SX126x cannot wake from sleep

[BarryPSmith]

Describe the bug
SX126x modules cannot be woken with the library, instead one must manually wake the unit with a digital write to its select pin.

It looks like in SX126x::SPItransfer, moving the line digitalWrite(_mod->getCs(), LOW); to run before the Wait for BUSY loop will fix this (first sentence in datasheet section 8.2.2) but I'm not sure if there's a reason it needs to be where it is.

To Reproduce

#include <RadioLib.h>

#define LORA_CHECK(A) { auto res = A; if(res) { Serial.print("FAILED " #A ": "); Serial.println(res); } } while(0)

#define BUSY 4
#define DIO1 2
#define DIO2 -1
#define SELECT 9
SX1262 lora = new Module(SELECT, DIO1, DIO2, BUSY);

void setup() {
  Serial.begin(9600);
  delay(10);
  LORA_CHECK(lora.begin());
  LORA_CHECK(lora.sleep());
  //digitalWrite(SELECT, LOW); //Uncomment this and everything works
  LORA_CHECK(lora.standby()); //Fails with -705
  Serial.println("Setup done. If no errors show, everything worked.");
}

void loop() {}

Expected behavior
The module can be woken from sleep by asking it to return to standby

Additional info (please complete):

• MCU: Ardiuno Nano
• Wireless module type: SX1262
• Arduino IDE version: 1.8.10
• Library version: tip of trunk as of writing. Checkin 300e7f4

[jgromes]

I was able to reproduce this, thanks.

You're right, NSS must go low before checking BUSY pin. BUSY should be held high in sleep mode, and since we wait for BUSY to go low at the start of SX126x::SPItranscation(), it will never leave the waiting loop, hence the timeout.

I'm not entirely sure why is NSS pulled low after checking BUSY pin - I think it might have been an effort to not start any SPI transactions as long as BUSY is high.

Will fix in a second.

[jgromes]

Fixed in 3db5134, thanks for reporting!