10000 Communication with cyw43 fails at system clock speeds <= 60MHz · Issue #1392 · raspberrypi/pico-sdk · GitHub
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Communication with cyw43 fails at system clock speeds <= 60MHz #1392

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MichaelBell opened this issue May 25, 2023 · 2 comments
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Communication with cyw43 fails at system clock speeds <= 60MHz #1392

MichaelBell opened this issue May 25, 2023 · 2 comments
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@peterharperuk
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cyw43_driver
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2.0.0

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@MichaelBell
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It's sometimes useful to run the RP2040 quite slowly to reduce power consumption. I'm not sure whether it is reasonable to expect Wifi to continue to work at low clock speeds - but I think it is reasonable to at least expect to be able to use the CYW43 GPIO.

However, at around 60MHz and below setting/reading the GPIO from the CYW43 doesn't work. This means you can't determine whether VBUS is present, and can't control the LED.

A simple repro is to add set_sys_clock_48mhz() to the top of the pico_w blink example.

index 149b477..600e2a2 100644
--- a/pico_w/wifi/blink/picow_blink.c
+++ b/pico_w/wifi/blink/picow_blink.c
@@ -8,6 +8,7 @@
 #include "pico/cyw43_arch.h"

 int main() {
+    set_sys_clock_48mhz();
     stdio_init_all();
     if (cyw43_arch_init()) {
         printf("Wi-Fi init failed");
@MichaelBell MichaelBell mentioned this issue May 25, 2023
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@kilograham kilograham added this to the 1.6.0 milestone May 26, 2023
@Gadgetoid Gadgetoid mentioned this issue Jul 19, 2023
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ai6aj added a commit to ai6aj/pico-sdk that referenced this issue Oct 21, 2023
@ai6aj
Add cyw43_spi_set_clock_divisor() to allow CYW43
4709b06 
to work when over/underclocking the RP2040
Addresses issues raspberrypi#1297 and raspberrypi#1392
@ai6aj ai6aj mentioned this issue Oct 22, 2023
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@lurch lurch mentioned this issue Oct 22, 2023
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@mvds00
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mvds00 commented Oct 23, 2023

WiFi works flawlessly for us with the Pi Pico running at 12 MHz from xosc. Set clock divider at 1 and spi program spi_gap01_sample0. Running at 48 MHz (to enable USB stdio) clock divider 2 and spi program spi_gap0_sample1 can be used, IIRC.

@kilograham kilograham modified the milestones: 1.6.1, 1.6.0 May 19, 2024
@kilograham kilograham modified the milestones: 1.6.0, 1.6.2, 1.6.1 Jul 21, 2024
@peterharperuk peterharperuk modified the milestones: 1.6.1, 1.6.2 Jul 24, 2024
@kilograham kilograham modified the milestones: 1.6.2, 2.0.0 Aug 8, 2024
@peterharperuk
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I seem to be able to be able to use cyw43 to flash the led when running from xosc by calling the new function cyw43_set_pio_clock_divisor(1, 0). I didn't seem to have to set CYW43_SPI_PROGRAM_NAME? Anyway - I think this is resolved now as you shouldn't have to hack the code?

@Gadgetoid Gadgetoid mentioned this issue Feb 25, 2025
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