mimxrt/main: Extend the information returned by help().

ports/mimxrt/main.c

@@ -131,8 +131,23 @@ const char mimxrt_help_text[] =
     "  machine.Pin(pin, m, [p]) -- get a pin and configure it for IO mode m, pull mode p\n"
     "    methods: init(..), value([v]), high(), low())\n"
     "\n"
-    "Pin IO modes are: Pin.IN, Pin.OUT, Pin.OPEN_DRAIN\n"
-    "Pin pull modes are: Pin.PULL_UP, Pin.PULL_UP_47K, Pin.PULL_UP_22K, Pin.PULL_DOWN, Pin.PULL_HOLD\n"
+    "    Pins are numbered board specific, either 0-n, or 'D0'-'Dn', or 'A0' - 'An',\n"
+    "    according to the boards's pinout sheet.\n"
+    "    Pin IO modes are: Pin.IN, Pin.OUT, Pin.OPEN_DRAIN\n"
+    "    Pin pull modes are: Pin.PULL_UP, Pin.PULL_UP_47K, Pin.PULL_UP_22K, Pin.PULL_DOWN, Pin.PULL_HOLD\n"
+    "  machine.ADC(pin) -- make an analog object from a pin\n"
+    "    methods: read_u16()\n"
+    "  machine.UART(id, baudrate=115200) -- create an UART object (id=1 - 8)\n"
+    "    methods: init(), write(buf), any()\n"
+    "             buf=read(n), readinto(buf), buf=readline()\n"
+    "    The RX and TX pins are fixed and board-specific.\n"
+    "  machine.SoftI2C() -- create an Soft I2C object\n"
+    "    methods: readfrom(addr, buf, stop=True), writeto(addr, buf, stop=True)\n"
+    "             readfrom_mem(addr, memaddr, arg), writeto_mem(addr, memaddr, arg)\n"
+    "  machine.SoftSPI(baudrate=1000000) -- create an SPI object ()\n"
+    "    methods: read(nbytes, write=0x00), write(buf), write_readinto(wr_buf, rd_buf)\n"
+    "  machine.Timer(id, freq, callback) -- create a hardware timer object (id=0,1,2)\n"
+    "    eg: machine.Timer(freq=1, callback=lambda t:print(t))\n"
     "\n"
     "Useful control commands:\n"
     "  CTRL-C -- interrupt a running program\n"