(2/3) Add Slow Clock Support for RP2040 platform. This will disable USB Softserial.

arch/rp2040/rp2040.ini

@@ -1,8 +1,8 @@
 ; Common settings for rp2040 Processor based targets
 [rp2040_base]
-platform = https://github.com/maxgerhardt/platform-raspberrypi.git#612de5399d68b359053f1307ed223d400aea975c
+platform = https://github.com/maxgerhardt/platform-raspberrypi.git#60d6ae81fcc73c34b1493ca9e261695e471bc0c2
 extends = arduino_base
-platform_packages = framework-arduinopico@https://github.com/earlephilhower/arduino-pico.git#3.6.2
+platform_packages = framework-arduinopico@https://github.com/earlephilhower/arduino-pico.git#3.7.2
 
 board_build.core = earlephilhower
 board_build.filesystem_size = 0.5m

src/SerialConsole.cpp

@@ -3,7 +3,11 @@
 #include "PowerFSM.h"
 #include "configuration.h"
 
+#ifdef RP2040_SLOW_CLOCK
+#define Port Serial2
+#else
 #define Port Serial
+#endif
 // Defaulting to the formerly removed phone_timeout_secs value of 15 minutes
 #define SERIAL_CONNECTION_TIMEOUT (15 * 60) * 1000UL
 
@@ -31,6 +35,10 @@ SerialConsole::SerialConsole() : StreamAPI(&Port), RedirectablePrint(&Port), con
     canWrite = false; // We don't send packets to our port until it has talked to us first
                       // setDestination(&noopPrint); for testing, try turning off 'all' debug output and see what leaks
 
+#ifdef RP2040_SLOW_CLOCK
+    Port.setTX(SERIAL2_TX);
+    Port.setRX(SERIAL2_RX);
+#endif
     Port.begin(SERIAL_BAUD);
 #if defined(ARCH_NRF52) || defined(CONFIG_IDF_TARGET_ESP32S2) || defined(CONFIG_IDF_TARGET_ESP32S3) || defined(ARCH_RP2040)
     time_t timeout = millis();

src/modules/SerialModule.cpp

@@ -126,8 +126,13 @@ int32_t SerialModule::runOnce()
             uint32_t baud = getBaudRate();
 
             if (moduleConfig.serial.override_console_serial_port) {
+#ifdef RP2040_SLOW_CLOCK
+                Serial2.flush();
+                serialPrint = &Serial2;
+#else
                 Serial.flush();
                 serialPrint = &Serial;
+#endif
                 // Give it a chance to flush out 💩
                 delay(10);
             }
@@ -151,8 +156,13 @@ int32_t SerialModule::runOnce()
                 Serial2.begin(baud, SERIAL_8N1);
                 Serial2.setTimeout(moduleConfig.serial.timeout > 0 ? moduleConfig.serial.timeout : TIMEOUT);
             } else {
+#ifdef RP2040_SLOW_CLOCK
+                Serial2.begin(baud, SERIAL_8N1);
+                Serial2.setTimeout(moduleConfig.serial.timeout > 0 ? moduleConfig.serial.timeout : TIMEOUT);
+#else
                 Serial.begin(baud, SERIAL_8N1);
                 Serial.setTimeout(moduleConfig.serial.timeout > 0 ? moduleConfig.serial.timeout : TIMEOUT);
+#endif
             }
 #else
             Serial.begin(baud, SERIAL_8N1);

src/platform/rp2040/main-rp2040.cpp

@@ -1,4 +1,7 @@
 #include "configuration.h"
+#include <hardware/clocks.h>
+#include <hardware/pll.h>
+#include <pico/stdlib.h>
 #include <pico/unique_id.h>
 #include <stdio.h>
 
@@ -35,9 +38,56 @@ void rp2040Setup()
        Taken from CPU cycle counter and ROSC oscillator, so should be pretty random.
     */
     randomSeed(rp2040.hwrand32());
+
+#ifdef RP2040_SLOW_CLOCK
+    uint f_pll_sys = frequency_count_khz(CLOCKS_FC0_SRC_VALUE_PLL_SYS_CLKSRC_PRIMARY);
+    uint f_pll_usb = frequency_count_khz(CLOCKS_FC0_SRC_VALUE_PLL_USB_CLKSRC_PRIMARY);
+    uint f_rosc = frequency_count_khz(CLOCKS_FC0_SRC_VALUE_ROSC_CLKSRC);
+    uint f_clk_sys = frequency_count_khz(CLOCKS_FC0_SRC_VALUE_CLK_SYS);
+    uint f_clk_peri = frequency_count_khz(CLOCKS_FC0_SRC_VALUE_CLK_PERI);
+    uint f_clk_usb = frequency_count_khz(CLOCKS_FC0_SRC_VALUE_CLK_USB);
+    uint f_clk_adc = frequency_count_khz(CLOCKS_FC0_SRC_VALUE_CLK_ADC);
+    uint f_clk_rtc = frequency_count_khz(CLOCKS_FC0_SRC_VALUE_CLK_RTC);
+
+    LOG_INFO("Clock speed:\n");
+    LOG_INFO("pll_sys  = %dkHz\n", f_pll_sys);
+    LOG_INFO("pll_usb  = %dkHz\n", f_pll_usb);
+    LOG_INFO("rosc     = %dkHz\n", f_rosc);
+    LOG_INFO("clk_sys  = %dkHz\n", f_clk_sys);
+    LOG_INFO("clk_peri = %dkHz\n", f_clk_peri);
+    LOG_INFO("clk_usb  = %dkHz\n", f_clk_usb);
+    LOG_INFO("clk_adc  = %dkHz\n", f_clk_adc);
+    LOG_INFO("clk_rtc  = %dkHz\n", f_clk_rtc);
+#endif
 }
 
 void enterDfuMode()
 {
     reset_usb_boot(0, 0);
 }
+
+/* Init in early boot state. */
+#ifdef RP2040_SLOW_CLOCK
+void initVariant()
+{
+    /* Set the system frequency to 18 MHz. */
+    set_sys_clock_khz(18 * KHZ, false);
+    /* The previous line automatically detached clk_peri from clk_sys, and
+       attached it to pll_usb. We need to attach clk_peri back to system PLL to keep SPI
+       working at this low speed.
+       For details see https://github.com/jgromes/RadioLib/discussions/938
+    */
+    clock_configure(clk_peri,
+                    0,                                                // No glitchless mux
+                    CLOCKS_CLK_PERI_CTRL_AUXSRC_VALUE_CLKSRC_PLL_SYS, // System PLL on AUX mux
+                    18 * MHZ,                                         // Input frequency
+                    18 * MHZ                                          // Output (must be same as no divider)
+    );
+    /* Run also ADC on lower clk_sys. */
+    clock_configure(clk_adc, 0, CLOCKS_CLK_ADC_CTRL_AUXSRC_VALUE_CLKSRC_PLL_SYS, 18 * MHZ, 18 * MHZ);
+    /* Run RTC from XOSC since USB clock is off */
+    clock_configure(clk_rtc, 0, CLOCKS_CLK_RTC_CTRL_AUXSRC_VALUE_XOSC_CLKSRC, 12 * MHZ, 47 * KHZ);
+    /* Turn off USB PLL */
+    pll_deinit(pll_usb);
+}
+#endif