External ADC Trigger for Teensy 3.x

ADC.h

@@ -180,6 +180,19 @@ extern "C"
         */
         __attribute__((error("Use adc->adcX->setAveraging instead"))) void setAveraging(uint8_t num, int8_t adc_num = -1);
 
+        //! Enable Hardwaretrigger
+        /** 
+         *  This enables analog to digital conversion by PDB or LBTR triggering
+        */
+        void setHardwareTrigger(int8_t adc_num = -1);
+
+        //! Enable SoftwareTrigger
+        /**
+        *   Enables analog to digital conversion by writing to SCA1 register
+        */
+        void setSoftwareTrigger(int8_t adc_num = -1);
+
+
         //! Enable interrupts
         /** An IRQ_ADCx Interrupt will be raised when the conversion is completed
         *  (including hardware averages and if the comparison (if any) is true).

ADC_Module.cpp

@@ -1591,10 +1591,16 @@ void ADC_Module::stopPDB()
         setSoftwareTrigger();
         return;
     }
+
+    // if (enablePDBisr) { NVIC_DISABLE_IRQ(IRQ_PDB); }
+
+    // https://forum.pjrc.com/threads/25532-ADC-library-update-now-with-support-for-Teensy-3-1/
+    // KurtE on 04-05-2018 12:06 PM
+    PDB0_CHnC1 = 0; // diasble ADC0 pre triggers
+
     PDB0_SC = 0;
     setSoftwareTrigger();
 
-    //NVIC_DISABLE_IRQ(IRQ_PDB);
 }
 
 //! Return the PDB's frequency
@@ -1719,4 +1725,143 @@ uint32_t ADC_Module::getQuadTimerFrequency()
 }
 
 #endif // Teensy 4
-#endif // ADC_USE_QUAD_TIMER
+#endif // ADC_USE_QUAD_TIMER
+
+
+//////////// EXT TRIG LPTMR ////////////////
+//// External Trigger through LPTMR hardware block
+//// https://github.com/manitou48/teensy3/blob/master/adclptmr.ino
+//
+// ADC trigger is on pin 13
+//
+// Example ISRs
+// ------------
+//volatile uint32_t aticks, lticks;
+//void adc0_isr() {
+//  aticks++;
+//  adcval = ADC0_RA;  // read and clear
+//}
+//
+//void lptmr_isr(void)      // not used
+//{
+//  LPTMR0_CSR |=  LPTMR_CSR_TCF;    // clear
+//  lticks++;
+//}
+// UU 2018-2020
+
+#ifdef ADC_USE_LPTMR
+void ADC_Module::startExtTrigLPTMR(bool enableLPTMRisr) {
+
+    if (!(SIM_SCGC5 & SIM_SCGC5_LPTIMER)) {         // setup LPTMR if not in use
+        SIM_SCGC5 |= SIM_SCGC5_LPTIMER;             // enable LPTMR
+        CORE_PIN13_CONFIG = PORT_PCR_MUX(3);        // pin 13 alt for LPTMR
+    }
+
+    LPTMR0_CSR  = 0;                               // Disable (necessary to make changes to LPTMR)
+    LPTMR0_PSR  = LPTMR_PSR_PBYP;                  // Bypass prescaler/glitch filter
+    LPTMR0_CMR  = 1;                               // Counts til interrupt occurs, rate = freq/(CMR+1)
+                                                   // If CMR = 0 hardware trigger remains asserted until LPTMR disabled
+    if (enableLPTMRisr) {
+    LPTMR0_CSR  = LPTMR_CSR_TIE |                  // Interrupt Enable
+                  LPTMR_CSR_TPS(2) |               // Pin: 0=CMP0, 1=xtal, 2=pin13
+                //LPTMR_CSR_TFC |                  // Free-Running Counter
+                  LPTMR_CSR_TMS;                   // Mode Select, 0=timer, 1=counter
+    } else {
+    LPTMR0_CSR  = LPTMR_CSR_TPS(2) |               // Pin: 0=CMP0, 1=xtal, 2=pin13
+                //LPTMR_CSR_TFC |                  // Free-Running Counter
+                  LPTMR_CSR_TMS;                   // Mode Select, 0=timer, 1=counter
+    }
+    LPTMR0_CSR |=   LPTMR_CSR_TEN;                 // Enable
+
+    // Set ADCn to trigger from the LPTMR
+    SIM_SOPT7   = (ADC_num? SIM_SOPT7_ADC1ALTTRGEN   : SIM_SOPT7_ADC0ALTTRGEN)  |   // Enable ADCn alternate trigger
+                  (ADC_num? SIM_SOPT7_ADC1TRGSEL(14) : SIM_SOPT7_ADC0TRGSEL(14));   // Trigger ADCn by LPTMR0
+    setHardwareTrigger();                          // trigger ADC with hardware
+
+    if (enableLPTMRisr) { NVIC_ENABLE_IRQ(IRQ_LPTMR); }
+}
+
+void ADC_Module::stopExtTrigLPTMR(bool enableLPTMRisr) {
+
+    if (!(SIM_SCGC5 & SIM_SCGC5_LPTIMER)) {        // if LPTMR wasn't enabled, return
+        return;
+    }
+
+    if (enableLPTMRisr) { NVIC_DISABLE_IRQ(IRQ_LPTMR); }
+
+    LPTMR0_CSR = 0;                                // Disable
+    setSoftwareTrigger();
+}
+
+#endif
+
+//////////// EXT TRIG PDB ////////////////
+//// External Trigger though PDB hardware block
+// https://forum.pjrc.com/threads/24492-Using-the-PDB-on-Teensy-3?p=128046&viewfull=1#post128046
+// manitou 12-20-2016 04:03 PM
+//
+// ADC trigger is on pin 11
+//
+// Example ISRs
+// ------------
+//
+//volatile uint32_t pdbticks;
+//
+//void pdb_isr() {
+//  PDB0_SC = (PDB_SC_TRGSEL(00) | PDB_SC_PDBEN | PDB_SC_PDBIE ) | PDB_SC_LDOK; // (also clears interrupt flag)
+//  pdbticks++;
+//}
+// UU 2018-2020
+
+#ifdef ADC_USE_PDB
+
+// frequency in Hz
+void ADC_Module::startExtTrigPDB(bool enablePDBisr) {
+    if (!(SIM_SCGC6 & SIM_SCGC6_PDB)) {        // Setup PDB
+         SIM_SCGC6 |= SIM_SCGC6_PDB;           // Enable the PDB clock
+        CORE_PIN11_CONFIG = PORT_PCR_MUX(3);   // pin 11 alt for PDB
+    }
+
+    // remove later
+    // PDB pre trigger selection
+    //constexpr uint32_t PDB_CHnC1_TOS_1 = 0x0100;
+    //constexpr uint32_t PDB_CHnC1_EN_1 = 0x01;
+    //PDB0_CHnC1 = PDB_CHnC1_TOS_1 | PDB_CHnC1_EN_1; // enable pretrigger 0 (SC1A)
+    // remove later
+
+    PDB0_IDLY = 0; // the pdb interrupt delay CNT+0
+    //           external trigger  | PDB enable   | interrupt enable   
+    if (enablePDBisr) { 
+      // might also need: continuous mode | load immediately
+      //                    | PDB_SC_CONT | PDB_SC_LDMOD(0);
+      PDB0_SC = (PDB_SC_TRGSEL(00) | PDB_SC_PDBEN | PDB_SC_PDBIE);
+    } else {
+      PDB0_SC = (PDB_SC_TRGSEL(00) | PDB_SC_PDBEN);
+    }
+    // loads the registers MOD, IDLY, CHnDLYm, DACINTx,and POyDLY after PDBEN is set
+    PDB0_SC |= PDB_SC_LDOK;
+
+    // Set ADCn to trigger from the PDB
+    SIM_SOPT7   = (ADC_num? SIM_SOPT7_ADC1ALTTRGEN  : SIM_SOPT7_ADC0ALTTRGEN)  |   // Enable ADCn alternate trigger
+                  (ADC_num? SIM_SOPT7_ADC1TRGSEL(0) : SIM_SOPT7_ADC0TRGSEL(0));    // Trigger ADCn PDB0_EXTRG
+    // trigger ADC with hardware
+    setHardwareTrigger();
+
+    if (enablePDBisr) { NVIC_ENABLE_IRQ(IRQ_PDB); }
+}
+
+void ADC_Module::stopExtTrigPDB(bool enablePDBisr) {
+    if (!(SIM_SCGC6 & SIM_SCGC6_PDB)) {         // if PDB wasn't on, return
+        setSoftwareTrigger();
+        return;
+    }
+
+    if (enablePDBisr) {NVIC_DISABLE_IRQ(IRQ_PDB);}
+
+    PDB0_CHnC1 = 0; // diasble ADC0 pre triggers
+    PDB0_SC = 0;    // reset configuration register
+
+    setSoftwareTrigger();
+}
+
+#endif

ADC_Module.h

@@ -586,6 +586,32 @@ class ADC_Module
     uint32_t getQuadTimerFrequency();
 #endif
 
+    //////////// LPTMR  Ext Trig////////////////
+#ifdef ADC_USE_LPTMR
+    //! Start external pin 13 LPTMR triggering the ADC
+    /** Call startSingleRead or startSingleDifferential on the pin that you want to measure after calling this function.
+    *   See the example adc_lptmr.ino.
+    */
+    void startExtTrigLPTMR(bool enableLPTMRisr);
+    void startExtTrigLPTMR() { startExtTrigLPTMR(false); }
+    //! Stop the LPTMR
+    void stopExtTrigLPTMR(bool enableLPTMRisr);
+    void stopExtTrigLPTMR() { stopExtTrigLPTMR(false); }
+#endif
+
+    //////////// PDB Ext Trig ////////////////
+#ifdef ADC_USE_PDB
+    //! Start external pin 11 PDB triggering the ADC
+    /** Call startSingleRead or startSingleDifferential on the pin that you want to measure after calling this function.
+    *   See the example adc_ext_pdb.ino.
+    */
+    void startExtTrigPDB(bool enablePDBisr);
+    void startExtTrigPDB() { startExtTrigPDB(false); }
+    //! Stop the LPTMR
+    void stopExtTrigPDB(bool enablePDBisr);
+    void stopExtTrigPDB() { stopExtTrigPDB(false); }
+#endif
+
     //////// OTHER STUFF ///////////
 
     //! Store the config of the adc

README.md

@@ -9,6 +9,10 @@ If you download the library from here, also install the latest Teensyduino versi
 This thread in the Teensy forum also has information:
 http://forum.pjrc.com/threads/25532-ADC-library-update-now-with-support-for-Teensy-3-1
 
+# Updates
+
+This library was modified to include external trigger support (does not support Teensy 4.x)
+
 # License
 
 Teensy 4.x, 3.x, LC ADC library

examples/adc_external_clock/adc_lptr_extTrigger/adc_lptr_extTrigger.ino

@@ -0,0 +1,91 @@
+// Teensy external ADC clock example 
+//
+// This program uses pin23 as "external" clock for ADC conversion.
+// It increases the clock and reports if adc conversion were missed.
+// You will need to create a connection between pin 23 and pin 13.
+//
+// We are using the LPTMR hardware module:
+// adclptmr uses LPTMR0 counter (pin 13) to clock ADC A0
+
+// ------------------------------------
+// Teensy 3.2
+// ------------------------------------
+//ADCr rates
+// Averaging 0 ------------------------
+// 16 bit 735kS/s, VERY_HIGH, VERY_HIGH
+// 12 bit 835kS/s, VERY_HIGH, VERY_HIGH
+//  8 bit 975kS/s, VERY_HIGH, VERY_HIGH
+// 16 bit 365kS/s, HIGH16, HIGH
+// 16 bit 365kS/s, HIGH, HIGH
+// 12 bit 430kS/s, HIGH, HIGH
+//  8 bit 480kS/s, HIGH, HIGH
+// Averaging 4 ------------------------
+// 16 bit 205kS/s, VERY_HIGH, VERY_HIGH
+// 12 bit 255kS/s, VERY_HIGH, VERY_HIGH
+// 8  bit 290kS/s, VERY_HIGH, VERY_HIGH
+// ------------------------------------
+
+#include "ADC.h"
+ADC *adc = new ADC();
+
+#define PIN_ADC 5                                                     // A0, Pin 14
+#define PRINTREGISTER(x) Serial.print(#x" 0x"); Serial.println(x,HEX)
+
+volatile uint32_t lptmrticks, adcticks, adcval;
+
+void lptmr_isr(void)
+{
+  LPTMR0_CSR |=  LPTMR_CSR_TCF; // clear
+  lptmrticks++;
+}
+
+void adc0_isr() {
+  adcticks++;
+  adcval = adc->adc0->readSingle();
+}
+
+void adc_init() {
+  adc->adc0->disablePGA();        
+  adc->adc0->setReference(ADC_REFERENCE::REF_3V3);
+  adc->adc0->setAveraging(0); 
+  adc->adc0->setResolution(8); 
+  adc->adc0->disableCompare();
+  adc->adc0->setConversionSpeed(ADC_CONVERSION_SPEED::VERY_HIGH_SPEED);
+  adc->adc0->setSamplingSpeed(ADC_SAMPLING_SPEED::VERY_HIGH_SPEED);      
+}
+
+void setup() {
+  Serial.begin(9600);
+  while (!Serial);
+  pinMode(PIN_ADC, INPUT);
+  pinMode(23, OUTPUT);
+  delay(1000);
+  adc_init();
+}
+
+float    delta, expected;
+uint32_t t, cnta=0, cntl=0;
+elapsedMicros sinceStart_micros;
+
+void loop() {
+  for (long Fadc = 500000; Fadc < 2000000; Fadc = Fadc+5000) {
+    adc->adc0->startExtTrigLPTMR(true);              // enable external LPTMR trigger and its interrupt
+    adc->adc0->startSingleRead(PIN_ADC);             // call this to setup everything before the pdb starts, differential is also possible
+    adc->adc0->enableInterrupts(adc0_isr);
+    analogWriteResolution(4);                        // Setup trigger clock
+    analogWriteFrequency(23,long(Fadc*2));           // Create clock on pin13
+    analogWrite(23, 8);                              // 50% dutycycle clock
+    sinceStart_micros = 0; 
+    adcticks = 0;
+    lptmrticks = 0;
+    delay(1000);
+    t=sinceStart_micros, cnta=adcticks; cntl= lptmrticks;
+    adc->adc0->stopExtTrigLPTMR(true);              // stop external LPTMR trigger and its interrupt
+    expected = t*1.e-6*Fadc;
+    delta = (cnta-expected)*1000000.0/t;
+    Serial.printf("Freq: %d", Fadc); 
+    Serial.printf(" ADC %d", cnta); 
+    Serial.printf(" LPT %d", cntl); 
+    Serial.printf(" off by %+.3f Hz\n", delta);
+  }
+}