Fix: Using a delay(1) statement causes a minimum delay of 1 microsecond between two consecutive 8-bit data bursts.

aentinger · aentinger · commit 6820324909dc · 2022-09-08T06:28:54.000+02:00
This is turning the high-data-rate SPI bus into a very slow-data-rate bus.
diff --git a/libraries/SPI/SPI.cpp b/libraries/SPI/SPI.cpp
@@ -180,7 +180,7 @@ uint8_t ArduinoSPI::transfer(uint8_t data) {
   while ((SPI_EVENT_TRANSFER_COMPLETE != _spi_cb_event[_cb_event_idx]) && timeout_ms)
   {
       timeout_ms--;
-      delay(1);
+      __NOP();
   }
   if (SPI_EVENT_TRANSFER_ABORTED == _spi_cb_event[_cb_event_idx])
   {
@@ -201,7 +201,7 @@ uint16_t ArduinoSPI::transfer16(uint16_t data) {
   while ((SPI_EVENT_TRANSFER_COMPLETE != _spi_cb_event[_cb_event_idx]) && timeout_ms)
   {
       timeout_ms--;
-      delay(1);
+      __NOP();
   }
   if (SPI_EVENT_TRANSFER_ABORTED == _spi_cb_event[_cb_event_idx])
   {
@@ -221,7 +221,7 @@ void ArduinoSPI::transfer(void *buf, size_t count) {
   while ((SPI_EVENT_TRANSFER_COMPLETE != _spi_cb_event[_cb_event_idx]) && timeout_ms)
   {
       timeout_ms--;
-      delay(1);
+      __NOP();
   }
   if (SPI_EVENT_TRANSFER_ABORTED == _spi_cb_event[_cb_event_idx])
   {

Original file line number	Diff line number	Diff line change
`@@ -180,7 +180,7 @@ uint8_t ArduinoSPI::transfer(uint8_t data) {`
`180`	`180`	`while ((SPI_EVENT_TRANSFER_COMPLETE != _spi_cb_event[_cb_event_idx]) && timeout_ms)`
`181`	`181`	`{`
`182`	`182`	`timeout_ms--;`
`183`		`- delay(1);`
	`183`	`+ __NOP();`
`184`	`184`	`}`
`185`	`185`	`if (SPI_EVENT_TRANSFER_ABORTED == _spi_cb_event[_cb_event_idx])`
`186`	`186`	`{`
`@@ -201,7 +201,7 @@ uint16_t ArduinoSPI::transfer16(uint16_t data) {`
`201`	`201`	`while ((SPI_EVENT_TRANSFER_COMPLETE != _spi_cb_event[_cb_event_idx]) && timeout_ms)`
`202`	`202`	`{`
`203`	`203`	`timeout_ms--;`
`204`		`- delay(1);`
	`204`	`+ __NOP();`
`205`	`205`	`}`
`206`	`206`	`if (SPI_EVENT_TRANSFER_ABORTED == _spi_cb_event[_cb_event_idx])`
`207`	`207`	`{`
`@@ -221,7 +221,7 @@ void ArduinoSPI::transfer(void *buf, size_t count) {`
`221`	`221`	`while ((SPI_EVENT_TRANSFER_COMPLETE != _spi_cb_event[_cb_event_idx]) && timeout_ms)`
`222`	`222`	`{`
`223`	`223`	`timeout_ms--;`
`224`		`- delay(1);`
	`224`	`+ __NOP();`
`225`	`225`	`}`
`226`	`226`	`if (SPI_EVENT_TRANSFER_ABORTED == _spi_cb_event[_cb_event_idx])`
`227`	`227`	`{`