radio.begin() hangs on raspberry pi pico since b5a905b

[felher]

Hey all!

When using the library on my raspbery pi pico, calling radio.begin() hangs forever. This was not always the case. I used a former version of this library in an older project and it worked fine. I run a git bisect with the version I had used in the old project and it seems that since commit b5a905b, calling radio.begin() just hangs.

Here is a minmal code example:

#define CE_PIN 7
#define CSN_PIN 8
#define IRQ_PIN 6

#include <RF24.h> // RF24 radio object

RF24 radio(CE_PIN, CSN_PIN);

int main() {
  const uint8_t LED_PIN = 25;
  stdio_init_all();
  gpio_init(LED_PIN);
  gpio_set_dir(LED_PIN, GPIO_OUT);

  radio.begin();

  while (true) {
    gpio_put(LED_PIN, 1);
    sleep_ms(100);
    gpio_put(LED_PIN, 0);
    sleep_ms(100);
  }
}

I did expect to see blinking, but I'm not seeing any. If I remove the radio.begin() line, the LED starts to blink again. If I reset library to a version before b5a905b I can leave radio.begin() in and it works fine.

I'm not an expert by any stretch, so this might well be an misunderstanding/mistake on my part. If so, I apologize for the spurious bug report

[2bndy5]

There isn't any loops in RF24::begin() that would cause a hang. So I think this may be related to the arduino-wrapping SPI code that uses the PicoSDK's spi_write_read_blocking().

The only reason I can think of is if the specified SPI bus interface isn't initialized correctly (via spi_init() from our wrapping function SPI::beginTransaction()).

I'm not at home yet, but soon I'll spin up 1 of our lib's examples_pico binaries to try and reproduce.

[2bndy5]

The mentioned commit neglects

RF24/utility/rp2/RF24_arch_config.h

Line 31 in da89874

static SPI spi;

which is the SPI instance that RF24 uses by default.

Maybe, the removal of static attributes requires the object be instantiated like so

SPI spi = SPI();

[2bndy5]

yep, we didn't thoroughly test the default RF24::begin() from that commit... I got it working with the following patch:

diff --git a/RF24.cpp b/RF24.cpp
index c0ceef8a..68144a25 100644
--- a/RF24.cpp
+++ b/RF24.cpp
@@ -999,6 +999,7 @@ bool RF24::begin(void)
     _spi->begin(csn_pin);

 #elif defined(RF24_RP2)
+    _spi = new SPI();
     _spi->begin(PICO_DEFAULT_SPI ? spi1 : spi0);

 #else // using an Arduino platform || defined (LITTLEWIRE)
diff --git a/utility/rp2/RF24_arch_config.h b/utility/rp2/RF24_arch_config.h
index 7d5a1a93..3f24e949 100644
--- a/utility/rp2/RF24_arch_config.h
+++ b/utility/rp2/RF24_arch_config.h
@@ -28,8 +28,6 @@
 #define _SPI   SPI
 #define RF24_SPI_PTR

-static SPI spi;
-
 #ifdef SERIAL_DEBUG
     #define IF_SERIAL_DEBUG(x) ({ x; })
 #else

However, I'm not receiving any data, only sending data works. This might be a separate issue with my RPi4 setup, so I'll try again with a different device... I'm testing the examples_pico/getting_started.cpp on my Feather RP2040.

[2bndy5]

However, I'm not receiving any data, only sending data works

It wasn't my RPi setup, it was the adapter board I had connecting my nRF24 module to my Feather RP2040. This above patch works fine to fix this regression

@felher I pushed the fix to the master branch, so you should be good to go now

[felher]

Holy moly, this was fast! Thank you!

[TMRh20]

That was fast! You rock @2bndy5