firmware_v2 speed improvements

* Run the XMEGA at 48 MHz
* Read only 2 bytes instead of 4
* Other attempts at improving speed

firmware_v2/main.c

@@ -129,6 +129,7 @@ int main(void)
 			CDC_Device_USBTask(&VirtualSerial_CDC_Interface);
 			USB_USBTask();
 			doUSBTask = false;
+			PORTC.OUT ^= (1 << 0);
 		}
 
 	}
@@ -169,29 +170,27 @@ void ADC_Init()
 
 static uint8_t spi_rx_buf[4];
 
-inline uint16_t ADC_Read(void)
+__attribute__((always_inline)) inline void ADC_Read(uint8_t * dest)
 {
 	while(!(PORTC.IN &= (1 << ADC_RVSPIN)));
 	PORTC.OUT &= ~(1 << 4);
-	spi_rx_buf[3] = SPI_ReceiveByte(&SPIC);
-	spi_rx_buf[2] = SPI_ReceiveByte(&SPIC);
-	spi_rx_buf[1] = SPI_ReceiveByte(&SPIC);
-	spi_rx_buf[0] = SPI_ReceiveByte(&SPIC);
+	*(dest + 1) = SPI_ReceiveByte(&SPIC);
+	*dest = SPI_ReceiveByte(&SPIC);
+	//spi_rx_buf[1] = SPI_ReceiveByte(&SPIC);
+	//spi_rx_buf[0] = SPI_ReceiveByte(&SPIC);
 	PORTC.OUT |= (1 << 4);
-
-	//return (uint32_t) *(uint32_t*)spi_rx_buf;
-	return (uint16_t) ((*(uint16_t*)(spi_rx_buf+2)) >> 4) ;
 }
 
 void ADC_Read_Block(void)
 {
 	TCC0.INTCTRLA = TC_OVFINTLVL_OFF_gc;
-	PORTC.OUT &= ~(1 << 0);
-	for(int i = 0; i < ADC_BUFSZ; i++)
+	// PORTC.OUT &= ~(1 << 0);
+
+	for(uint8_t * p = (uint8_t*)adc_buf; p < (uint8_t*)(adc_buf + ADC_BUFSZ); p += 2)
 	{
-		adc_buf[i] = ADC_Read();
+		ADC_Read(p);
 	}
-	PORTC.OUT |= (1 << 0);
+	// PORTC.OUT |= (1 << 0);
 	TCC0.INTCTRLA = TC_OVFINTLVL_LO_gc;
 }
 
@@ -227,7 +226,7 @@ void SetupHardware(void)
 
 	/* set up 25ms USB interrupt */
 	TCC0.CTRLA = TC_CLKSEL_DIV256_gc;
-	TCC0.PER = 3125;
+	TCC0.PER = F_CPU / 256 / 40;
 	TCC0.INTCTRLA = TC_OVFINTLVL_LO_gc;
 	TCC0.INTFLAGS = 0x01;
 	TCC0.CTRLB = TC_WGMODE_NORMAL_gc;

firmware_v2/main.h

@@ -53,7 +53,7 @@
 		uint8_t ReadSignatureByte(uint16_t);
 
 		void ADC_Init(void);
-		uint16_t ADC_Read(void);
+		void ADC_Read(uint8_t * dest);
 		void ADC_Read_Block(void);
 
 		void SetupHardware(void);

firmware_v2/makefile

@@ -14,9 +14,9 @@
 MCU          = atxmega16a4u
 ARCH         = XMEGA
 BOARD        = USBKEY
-F_CPU        = 32000000
+F_CPU        = 48000000
 F_USB        = 48000000
-OPTIMIZATION = s
+OPTIMIZATION = 3
 TARGET       = main
 SRC          = $(TARGET).c Descriptors.c $(LUFA_SRC_USB) $(LUFA_SRC_USBCLASS)
 LUFA_PATH    = /home/atomicinf/src/lufa-LUFA-170418/LUFA

plotter/main.py

@@ -46,6 +46,7 @@ def idle(parent, canvas):
             continue
 
         buf = np.frombuffer(tmp, dtype=np.uint16, count=512)
+        buf = buf >> 4
         break
 
     ax.clear()