Add examples for polling DMA transfers.

Only in the SPI case, but the I2S case has the same API so this should
be fine.

CHANGELOG.md

@@ -27,6 +27,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Add some miscellaneous examples for the ESP32-H2 (#548)
 - Add initial support for PCNT in ESP32-H2 (#551)
 - Add initial support for RMT in ESP32-H2 (#556)
+- Add a fn to poll DMA transfers
 
 ### Fixed
 

esp32-hal/examples/spi_loopback_dma.rs

@@ -98,6 +98,13 @@ fn main() -> ! {
 
         let transfer = spi.dma_transfer(send, receive).unwrap();
         // here we could do something else while DMA transfer is in progress
+        let mut i = 0;
+        // Check is_done until the transfer is almost done (32000 bytes at 100kHz is
+        // 2.56 seconds), then move to wait().
+        while !transfer.is_done() && i < 10 {
+            delay.delay_ms(250u32);
+            i += 1;
+        }
         // the buffers and spi is moved into the transfer and we can get it back via
         // `wait`
         (receive, send, spi) = transfer.wait();

esp32c2-hal/examples/spi_loopback_dma.rs

@@ -99,6 +99,13 @@ fn main() -> ! {
 
         let transfer = spi.dma_transfer(send, receive).unwrap();
         // here we could do something else while DMA transfer is in progress
+        let mut i = 0;
+        // Check is_done until the transfer is almost done (32000 bytes at 100kHz is
+        // 2.56 seconds), then move to wait().
+        while !transfer.is_done() && i < 10 {
+            delay.delay_ms(250u32);
+            i += 1;
+        }
         // the buffers and spi is moved into the transfer and we can get it back via
         // `wait`
         (receive, send, spi) = transfer.wait();

esp32c3-hal/examples/spi_loopback_dma.rs

@@ -106,6 +106,13 @@ fn main() -> ! {
 
         let transfer = spi.dma_transfer(send, receive).unwrap();
         // here we could do something else while DMA transfer is in progress
+        let mut i = 0;
+        // Check is_done until the transfer is almost done (32000 bytes at 100kHz is
+        // 2.56 seconds), then move to wait().
+        while !transfer.is_done() && i < 10 {
+            delay.delay_ms(250u32);
+            i += 1;
+        }
         // the buffers and spi is moved into the transfer and we can get it back via
         // `wait`
         (receive, send, spi) = transfer.wait();

esp32c6-hal/examples/spi_loopback_dma.rs

@@ -107,6 +107,13 @@ fn main() -> ! {
 
         let transfer = spi.dma_transfer(send, receive).unwrap();
         // here we could do something else while DMA transfer is in progress
+        let mut i = 0;
+        // Check is_done until the transfer is almost done (32000 bytes at 100kHz is
+        // 2.56 seconds), then move to wait().
+        while !transfer.is_done() && i < 10 {
+            delay.delay_ms(250u32);
+            i += 1;
+        }
         // the buffers and spi is moved into the transfer and we can get it back via
         // `wait`
         (receive, send, spi) = transfer.wait();

esp32s2-hal/examples/spi_loopback_dma.rs

@@ -98,6 +98,13 @@ fn main() -> ! {
 
         let transfer = spi.dma_transfer(send, receive).unwrap();
         // here we could do something else while DMA transfer is in progress
+        let mut i = 0;
+        // Check is_done until the transfer is almost done (32000 bytes at 100kHz is
+        // 2.56 seconds), then move to wait().
+        while !transfer.is_done() && i < 10 {
+            delay.delay_ms(250u32);
+            i += 1;
+        }
         // the buffers and spi is moved into the transfer and we can get it back via
         // `wait`
         (receive, send, spi) = transfer.wait();

esp32s3-hal/examples/spi_loopback_dma.rs

@@ -106,6 +106,13 @@ fn main() -> ! {
 
         let transfer = spi.dma_transfer(send, receive).unwrap();
         // here we could do something else while DMA transfer is in progress
+        let mut i = 0;
+        // Check is_done until the transfer is almost done (32000 bytes at 100kHz is
+        // 2.56 seconds), then move to wait().
+        while !transfer.is_done() && i < 10 {
+            delay.delay_ms(250u32);
+            i += 1;
+        }
         // the buffers and spi is moved into the transfer and we can get it back via
         // `wait`
         (receive, send, spi) = transfer.wait();