dsPIC33CH Curiosity Timers

Here we will show various types of dsPIC33CH Timers and their usage on Curiosity board.

Hardware Requirements:

• dsPIC33CH Curiosity Development Board
• Micro USB cable (there is no one included with board!)
• ensure that you downloaded data-sheet from:
  • https://ww1.microchip.com/downloads/en/DeviceDoc/DS50002801%20-%20dsPIC33CH%20Curiosity%20Development%20Board%20Users%20Guide.pdf
• Notice dsPIC type from data-sheet:
  • dsPIC33CH512MP508

Software Requirements:

• MPLAB X IDE v6.10 + Updates

  WARNING! You need to install latest updates when running this verson of MPLAB for the first time. Otherwise PicKit programmer on board (PKOB) will not work!

• DFP: dsPIC33CH-MP_DFP v1.7.194
• XC16 v2.10
• recommended: Download official Curiosity board example:
  • download: https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ProductDocuments/SoftwareLibraries/Firmware/dspic33ch512_curiosity_demo.zip
  • page: https://www.microchip.com/en-us/development-tool/DM330028-2

For Demos with UART you additionally need:

• 2nd Micro USB cable (not included with Curiosity)
• for Windows < 10 download driver from
  • https://www.microchip.com/en-us/product/MCP2221A
  • for example: https://ww1.microchip.com/downloads/en/DeviceDoc/MCP2221_Windows_Driver_2021-02-22.zip

Project

In this project we will incrementally test various kinds of Timers and their use cases.

There are Debug messages on UART. You have to use Putty on Windows and configure these transfer parameters:

• Baud rate: 115200 (I had no luck with theoretical maximum 460800)
• 8-data bits
• Odd parity - non-standard!!!
• No flow control

Implemented Functions:

• using only Master Core running at maximum cycle frequency f_cy = 90 MHz (90 MIPS)
• if any Trap occurs both RED LED1 and RED LED2 will be lit forever.
• main thread: rotating RGB LED every 1s using __delay_ms(1000): Red -> Green -> Blue -> All off
• TMR1 callback at 1 kHz rate, toggle RB11 at this rate (frequency 500 Hz) (verified with Digilent Analog Discovery 2 scope - got exactly 500.00 Hz)
• 32-bit Timer from SCPP1 module Flipping RED LED1 at 10 Hz rate => blinking frequency 5 Hz. Interrupt rate is simply f_cy / PERIOD = 90'000'000 Hz / 9'000'000 = = 10 Hz So PERIOD registers (CCP1PRH:CP1PRL) are set to 9'000'000 => 0x89'5440 - as can be verified generated code at TimersMaster.X\mcc_generated_files\sccp1_tmr.c
  • RED LED1 output is on RE0 pin - frequency verified on scope.
  • it is recommended application of 32-bit timers - for very slow interrupt generation
• RB12 PWM output at 100 kHz on RB12 using SCCP2 module. It is done in hardware entirely without software assistance - which is intentional. Generally for higher frequencies one should try to utilize hardware as much as possible.
  • NOTE: Actual registers should have VALUE-1, because both transition to high and reset changes after maximum value is reached, counting from 0 - so it is like command for(i=0;i<=MAX_VALUE;i++){...}. For details please see
    • Figure 64-18: Timing for Dual Edge Compare (Timer Period = CCPxRB)
    • on DS33035A-page 64-31
• RC2 SCCP3 - PWM Output at 100 kHz but with just 1 micro-second pulse synchronized to SCCP2. The start of SCCP3 module is synchronized to SCCP2 rollover using Sync Input SCCP2 so pulses should be always properly aligned (I hope!).

Both SCCP2 and SCCP3 aligned outputs shown on picture below:

Again, it is done in hardware entirely - no software assistance needed.

TODO: Verify if SCCP2 pulses are really aligned (using very low frequency).

Example UART output:

MASTER: startup main.c:94 main(): v1:02 Aug 19 2023
  i=0 Uptime=0.0 [sec] Total=4 [ms] Delta=4 [ms]
  i=1 Uptime=4.0 [sec] Total=4020 [ms] Delta=4016 [ms]
  i=2 Uptime=8.0 [sec] Total=8036 [ms] Delta=4016 [ms]
  ...

Ideal output should be Delta=4000 [ms] however we don't use any kind of overhead compensation (for toggling LEDs, printf(3), UART synchronous write, etc...). So measured overhead around 1.4 micro-seconds is fine for this example.

Curiosity board Notes

Please note that when you create new project you need to select:

• Family: 16-bit DSCs (dsPIC33)
• Device: dsPIC33CH512MP508 for Master Core. If you will create also Slave project you have to select same CPU with S1 (Slave) suffix
• Tool: Starter Kits (PKOB)-SN:BURxxx (you need to have your Curiosity board

Here is brief overview of I/O peripherals on Curiosity board - excluding DC/DC converter parts:

Peripheral	dsPIC33CH pin and/or port
S1 push-button	RE7
S2 push-button	RE8
S3 push-button	RE9
S4 push-button	/MCLR (reset)
R/G/B LED	RD5/RD7/RB14
LED1 red	RE0
LED2 red	RE1
10kOhm pot	RA0

Master core supports up to f_cy = 90 MHz (MIPS). In MCC Tool I have to configure clock this way:

• clock Type: Primary (there is accurate 8 MHz clock base on Curiosity board)
• enable PLL and set it to:
• Prescaler: 1:1 -> 8 Mhz
• Feedback: 1:180 -> 1440 MHz
• Postscale1: 1:4 -> 360 MHz
• Postscaler2: 1:1 -> 360 MHz
• output oscillator frequency: f_osc = 180 MHz
• final instruction cycle frequency: f_cy = 90 MHz = 90 MIPS

Also set Auxiliary Clock to Primary.

ICD: Ensure that PGC2 and PGD2 are selected (valid for PKOB programmer debugger on board).

Tips

• MPLAB IDE is sluggish with never ending suspended task Scan for external changes. Plase see https://stackoverflow.com/questions/6268031/how-can-i-disable-scan-for-external-changes-in-netbeans#6268263 for workaround
• suden Connection failed. error when programming board. Simply disconnect and connect again USB to PKOB (J20). It should start working again.