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Commit 53aa4f21 authored by Jake Read's avatar Jake Read
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add code from mkstepper for atsamd51 utils

parent 20935ef0
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README.md
View file @ 53aa4f21
......@@ -17,9 +17,9 @@ Eulagies aside, I am still motivated to do this. Brushless motors are the go-to
I'm not intending to put myself in league with these people - these links are here because they are motivated by (similar) things.
[ODrive](https://odriverobotics.com/shop)
[VESC](http://vedder.se/2015/01/vesc-open-source-esc/)
[Ben Katz](http://build-its-inprogress.blogspot.com/search/label/Motor%20Control)
[ODrive](https://odriverobotics.com/shop)
[VESC](http://vedder.se/2015/01/vesc-open-source-esc/)
[Ben Katz](http://build-its-inprogress.blogspot.com/search/label/Motor%20Control)
#### A few things to understand:
......
circuit/mkbldcdriver/eagle.epf
View file @ 53aa4f21
......@@ -8,7 +8,6 @@ Desktop="Desktop"
AutoSaveProject=1
UsedLibraryUrn="urn:adsk.eagle:library:217"
UsedLibraryUrn="urn:adsk.eagle:library:325"
UsedLibrary="D:/Dropbox (Personal)/CBA/doc/libraries/eagle/atsam.lbr"
UsedLibrary="D:/Dropbox (Personal)/CBA/doc/libraries/eagle/fab.lbr"
UsedLibrary="D:/Dropbox (Personal)/CBA/doc/libraries/eagle/motors.lbr"
UsedLibrary="D:/Dropbox (Personal)/CBA/doc/libraries/eagle/power.lbr"
......@@ -41,7 +40,7 @@ Loc="0 0 1919 1016"
State=1
Number=2
File="mkbldcdriver.sch"
View="-35.6514 3.39373 207.983 95.5307"
View="-127.358 -108.213 75.6708 -31.4319"
WireWidths=" 0.0762 0.1016 0.127 0.15 0.2 0.2032 0.254 0.3048 0.4064 0.508 0.6096 0.8128 1.016 1.27 2.54 0.1524"
PadDiameters=" 0.254 0.3048 0.4064 0.6096 0.8128 1.016 1.27 1.4224 1.6764 1.778 1.9304 2.1844 2.54 3.81 6.4516 0"
PadDrills=" 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.65 0.7 0.75 0.8 0.85 0.9 1 0.6"
......@@ -80,7 +79,7 @@ ArcDirection=0
AddLevel=2
PadsSameType=0
Layer=91
Views=" 1: -35.6514 3.39373 207.983 95.5307"
Views=" 1: -127.358 -108.213 75.6708 -31.4319"
Sheet="1"
[Win_2]
......@@ -89,7 +88,7 @@ Loc="0 0 1919 1016"
State=1
Number=1
File="mkbldcdriver.brd"
View="40.6143 32.1465 78.9523 33.3374"
View="10.5389 56.9239 37.1626 57.7509"
WireWidths=" 0.0762 0.1016 0.127 0.15 0.508 0.6096 0.8128 2.54 1.016 1.27 0.3048 0.254 0.2 0.4064 0.2032 0.1524"
PadDiameters=" 0.254 0.3048 0.4064 0.6096 0.8128 1.016 1.27 1.4224 1.6764 1.778 1.9304 2.1844 2.54 3.81 6.4516 0"
PadDrills=" 0.2 0.25 0.35 0.4 0.45 0.5 0.55 0.65 0.7 0.75 0.8 0.85 0.9 1 0.6 0.3"
......@@ -136,7 +135,7 @@ State=1
Number=0
[Desktop]
Screen="1920 1080"
Screen="3840 1080"
Window="Win_1"
Window="Win_2"
Window="Win_3"
embedded/mkbldcdriver-v03/mkbldcdriver-v03/Debug/Makefile
View file @ 53aa4f21
......@@ -40,7 +40,12 @@ SUBDIRS := \
C_SRCS += \
../Device_Startup/startup_samd51.c \
../Device_Startup/system_samd51.c \
../main.c
../main.c \
../pin.c \
../pwm_foc.c \
../ringbuffer.c \
../spiport.c \
../uartport.c
PREPROCESSING_SRCS +=
......@@ -52,22 +57,42 @@ ASM_SRCS +=
OBJS += \
Device_Startup/startup_samd51.o \
Device_Startup/system_samd51.o \
main.o
main.o \
pin.o \
pwm_foc.o \
ringbuffer.o \
spiport.o \
uartport.o
OBJS_AS_ARGS += \
Device_Startup/startup_samd51.o \
Device_Startup/system_samd51.o \
main.o
main.o \
pin.o \
pwm_foc.o \
ringbuffer.o \
spiport.o \
uartport.o
C_DEPS += \
Device_Startup/startup_samd51.d \
Device_Startup/system_samd51.d \
main.d
main.d \
pin.d \
pwm_foc.d \
ringbuffer.d \
spiport.d \
uartport.d
C_DEPS_AS_ARGS += \
Device_Startup/startup_samd51.d \
Device_Startup/system_samd51.d \
main.d
main.d \
pin.d \
pwm_foc.d \
ringbuffer.d \
spiport.d \
uartport.d
OUTPUT_FILE_PATH +=mkbldcdriver-v03.elf
......@@ -92,6 +117,16 @@ LINKER_SCRIPT_DEP+= \
Device_Startup/%.o: ../Device_Startup/%.c
@echo Building file: $<
@echo Invoking: ARM/GNU C Compiler : 6.3.1
......
embedded/mkbldcdriver-v03/mkbldcdriver-v03/Debug/makedep.mk
View file @ 53aa4f21
......@@ -8,3 +8,13 @@ Device_Startup\system_samd51.c
main.c
pin.c
pwm_foc.c
ringbuffer.c
spiport.c
uartport.c
embedded/mkbldcdriver-v03/mkbldcdriver-v03/hardware.h 0 → 100644
View file @ 53aa4f21
/*
* hardware.h
*
* Created: 2/17/2018 10:28:57 PM
* Author: Jake
*/
#ifndef HARDWARE_H_
#define HARDWARE_H_
#include "pin.h"
#include "ringbuffer.h"
#include "uartport.h"
#include "spiport.h"
pin_t stlb;
ringbuffer_t up1_rbrx;
ringbuffer_t up1_rbtx;
ringbuffer_t up2_rbrx;
ringbuffer_t up2_rbtx;
uartport_t up1;
uartport_t up2;
#endif /* HARDWARE_H_ */
\ No newline at end of file
embedded/mkbldcdriver-v03/mkbldcdriver-v03/main.c
View file @ 53aa4f21
......@@ -7,160 +7,81 @@
#include "sam.h"
#include "pwm_foc.h"
#include "pin.h"
#include "hardware.h"
#include <stdio.h>
// stlb is PA23
void pwmsetup(void){
/* TCC SETUP */
// from 49.6.2.1
// a few registers are protected - and can only be updated when
// TCCn.CTRLA.ENABLE = 0
// FCTRLA and FCTRLB, WEXCTRL, DRVCTRL, and EVCTRL
// (4) Configure Output Pin with PORT->Group[n].DIRSET.reg
// PA8 PA9 PA10 PA12, PB10 PB11
// 32.9.13
PORT->Group[0].DIRSET.reg |= (uint32_t)(1 << 8) | (uint32_t)(1 << 9) | (uint32_t)(1 << 10) | (uint32_t)(1 << 12);
PORT->Group[1].DIRSET.reg |= (uint32_t)(1 << 10) | (uint32_t)(1 << 11);
// 1 lo / hi
PORT->Group[0].PINCFG[10].bit.PMUXEN = 1;
PORT->Group[0].PMUX[10>>1].reg |= PORT_PMUX_PMUXE(0x5); // on peripheral F
PORT->Group[0].PINCFG[12].bit.PMUXEN = 1;
PORT->Group[0].PMUX[12>>1].reg |= PORT_PMUX_PMUXE(0x5);
// 2 lo / hi
PORT->Group[0].PINCFG[9].bit.PMUXEN = 1;
PORT->Group[0].PMUX[9>>1].reg |= PORT_PMUX_PMUXO(0x5); // on peripheral F
PORT->Group[1].PINCFG[11].bit.PMUXEN = 1;
PORT->Group[1].PMUX[11>>1].reg |= PORT_PMUX_PMUXO(0x5);
// 3 lo / hi
PORT->Group[0].PINCFG[8].bit.PMUXEN = 1;
PORT->Group[0].PMUX[8>>1].reg |= PORT_PMUX_PMUXE(0x5); // on peripheral F
PORT->Group[1].PINCFG[10].bit.PMUXEN = 1;
PORT->Group[1].PMUX[10>>1].reg |= PORT_PMUX_PMUXE(0x5);
// (1) enable the TCC Bus Clock - CLK_TCCn_APB
// https://www.eevblog.com/forum/microcontrollers/atmel-sam-d-tc-and-tcc-(no-asf)/
TCC0->CTRLA.bit.ENABLE = 0;
MCLK->APBBMASK.reg |= MCLK_APBBMASK_TCC0; // at 15.8.9
GCLK->GENCTRL[5].reg = GCLK_GENCTRL_SRC(GCLK_GENCTRL_SRC_DFLL) | GCLK_GENCTRL_GENEN;
while(GCLK->SYNCBUSY.reg & GCLK_SYNCBUSY_GENCTRL5);
GCLK->PCHCTRL[TCC0_GCLK_ID].reg = GCLK_PCHCTRL_CHEN | GCLK_PCHCTRL_GEN_GCLK5;
TCC0->CTRLA.reg |= TCC_CTRLA_PRESCALER_DIV8 | TCC_CTRLA_PRESCSYNC_PRESC |TCC_CTRLA_RESOLUTION(0);
// (2) Select Waveform Generation operation in the WAVE register WAVE.WAVEGEN
// we want dual slope pwm
TCC0->WAVE.reg = TCC_WAVE_WAVEGEN_DSBOTH; // 'dual slope both' - updates on both hi and lo of slope ?
// (3) We want OTMX - Output Matrix Channel Pin Routing Configuration - at 0x0
TCC0->WEXCTRL.reg = TCC_WEXCTRL_DTHS(1) | TCC_WEXCTRL_DTLS(1) |
TCC_WEXCTRL_DTIEN1 | TCC_WEXCTRL_DTIEN2 | TCC_WEXCTRL_DTIEN3 | TCC_WEXCTRL_DTIEN0 |
TCC_WEXCTRL_OTMX(0);
TCC0->PER.reg = TCC_PER_PER(256); // 18 bit
TCC0->COUNT.reg = 0;
TCC0->CC[0].reg = 0; // '3'
TCC0->CC[1].reg = 0; // '2'
TCC0->CC[2].reg = 0; // '1'
TCC0->CC[3].reg = 0;
// (4) Enable with CTRLA.ENABLE
TCC0->CTRLA.bit.ENABLE = 1;
while(TCC0->SYNCBUSY.bit.ENABLE);
}
void pwmupdate(uint32_t one, uint32_t two, uint32_t three){
TCC0->CC[0].reg = three; // '3'
TCC0->CC[1].reg = two; // '2'
TCC0->CC[2].reg = one; // '1'
}
int main(void)
{
/* Initialize the SAM system */
SystemInit();
PORT->Group[1].DIRSET.reg |= (uint32_t)(1 << 9);
PORT->Group[0].DIRSET.reg |= (uint32_t)(1 << 23);
SysTick_Config(5000000);
/* BEGIN SPI SETUP */
// PA04, SER0-0, SPI_MISO
// PA05, SER0-1, SPI_SCK
// PA06, SER0-2, SPI_CSN
// PA07, SER0-3, SPI_MOSI
PORT->Group[0].DIRCLR.reg |= (uint32_t)(1 << 4);
PORT->Group[0].DIRSET.reg |= (uint32_t)(1 << 5) | (uint32_t)(1 << 6) | (uint32_t)(1 << 7);
PORT->Group[0].PINCFG[4].bit.PMUXEN = 1;
PORT->Group[0].PMUX[4>>1].reg |= PORT_PMUX_PMUXE(0x3); // on peripheral D
PORT->Group[0].PINCFG[5].bit.PMUXEN = 1;
PORT->Group[0].PMUX[5>>1].reg |= PORT_PMUX_PMUXO(0x3); // on peripheral D
PORT->Group[0].PINCFG[6].bit.PMUXEN = 1;
PORT->Group[0].PMUX[6>>1].reg |= PORT_PMUX_PMUXE(0x3); // on peripheral D
PORT->Group[0].PINCFG[7].bit.PMUXEN = 1;
PORT->Group[0].PMUX[7>>1].reg |= PORT_PMUX_PMUXO(0x3); // on peripheral D
// setup clocks to sercom
MCLK->APBAMASK.reg |= MCLK_APBAMASK_SERCOM0; // at 15.8.9
GCLK->GENCTRL[6].reg = GCLK_GENCTRL_SRC(GCLK_GENCTRL_SRC_DFLL) | GCLK_GENCTRL_GENEN;
while(GCLK->SYNCBUSY.reg & GCLK_SYNCBUSY_GENCTRL6);
GCLK->PCHCTRL[SERCOM0_GCLK_ID_CORE].reg = GCLK_PCHCTRL_CHEN | GCLK_PCHCTRL_GEN_GCLK6;
// TCC0_GCLK_ID
// Some registers can't be written unless CTRL.ENABLE = 0:
// CTRLA, CTRLB, BAD and ADDR
// (1) set to master
SERCOM0->SPI.CTRLA.reg |= SERCOM_SPI_CTRLA_MODE(0x3); // 0x2 or 0x3, slave or master
// SERCOM0->SPI.CTRLA.reg |= SERCOM_SPI_CTRLA_CPHA | SERCOM_SPI_CTRLA_CPOL; // clock phase and polarity
// (2) set pin configurations
SERCOM0->SPI.CTRLA.reg |= SERCOM_SPI_CTRLA_DIPO(0x0) | SERCOM_SPI_CTRLA_DOPO(0x2); // pin selections, see 35.8.1 bits 21:20 and 17:16, pg. 910
// (3) set character size, data direction
//SERCOM0->SPI.CTRLA.reg |= SERCOM_SPI_CTRLA_DORD; // 0 MSB, 1 LSB
//SERCOM0->SPI.CTRLB.reg |= SERCOM_SPI_CTRLB_CHSIZE(0x0); // 8 bits character - 0x0, so no need to set
// LED
stlb = pin_new(&PORT->Group[0], 23);
pin_output(&stlb);
// interrupts
__enable_irq();
NVIC_EnableIRQ(SERCOM4_0_IRQn); //up1tx
NVIC_EnableIRQ(SERCOM4_2_IRQn); //up1rx
NVIC_EnableIRQ(SERCOM5_0_IRQn);
NVIC_EnableIRQ(SERCOM5_2_IRQn);
// Rinbuffers for UARTs
rb_init(&up1_rbrx);
rb_init(&up1_rbtx);
rb_init(&up1_rbrx);
rb_init(&up1_rbtx);
// UARTS
// UP1:
// SERCOM4 | RX: PB13 | TX: PB12
// UP2:
// SERCOM5 | RX: PB3 | TX: PB2
up1 = uart_new(SERCOM4, &PORT->Group[1], &up1_rbrx, &up1_rbtx, 12, 13, HARDWARE_IS_APBD, HARDWARE_ON_PERIPHERAL_C);
MCLK->APBDMASK.reg |= MCLK_APBDMASK_SERCOM4;
uart_init(&up1, 6, SERCOM4_GCLK_ID_CORE, 63018); // baud: 45402 for 921600, 63018 for 115200
up2 = uart_new(SERCOM5, &PORT->Group[1], &up2_rbrx, &up2_rbtx, 3, 2, HARDWARE_IS_APBD, HARDWARE_ON_PERIPHERAL_D);
MCLK->APBDMASK.reg |= MCLK_APBDMASK_SERCOM5;
uart_init(&up2, 7, SERCOM5_GCLK_ID_CORE, 63018);
// check all PWM lines
// pins for enable, fault, pwmmode, etc
// (4) setup baud rate
// f_baud = f_ref / (2 * (BAUD +1)) so BAUD = f_ref / (2 * f_baud) - 1
// integrate SPI, test AS5147, library
SERCOM0->SPI.BAUD.reg |= SERCOM_SPI_BAUD_BAUD(126);
SERCOM0->SPI.CTRLB.reg |= SERCOM_SPI_CTRLB_MSSEN | SERCOM_SPI_CTRLB_RXEN; // slave select hardware yes
// do closed loop sinucommutate, following old ATSAMS70 code
// do BLDC closed, open loop
SERCOM0->SPI.CTRLA.reg |= SERCOM_SPI_CTRLA_ENABLE;
pwmsetup_foc();
while (1)
{
while(!(SERCOM0->SPI.INTFLAG.bit.DRE));
SERCOM0->SPI.DATA.reg = SERCOM_SPI_DATA_DATA(80);
PORT->Group[1].OUTTGL.reg = (uint32_t)(1 << 9); // i-v, to check we made it thru setup
pwmupdate_foc(126,126,126);
}
}
void SysTick_Handler(void){
PORT->Group[0].OUTTGL.reg = (uint32_t)(1 << 23);
}
\ No newline at end of file
pin_toggle(&stlb);
uart_sendchar_buffered(&up1, 125);
}
void SERCOM4_0_Handler(void){
uart_txhandler(&up1);
}
void SERCOM4_2_Handler(void){
uart_rxhandler(&up1);
}
void SERCOM5_0_Handler(void){
uart_txhandler(&up2);
}
void SERCOM5_2_Handler(void){
uart_rxhandler(&up2);
}
embedded/mkbldcdriver-v03/mkbldcdriver-v03/mkbldcdriver-v03.cproj
View file @ 53aa4f21
......@@ -30,15 +30,15 @@
<EraseKey />
<AsfFrameworkConfig>
<framework-data xmlns="">
<options />
<configurations />
<files />
<documentation help="" />
<offline-documentation help="" />
<dependencies>
<content-extension eid="atmel.asf" uuidref="Atmel.ASF" version="3.36.2" />
</dependencies>
</framework-data>
<options />
<configurations />
<files />
<documentation help="" />
<offline-documentation help="" />
<dependencies>
<content-extension eid="atmel.asf" uuidref="Atmel.ASF" version="3.36.2" />
</dependencies>
</framework-data>
</AsfFrameworkConfig>
<avrtool>com.atmel.avrdbg.tool.atmelice</avrtool>
<avrtoolserialnumber>J41800087098</avrtoolserialnumber>
......@@ -165,9 +165,42 @@
<Compile Include="Device_Startup\system_samd51.c">
<SubType>compile</SubType>
</Compile>
<Compile Include="hardware.h">
<SubType>compile</SubType>
</Compile>
<Compile Include="main.c">
<SubType>compile</SubType>
</Compile>
<Compile Include="pin.c">
<SubType>compile</SubType>
</Compile>
<Compile Include="pin.h">
<SubType>compile</SubType>
</Compile>
<Compile Include="pwm_foc.c">
<SubType>compile</SubType>
</Compile>
<Compile Include="pwm_foc.h">
<SubType>compile</SubType>
</Compile>
<Compile Include="ringbuffer.c">
<SubType>compile</SubType>
</Compile>
<Compile Include="ringbuffer.h">
<SubType>compile</SubType>
</Compile>
<Compile Include="spiport.c">
<SubType>compile</SubType>
</Compile>
<Compile Include="spiport.h">
<SubType>compile</SubType>
</Compile>
<Compile Include="uartport.c">
<SubType>compile</SubType>
</Compile>
<Compile Include="uartport.h">
<SubType>compile</SubType>
</Compile>
</ItemGroup>
<ItemGroup>
<Folder Include="Device_Startup\" />
......
embedded/mkbldcdriver-v03/mkbldcdriver-v03/pin.c 0 → 100644
View file @ 53aa4f21
/*
* pin.c
*
* Created: 2/5/2018 11:21:37 PM
* Author: Jake
*/
#include "pin.h"
#include "sam.h"
pin_t pin_new(PortGroup *port, uint32_t pin_number){
pin_t pin;
pin.port = port;
pin.bm = (uint32_t)(1 << pin_number);
return pin;
}
void pin_output(pin_t *pin){
pin->port->DIRSET.reg = pin->bm;
pin->port->OUTCLR.reg = pin->bm;
}
void pin_input(pin_t *pin){
pin->port->DIRCLR.reg = pin->bm;
}
void pin_set(pin_t *pin){
pin->port->OUTSET.reg = pin->bm;
}
void pin_clear(pin_t *pin){
pin->port->OUTCLR.reg = pin->bm;
}
void pin_toggle(pin_t *pin){
pin->port->OUTTGL.reg = pin->bm;
}
int pin_read(pin_t *pin){
return pin->port->IN.reg & pin->bm;
}
\ No newline at end of file
embedded/mkbldcdriver-v03/mkbldcdriver-v03/pin.h 0 → 100644
View file @ 53aa4f21
/*
* pin.h
*
* Created: 2/5/2018 11:21:47 PM
* Author: Jake
*/
#ifndef PIN_H_
#define PIN_H_
#include "sam.h"
typedef struct {
PortGroup *port;
uint32_t bm; // bitmask
} pin_t;
pin_t pin_new(PortGroup *port, uint32_t pin);
void pin_output(pin_t *pin);
void pin_input(pin_t *pin);
void pin_set(pin_t *pin);
void pin_clear(pin_t *pin);
void pin_toggle(pin_t *pin);
int pin_read(pin_t *pin);
#endif /* PIN_H_ */
\ No newline at end of file
embedded/mkbldcdriver-v03/mkbldcdriver-v03/pwm_foc.c 0 → 100644
View file @ 53aa4f21
/*
* pwm.c
*
* Created: 2/17/2018 10:22:16 PM
* Author: Jake
*/
#include "pwm_foc.h"
void pwmsetup_foc(void){
/* TCC SETUP */
// from 49.6.2.1
// a few registers are protected - and can only be updated when
// TCCn.CTRLA.ENABLE = 0
// FCTRLA and FCTRLB, WEXCTRL, DRVCTRL, and EVCTRL
// (4) Configure Output Pin with PORT->Group[n].DIRSET.reg
// PA8 PA9 PA10 PA12, PB10 PB11
// 32.9.13
PORT->Group[0].DIRSET.reg |= (uint32_t)(1 << 8) | (uint32_t)(1 << 9) | (uint32_t)(1 << 10) | (uint32_t)(1 << 12);
PORT->Group[1].DIRSET.reg |= (uint32_t)(1 << 10) | (uint32_t)(1 << 11);
// 1 lo / hi
PORT->Group[0].PINCFG[10].bit.PMUXEN = 1;
PORT->Group[0].PMUX[10>>1].reg |= PORT_PMUX_PMUXE(0x5); // on peripheral F
PORT->Group[0].PINCFG[12].bit.PMUXEN = 1;
PORT->Group[0].PMUX[12>>1].reg |= PORT_PMUX_PMUXE(0x5);
// 2 lo / hi
PORT->Group[0].PINCFG[9].bit.PMUXEN = 1;
PORT->Group[0].PMUX[9>>1].reg |= PORT_PMUX_PMUXO(0x5); // on peripheral F
PORT->Group[1].PINCFG[11].bit.PMUXEN = 1;
PORT->Group[1].PMUX[11>>1].reg |= PORT_PMUX_PMUXO(0x5);
// 3 lo / hi
PORT->Group[0].PINCFG[8].bit.PMUXEN = 1;
PORT->Group[0].PMUX[8>>1].reg |= PORT_PMUX_PMUXE(0x5); // on peripheral F
PORT->Group[1].PINCFG[10].bit.PMUXEN = 1;
PORT->Group[1].PMUX[10>>1].reg |= PORT_PMUX_PMUXE(0x5);
// (1) enable the TCC Bus Clock - CLK_TCCn_APB
// https://www.eevblog.com/forum/microcontrollers/atmel-sam-d-tc-and-tcc-(no-asf)/
TCC0->CTRLA.bit.ENABLE = 0;
MCLK->APBBMASK.reg |= MCLK_APBBMASK_TCC0; // at 15.8.9
GCLK->GENCTRL[5].reg = GCLK_GENCTRL_SRC(GCLK_GENCTRL_SRC_DFLL) | GCLK_GENCTRL_GENEN;
while(GCLK->SYNCBUSY.reg & GCLK_SYNCBUSY_GENCTRL5);
GCLK->PCHCTRL[TCC0_GCLK_ID].reg = GCLK_PCHCTRL_CHEN | GCLK_PCHCTRL_GEN_GCLK5;
TCC0->CTRLA.reg |= TCC_CTRLA_PRESCALER_DIV8 | TCC_CTRLA_PRESCSYNC_PRESC |TCC_CTRLA_RESOLUTION(0);
// (2) Select Waveform Generation operation in the WAVE register WAVE.WAVEGEN
// we want dual slope pwm
TCC0->WAVE.reg = TCC_WAVE_WAVEGEN_DSBOTH; // 'dual slope both' - updates on both hi and lo of slope ?