LPC54628: Update the ADC clock divider based on the input clock source

1. Problems were seen on the LPC54628 as the ADC clock source was too
   high
2. Moved the pin configuration to set Analog mode to the end of the
   function

Signed-off-by: Mahesh Mahadevan <[email protected]>

Author: mmahadevan108

targets/TARGET_NXP/TARGET_MCUXpresso_MCUS/TARGET_LPC/analogin_api.c

@@ -30,9 +30,13 @@ static ADC_Type *const adc_addrs[] = ADC_BASE_PTRS;
 extern void ADC_ClockPower_Configuration(void);
 
 #define MAX_FADC 6000000
+#define MAX_ADC_CLOCK 80000000
 
 void analogin_init(analogin_t *obj, PinName pin)
 {
+    uint32_t clkval;
+    uint32_t clkdiv = 1;
+
     obj->adc = (ADCName)pinmap_peripheral(pin, PinMap_ADC);
     MBED_ASSERT(obj->adc != (ADCName)NC);
 
@@ -42,23 +46,29 @@ void analogin_init(analogin_t *obj, PinName pin)
     uint32_t pin_number = pin & 0x1F;
     uint8_t port_number = pin / 32;
 
-    /* Clear the DIGIMODE bit */
-    reg = IOCON->PIO[port_number][pin_number] & ~IOCON_PIO_DIGIMODE_MASK;
-    IOCON->PIO[port_number][pin_number] = reg;
-
     ADC_ClockPower_Configuration();
 
+    /* Ensure the ADC clock derived from the system clock is less than 80MHz */
+    clkval = CLOCK_GetFreq(kCLOCK_CoreSysClk);
+    while ((clkval / clkdiv) > MAX_ADC_CLOCK) {
+        clkdiv++;
+    }
+
     /* Calibration after power up. */
     if (!(ADC_DoSelfCalibration(adc_addrs[instance]))) {
         /* Calibration failed */
         return;
     }
 
     ADC_GetDefaultConfig(&adc_config);
-    adc_config.clockDividerNumber = 1;
+    adc_config.clockDividerNumber = clkdiv;
 
     ADC_Init(adc_addrs[instance], &adc_config);
     pinmap_pinout(pin, PinMap_ADC);
+
+    /* Clear the DIGIMODE bit */
+    reg = IOCON->PIO[port_number][pin_number] & ~IOCON_PIO_DIGIMODE_MASK;
+    IOCON->PIO[port_number][pin_number] = reg;
 }
 
 uint16_t analogin_read_u16(analogin_t *obj)
@@ -70,7 +80,7 @@ uint16_t analogin_read_u16(analogin_t *obj)
 
     adcConvSeqConfigStruct.channelMask = (1U << channel);
     adcConvSeqConfigStruct.triggerMask = 0U;
-    adcConvSeqConfigStruct.triggerPolarity = kADC_TriggerPolarityNegativeEdge;
+    adcConvSeqConfigStruct.triggerPolarity = kADC_TriggerPolarityPositiveEdge;
     adcConvSeqConfigStruct.enableSingleStep = false;
     adcConvSeqConfigStruct.enableSyncBypass = false;
     adcConvSeqConfigStruct.interruptMode = kADC_InterruptForEachSequence;