What is the best way to configure the external clock?

[rtek1000]

Hello,

I read that the CH32V203C8T6's internal clock (HSI) can have about a 2.2% tolerance (In 1 hour the clock can reach about 72 seconds of deviation?)

I would like to replace a PIC16F873A and would like to use the 4 MHz crystal present on the board.

What is the best way to configure the external clock, since there is no configuration option in the Tools tab of the Arduino IDE?

[rtek1000]

I found the file system_ch32v20x.c

(located in .arduino15/packages/WCH/hardware/ch32v/1.0.4/system/CH32V20x/USER/system_ch32v20x.c).

I noticed that if I select HSE 144MHz, it does the multiplication of 18x, that is, 144MHz / 18 is 8MHz.

#define SYSCLK_FREQ_144MHz_HSE 144000000

SetSysClockTo144_HSE()

If 18x is the maximum multiplication factor. Then with only 4MHz the maximum is 72MHz (4MHz x18).

Then I copied the sub SetSysClockTo72_HSE() and created the sub SetSysClockTo72_HSE_4MHz(). I changed the multiplication factor from 9x to 18x.

Selecting SYSCLK_FREQ_72MHz_HSE_4MHz I now have 72MHz with 4MHz crystal.

#define SYSCLK_FREQ_72MHz_HSE_4MHz 72000000

If anyone wants to see it, it is attached.

system_ch32v20x.c

[rtek1000]

Another note: if someone tries to change the clock, and the WCH-linkE programmer stops finding the CH32V203 microcontroller:

• It may be necessary to change the BOOT0 jumper to high.
• Upload the correct program (The programmer can write, but it will give an error during verification).
• Then just return BOOT0 to low, and the next time you upload, it should be normal).

[maxint-rd]

What is the best way to configure the external clock, since there is no
configuration option in the Tools tab of the Arduino IDE?

As you seem to already found out: the v1.0.4 is outdated. The latest master branch code includes selection of clock speed via the IDE menu. The issue of clock selection is a bit old. See #27 and #66. There were also some issues related to capitalization of used constants. I'm not quite sure in what commit the clock menu was added. Note that the master branch includes some quite useful PR's that have been merged. Other (still unmerged) PR's may be useful too.

BTW. In my local installation I also added selection of peripheral devices to the menu. I included those changes in PR #200 (changes made for V003/VM00X/X033, not for other family members since I can't test those).

[rtek1000]

One note: the compiler shows 144MHz even though it was manually set to 72MHz:

Processing genericCH32V203C8T6 (platform: ch32v; board: genericCH32V203C8T6; framework: arduino)

Verbose mode can be enabled via -v, --verbose option
CONFIGURATION: https://docs.platformio.org/page/boards/ch32v/genericCH32V203C8T6.html
PLATFORM: WCH CH32V (1.1.0+sha.0eedcf6) > Generic CH32V203C8T6
HARDWARE: CH32V203C8T6 144MHz, 20KB RAM, 64KB Flash
DEBUG: Current (wch-link) On-board (wch-link) External (minichlink)
PACKAGES:

• framework-arduino-openwch-ch32 @ 0.0.0+sha.a4e27b6
• tool-openocd-riscv-wch @ 2.1100.240729 (11.0)
• tool-wlink @ 0.23.241116+sha.fb3a0c6
• toolchain-riscv @ 1.120200.220829+sha.fde267f
  Clock configuration:
  Source: hsi+pll
  Frequency: 144000000 Hz
  Macro: SYSCLK_FREQ_144MHz_HSI=144000000

I found a possible relationship with the file:
/home/user/.platformio/platforms/ch32v/builder/frameworks/common_clk_config.py

Using the command line:
grep -rnw '/home/user/.platformio/' -e 'Clock configuration'

I found the file that selects the parameters informed when compiling:
/home/user/.platformio/platforms/ch32v/boards/genericCH32V203C8T6.json

Processing genericCH32V203C8T6 (platform: ch32v; board: genericCH32V203C8T6; framework: arduino)

Verbose mode can be enabled via -v, --verbose option
CONFIGURATION: https://docs.platformio.org/page/boards/ch32v/genericCH32V203C8T6.html
PLATFORM: WCH CH32V (1.1.0+sha.0eedcf6) > Generic CH32V203C8T6
HARDWARE: CH32V203C8T6 72MHz, 20KB RAM, 64KB Flash
DEBUG: Current (wch-link) On-board (wch-link) External (minichlink)
PACKAGES:

• framework-arduino-openwch-ch32 @ 0.0.0+sha.a4e27b6
• tool-openocd-riscv-wch @ 2.1100.240729 (11.0)
• tool-wlink @ 0.23.241116+sha.fb3a0c6
• toolchain-riscv @ 1.120200.220829+sha.fde267f
  Clock configuration:
  Source: hse+pll
  Frequency: 72000000 Hz
  Macro: SYSCLK_FREQ_72MHz_HSE=72000000