ARM: implement analog-arm.c.

Very simple, because the LPC1114 features a hardware scan mode,
which automatically scans a given set of pins in freerunning mode
and stores all the values separately. No need for an interrupt!

Not yet done: configure not PIO1_0 and PIO1_1, but the pins
actually defined in the board file.

For testing, add this to ifclock(clock_flag_1s) in clock.c:
  uint8_t i;

  for (i = 0; i <= 7; i++) {
    sersendf_P(PSTR("%lu "), analog_read(i));
  }
  serial_writechar('\n');

This should print all 8 ADC values repeatedly. Only two pins are
actually set up, these values should change depending on the
thermistor temperature. More precisely: depending on the voltage
on the pin.

Makefile-ARM

@@ -100,8 +100,9 @@ TARGET = $(PROGRAM).hex
 SOURCES  = mendel.c cpu.c serial.c sermsg.c sersendf.c delay.c
 SOURCES += gcode_parse.c gcode_process.c pinio.c timer.c clock.c
 SOURCES += dda_queue.c dda_maths.c dda_kinematics.c dda.c dda_lookahead.c
+SOURCES += analog.c
 # Sources left:
-# analog.c home.c crc.c intercom.c debug.c spi.c usb_serial.c
+# home.c crc.c intercom.c debug.c spi.c usb_serial.c
 # graycode.c pff.c temp.c watchdog.c heater.c pff_diskio.c
 
 ifeq ($(MCU), lpc1114)

analog-arm.c

@@ -0,0 +1,80 @@
+
+/** \file
+  \brief Analog subsystem, ARM specific part.
+
+  Nice feature of the LPC11xx is, it features a hardware scan mode, which scans
+  a given set of ADC pins over and over again, without need for an interrupt
+  to switch between channels. Our code becomes pretty simple: set this
+  mechanism up at init time and be done for the time being.
+
+  Unlike ATmegas, LPC1114 features no analog voltage reference selector, it
+  always compares against Vdd. This is the equivalent of REFERENCE_AVCC on AVR.
+*/
+
+#if defined TEACUP_C_INCLUDE && defined __ARMEL__
+
+#include "cmsis-lpc11xx.h"
+#include "arduino.h"
+#include "temp.h"
+
+
+/** Inititalise the analog subsystem.
+
+  Initialise the ADC and start hardware scan loop for all used sensors.
+
+  LPC111x User Manual recommends an ADC clock of 4.5 MHz ("typically"), still
+  we reduce this to 1 MHz, because we're not nearly as much in a hurry. A
+  conversion needs 11 ADC clocks per channel, so we still get many thousand
+  conversions/second; we need just 100/s.
+*/
+void analog_init() {
+
+  if (NUM_TEMP_SENSORS) {                       // At least one channel in use.
+
+    LPC_SYSCON->PDRUNCFG &= ~(1 << 4);            // Turn on ADC clock.
+    LPC_SYSCON->SYSAHBCLKCTRL |= (1 << 13);       // Turn on ADC power.
+
+    /**
+      Register name mapping from LPC111x User Manual to CMSIS headers:
+
+        chap. 25.5     cmsis-lpc11xx.h   description
+
+        AD0CR          LPC_ADC->CR       A/D control register.
+        AD0GDR         LPC_ADC->GDR      A/D global data register.
+        AD0INTEN       LPC_ADC->INTEN    A/D interrupt enable register.
+        AD0DRn         LPC_ADC->DR[n]    A/D channel n data register.
+        AD0STAT        LPC_ADC->STAT     A/D status register.
+    */
+    // TODO: enable only the channels we use.
+    LPC_ADC->CR = (0xFF << 0)                     // All pins on (for now).
+                | ((F_CPU / 1000000) << 8)        // 1 MHz ADC clock.
+                | (1 << 16)                       // Hardware scan mode.
+                | (0x0 << 17)                     // Maximum accuracy.
+                | (0x0 << 24);                    // Clear START.
+
+    LPC_ADC->INTEN = 0;                           // No interrupt generation.
+
+    // TODO: set up the channels configured, not two arbitrary ones.
+    LPC_IOCON->PIO1_0_CMSIS = (0x2 << 0)          // Function AD1.
+                            | (0 << 3)            // Pullup inactive.
+                            | (0 << 7);           // Analog input mode.
+    LPC_IOCON->PIO1_1_CMSIS = (0x2 << 0)          // Function AD2.
+                            | (0 << 3)            // Pullup inactive.
+                            | (0 << 7);           // Analog input mode.
+  }
+}
+
+/** Read analog value.
+
+  \param channel Channel to be read.
+
+  \return Analog reading, 10-bit right aligned.
+
+  Hardware scan mode nicely saves all the converted values separately, so
+  there's no need to hold them in a copy.
+*/
+uint16_t analog_read(uint8_t index) {
+  return (LPC_ADC->DR[index] & 0xFFC0) >> 6;
+}
+
+#endif /* defined TEACUP_C_INCLUDE && defined __ARMEL__ */

analog.c

@@ -7,7 +7,7 @@
 
 #define TEACUP_C_INCLUDE
 #include "analog-avr.c"
-//#include "analog-arm.c"
+#include "analog-arm.c"
 #undef TEACUP_C_INCLUDE
 
 // No common code so far.

mendel.c

@@ -39,8 +39,8 @@
 #include	"watchdog.h"
 #include	"debug.h"
 #include	"heater.h"
-#include	"analog.h"
 #endif /* __ARMEL_NOTYET__ */
+#include	"analog.h"
 #include	"pinio.h"
 #include	"clock.h"
 #ifndef __ARMEL_NOTYET__
@@ -105,11 +105,11 @@ void init(void) {
 	// set up dda
 	dda_init();
 
-  #ifndef __ARMEL_NOTYET__
 	// start up analog read interrupt loop,
 	// if any of the temp sensors in your config.h use analog interface
 	analog_init();
 
+  #ifndef __ARMEL_NOTYET__
 	// set up temperature inputs
 	temp_init();