Use timeout when waiting for dreq in sci mode

Default timeout (50ms) chosen, such that all sci operations have completed
within the chosen timeout. See datasheet, p.38.

Author: episource

src/VS1053.cpp

@@ -40,22 +40,24 @@ uint16_t VS1053::read_register(uint8_t _reg) const {
     uint16_t result;
 
     control_mode_on();
-    SPI.write(3);    // Read operation
-    SPI.write(_reg); // Register to write (0..0xF)
+    await_data_request_with_timeout();
+    spi_write(3);    // Read operation
+    spi_write(_reg); // Register to write (0..0xF)
     // Note: transfer16 does not seem to work
     result = (SPI.transfer(0xFF) << 8) | // Read 16 bits data
              (SPI.transfer(0xFF));
-    await_data_request(); // Wait for DREQ to be HIGH again
+    await_data_request_with_timeout(); // Wait for DREQ to be HIGH again
     control_mode_off();
     return result;
 }
 
 void VS1053::writeRegister(uint8_t _reg, uint16_t _value) const {
     control_mode_on();
-    SPI.write(2);        // Write operation
-    SPI.write(_reg);     // Register to write (0..0xF)
-    SPI.write16(_value); // Send 16 bits data
-    await_data_request();
+    await_data_request_with_timeout();
+    spi_write(2);        // Write operation
+    spi_write(_reg);     // Register to write (0..0xF)
+    spi_write16(_value); // Send 16 bits data
+    await_data_request_with_timeout();
     control_mode_off();
 }
 

src/VS1053.h

@@ -91,6 +91,15 @@ class VS1053 {
         }
     }
 
+    // min CLKI is 12MHZ, max time until dreq high is 450CLKI (data sheet p. 38)
+    // => dreq timeout 50ms is on the safe side
+    inline void await_data_request_with_timeout(uint32_t timeoutMs = 50) const {
+        uint32_t absTimeoutMs = millis() + timeoutMs;
+        while (!digitalRead(dreq_pin) && absTimeoutMs < millis()) {
+            yield();
+        }
+    }
+
     inline void control_mode_on() const {
         SPI.beginTransaction(VS1053_SPI);   // Prevent other SPI users
         digitalWrite(dcs_pin, HIGH);        // Bring slave in control mode