diff --git a/pio/pio_blink/blink.c b/pio/pio_blink/blink.c
index 6187186b2..f5eecf9ca 100644
--- a/pio/pio_blink/blink.c
+++ b/pio/pio_blink/blink.c
@@ -11,78 +11,103 @@
 #include "hardware/clocks.h"
 #include "blink.pio.h"
 
+/**
+ * This example demonstrates using PIO to flash four LEDs at different frequencies.
+ * On RP2040 and RP2350A those GPIOs are all in the same "PIO range" of 0 - 31 (so a single PIO is used).
+ * On RP2350B the first two GPIOs are in the "lower PIO range" of 0 - 31 and the
+ * next two LEDs are in the "higher PIO range" of 16 - 47 (so two PIOs are used).
+ */
+
 void blink_pin_forever(PIO pio, uint sm, uint offset, uint pin, uint freq);
 
-// by default flash leds on gpios 3-4
+// By default flash LEDs on GPIOs 3 and 4
 #ifndef PIO_BLINK_LED1_GPIO
 #define PIO_BLINK_LED1_GPIO 3
+#define PIO_BLINK_LED2_GPIO (PIO_BLINK_LED1_GPIO + 1)
 #endif
 
-// and flash leds on gpios 5-6
-// or if the device supports more than 32 gpios, flash leds on 32-33
+// and also flash LEDs on GPIOs 5 and 6
+// Or if the device has more than 32 gpios, also flash LEDs on GPIOs 32 and 33
 #ifndef PIO_BLINK_LED3_GPIO
 #if NUM_BANK0_GPIOS <= 32
 #define PIO_BLINK_LED3_GPIO 5
 #else
 #define PIO_BLINK_LED3_GPIO 32
 #endif
+#define PIO_BLINK_LED4_GPIO (PIO_BLINK_LED3_GPIO + 1)
 #endif
 
+#define PIO_BLINK_LED1_FREQUENCY 4
+#define PIO_BLINK_LED2_FREQUENCY 3
+#define PIO_BLINK_LED3_FREQUENCY 2
+#define PIO_BLINK_LED4_FREQUENCY 1
+
 int main() {
     setup_default_uart();
 
-    assert(PIO_BLINK_LED1_GPIO < 31);
-    assert(PIO_BLINK_LED3_GPIO < 31 || PIO_BLINK_LED3_GPIO >= 32);
-
+    // LED1 and LED2 are both expected to be in the "lower" range of PIO-addressable GPIOs
+    assert(PIO_BLINK_LED2_GPIO == PIO_BLINK_LED1_GPIO + 1);
+    assert((PIO_BLINK_LED1_GPIO < 32) && (PIO_BLINK_LED2_GPIO < 32));
+    // check LED3 and LED4 are both in the same range of PIO-addressable GPIOs
+    assert(PIO_BLINK_LED4_GPIO == PIO_BLINK_LED3_GPIO + 1);
+    assert(((PIO_BLINK_LED3_GPIO < 32) && (PIO_BLINK_LED4_GPIO < 32)) || ((PIO_BLINK_LED3_GPIO >= 16) && (PIO_BLINK_LED3_GPIO < 48) && (PIO_BLINK_LED4_GPIO >= 16) && (PIO_BLINK_LED4_GPIO < 48)));
+
+    // LED1 and LED2 are both controlled by the program loaded into pio[0] at offset[0]
+    // LED3 and LED4 are both controlled by the program loaded into pio[1] at offset[1] (which might be the same as pio[0] and offset[0] if LED3 and LED4 are both on GPIOs < 32)
+    // LED1 is controlled by sm[0]
+    // LED2 is controlled by sm[1]
+    // LED3 is controlled by sm[2]
+    // LED4 is controlled by sm[3]
     PIO pio[2];
-    uint sm[2];
+    uint sm[4];
     uint offset[2];
 
-    // Find a free pio and state machine and add the program
+    // Find a free PIO and state machine and add the program
     bool rc = pio_claim_free_sm_and_add_program_for_gpio_range(&blink_program, &pio[0], &sm[0], &offset[0], PIO_BLINK_LED1_GPIO, 2, true);
     hard_assert(rc);
     printf("Loaded program at %u on pio %u\n", offset[0], PIO_NUM(pio[0]));
 
-    // Start led1 flashing
-    blink_pin_forever(pio[0], sm[0], offset[0], PIO_BLINK_LED1_GPIO, 4);
+    // Start LED1 flashing
+    blink_pin_forever(pio[0], sm[0], offset[0], PIO_BLINK_LED1_GPIO, PIO_BLINK_LED1_FREQUENCY);
 
-    // Claim the next state machine and start led2 flashing
-    pio_sm_claim(pio[0], sm[0] + 1);
-    blink_pin_forever(pio[0], sm[0] + 1, offset[0], PIO_BLINK_LED1_GPIO + 1, 3);
+    // Claim the next unused state machine and start LED2 flashing
+    sm[1] = pio_claim_unused_sm(pio[0], true);
+    blink_pin_forever(pio[0], sm[1], offset[0], PIO_BLINK_LED2_GPIO, PIO_BLINK_LED2_FREQUENCY);
 
-    if (PIO_BLINK_LED3_GPIO >= 32) {
-        // Find a free pio and state machine and add the program
-        rc = pio_claim_free_sm_and_add_program_for_gpio_range(&blink_program, &pio[1], &sm[1], &offset[1], PIO_BLINK_LED3_GPIO, 2, true);
+    if ((PIO_BLINK_LED3_GPIO >= 32) || (PIO_BLINK_LED4_GPIO >= 32)) {
+        // Find a free PIO and state machine and add the program
+        rc = pio_claim_free_sm_and_add_program_for_gpio_range(&blink_program, &pio[1], &sm[2], &offset[1], PIO_BLINK_LED3_GPIO, 2, true);
         printf("Loaded program at %u on pio %u\n", offset[1], PIO_NUM(pio[1]));
     } else {
         // no need to load the program again
         rc = true;
         pio[1] = pio[0];
-        sm[1] = sm[0] + 2;
         offset[1] = offset[0];
-        pio_sm_claim(pio[1], sm[1]);
+        sm[2] = pio_claim_unused_sm(pio[1], true);
     }
     hard_assert(rc);
 
-    // Start led3 flashing
-    blink_pin_forever(pio[1], sm[1], offset[1], PIO_BLINK_LED3_GPIO, 2);
+    // Start LED3 flashing
+    blink_pin_forever(pio[1], sm[2], offset[1], PIO_BLINK_LED3_GPIO, PIO_BLINK_LED3_FREQUENCY);
+
+    // Claim the next unused state machine and start LED4 flashing
+    sm[3] = pio_claim_unused_sm(pio[1], true);
+    blink_pin_forever(pio[1], sm[3], offset[1], PIO_BLINK_LED4_GPIO, PIO_BLINK_LED4_FREQUENCY);
 
-    // Claim the next state machine and start led4 flashing
-    pio_sm_claim(pio[1], sm[1] + 1);
-    blink_pin_forever(pio[1], sm[1] + 1, offset[1], PIO_BLINK_LED3_GPIO + 1, 1);
+    printf("All LEDs should be flashing\n");
 
-    // free up pio resources
-    pio_sm_unclaim(pio[1], sm[1] + 1);
-    if (PIO_BLINK_LED3_GPIO >= 32) {
-        pio_remove_program_and_unclaim_sm(&blink_program, pio[1], sm[1], offset[1]);
+    // free up PIO resources
+    pio_sm_unclaim(pio[1], sm[3]);
+    if ((PIO_BLINK_LED3_GPIO >= 32) || (PIO_BLINK_LED4_GPIO >= 32)) {
+        pio_remove_program_and_unclaim_sm(&blink_program, pio[1], sm[2], offset[1]);
     } else {
-        pio_sm_unclaim(pio[1], sm[1]);
+        pio_sm_unclaim(pio[1], sm[2]);
     }
-    pio_sm_unclaim(pio[0], sm[0] + 1);
+    pio_sm_unclaim(pio[0], sm[1]);
     pio_remove_program_and_unclaim_sm(&blink_program, pio[0], sm[0], offset[0]);
 
-    // the program exits but the pio keeps running!
-    printf("All leds should be flashing\n");
+    // the program exits but the PIO keeps running!
+    printf("All LEDs should continue to flash\n");
 }
 
 void blink_pin_forever(PIO pio, uint sm, uint offset, uint pin, uint freq) {