enable, 1 = enable
 											toggle printing of debug info during