diff pru_rtaudio.p @ 12:a6beeba3a648

Initial support for higher matrix sample rates by reducing the number of channels. Input not tested yet, and not all examples updated to new format.

--- a/pru_rtaudio.p	Thu Nov 13 16:02:59 2014 +0100
+++ b/pru_rtaudio.p	Thu Jan 22 19:00:22 2015 +0000
@@ -80,6 +80,7 @@
 #define COMM_LED_PIN_MASK     28          // Which pin to write to change LED
 #define COMM_FRAME_COUNT      32	  // How many frames have elapse since beginning
 #define COMM_USE_SPI          36          // Whether or not to use SPI ADC and DAC
+#define COMM_NUM_CHANNELS     40	  // Low 2 bits indicate 8 [0x3], 4 [0x1] or 2 [0x0] channels
 	
 #define MCASP0_BASE 0x48038000
 #define MCASP1_BASE 0x4803C000
@@ -173,15 +174,17 @@
 #define MCASP_DATA_MASK 	0xFFFF		// 16 bit data
 #define MCASP_DATA_FORMAT	0x807C		// MSB first, 0 bit delay, 16 bits, CFG bus, ROR 16bits
 
-#define C_MCASP_MEM             C28     // Shared PRU mem
+#define C_MCASP_MEM             C28     	// Shared PRU mem
 
 // Flags for the flags register
 #define FLAG_BIT_BUFFER1	0
 #define FLAG_BIT_USE_SPI	1
+#define FLAG_BIT_MCASP_HWORD	2		// Whether we are on the high word for McASP transmission
 	
 // Registers used throughout
 
 // r1, r2, r3 are used for temporary storage
+#define reg_num_channels	r9		// Number of SPI ADC/DAC channels to use
 #define reg_frame_current	r10		// Current frame count in SPI ADC/DAC transfer
 #define reg_frame_total		r11		// Total frame count for SPI ADC/DAC
 #define reg_dac_data		r12		// Current dword for SPI DAC
@@ -356,6 +359,9 @@
       // Clear flags
       MOV reg_flags, 0
 
+      // Default number of channels in case SPI disabled
+      LDI reg_num_channels, 8
+	
       // Find out whether we should use SPI ADC and DAC
       LBBO r2, reg_comm_addr, COMM_USE_SPI, 4
       QBEQ SPI_FLAG_CHECK_DONE, r2, 0
@@ -364,6 +370,19 @@
 SPI_FLAG_CHECK_DONE:
       // If we don't use SPI, then skip all this init
       QBBC SPI_INIT_DONE, reg_flags, FLAG_BIT_USE_SPI
+
+      // Load the number of channels: valid values are 8, 4 or 2
+      LBBO reg_num_channels, reg_comm_addr, COMM_NUM_CHANNELS, 4
+      QBGT SPI_NUM_CHANNELS_LT8, reg_num_channels, 8 // 8 > num_channels ?
+      LDI reg_num_channels, 8		// If N >= 8, N = 8
+      QBA SPI_NUM_CHANNELS_DONE
+SPI_NUM_CHANNELS_LT8:	
+      QBGT SPI_NUM_CHANNELS_LT4, reg_num_channels, 4 // 4 > num_channels ?
+      LDI reg_num_channels, 4		// If N >= 4, N = 4
+      QBA SPI_NUM_CHANNELS_DONE
+SPI_NUM_CHANNELS_LT4:
+      LDI reg_num_channels, 2		// else N = 2
+SPI_NUM_CHANNELS_DONE:	
 	
       // Init SPI clock
       MOV r2, 0x02
@@ -491,11 +510,13 @@
 MCASP_REG_SET_BIT_AND_POLL MCASP_XGBLCTL, (1 << 12)	// Set XFRST
 
 // Initialisation
-LBBO reg_frame_total, reg_comm_addr, COMM_BUFFER_FRAMES, 4  // Total frame count (SPI; 2x for McASP)
+LBBO reg_frame_total, reg_comm_addr, COMM_BUFFER_FRAMES, 4  // Total frame count (SPI; 0.5x-2x for McASP)
 MOV reg_dac_buf0, 0                      // DAC buffer 0 start pointer
-LSL reg_dac_buf1, reg_frame_total, 4     // DAC buffer 1 start pointer = 8[ch]*2[bytes]*bufsize
+LSL reg_dac_buf1, reg_frame_total, 1     // DAC buffer 1 start pointer = N[ch]*2[bytes]*bufsize
+LMBD r2, reg_num_channels, 1		 // Returns 1, 2 or 3 depending on the number of channels
+LSL reg_dac_buf1, reg_dac_buf1, r2	 // Multiply by 2, 4 or 8 to get the N[ch] scaling above
 MOV reg_mcasp_buf0, 0			 // McASP DAC buffer 0 start pointer
-LSL reg_mcasp_buf1, reg_frame_total, 3   // McASP DAC buffer 1 start pointer = 2[ch]*2[bytes]*2[samples/spi]*bufsize
+LSL reg_mcasp_buf1, reg_frame_total, r2  // McASP DAC buffer 1 start pointer = 2[ch]*2[bytes]*(N/4)[samples/spi]*bufsize
 CLR reg_flags, reg_flags, FLAG_BIT_BUFFER1  // Bit 0 holds which buffer we are on
 MOV r2, 0
 SBBO r2, reg_comm_addr, COMM_FRAME_COUNT, 4  // Start with frame count of 0
@@ -521,16 +542,19 @@
       // Write a single buffer of DAC samples and read a buffer of ADC samples
       // Load starting positions
       MOV reg_dac_current, reg_dac_buf0         // DAC: reg_dac_current is current pointer
-      LSL reg_adc_current, reg_frame_total, 5   // 16 * 2 * bufsize
-      ADD reg_adc_current, reg_adc_current, reg_dac_current // ADC: starts 16 * 2 * bufsize beyond DAC
+      LMBD r2, reg_num_channels, 1		// 1, 2 or 3 for 2, 4 or 8 channels
+      LSL reg_adc_current, reg_frame_total, r2
+      LSL reg_adc_current, reg_adc_current, 2   // N * 2 * 2 * bufsize
+      ADD reg_adc_current, reg_adc_current, reg_dac_current // ADC: starts N * 2 * 2 * bufsize beyond DAC
       MOV reg_mcasp_dac_current, reg_mcasp_buf0 // McASP: set current DAC pointer
-      LSL reg_mcasp_adc_current, reg_frame_total, 4 // McASP ADC: starts 4*2*2*bufsize beyond DAC
+      LSL reg_mcasp_adc_current, reg_frame_total, r2 // McASP ADC: starts (N/2)*2*2*bufsize beyond DAC
+      LSL reg_mcasp_adc_current, reg_mcasp_adc_current, 1
       ADC reg_mcasp_adc_current, reg_mcasp_adc_current, reg_mcasp_dac_current
       MOV reg_frame_current, 0
 	
 WRITE_LOOP:
-      // Write 8 channels to DAC from successive values in memory
-      // At the same time, read 8 channels from ADC
+      // Write N channels to DAC from successive values in memory
+      // At the same time, read N channels from ADC
       // Unrolled by a factor of 2 to get high and low words
       MOV r1, 0
 ADC_DAC_LOOP:
@@ -544,7 +568,8 @@
 
       // On even iterations, load two more samples and choose the first one
       // On odd iterations, transmit the second of the samples already loaded
-      QBBS MCASP_DAC_HIGH_WORD, r1, 1
+      // QBBS MCASP_DAC_HIGH_WORD, r1, 1
+      QBBS MCASP_DAC_HIGH_WORD, reg_flags, FLAG_BIT_MCASP_HWORD
 MCASP_DAC_LOW_WORD:	
       // Load next 2 Audio DAC samples and store zero in their place
       LBCO reg_mcasp_dac_data, C_MCASP_MEM, reg_mcasp_dac_current, 4
@@ -561,8 +586,7 @@
       // Take the high word of the previously loaded data
       LSR r7, reg_mcasp_dac_data, 16
 	
-      // Two audio frames per SPI frame = 4 audio samples per SPI frame
-      // Therefore every 2 channels we send one audio sample; this loop already
+      // Every 2 channels we send one audio sample; this loop already
       // sends exactly two SPI channels.
       // Wait for McASP XSTAT[XDATA] to set indicating we can write more data
 MCASP_WAIT_XSTAT:
@@ -573,7 +597,8 @@
 	
       // Same idea with ADC: even iterations, load the sample into the low word, odd
       // iterations, load the sample into the high word and store
-      QBBS MCASP_ADC_HIGH_WORD, r1, 1
+      // QBBS MCASP_ADC_HIGH_WORD, r1, 1
+      QBBS MCASP_ADC_HIGH_WORD, reg_flags, FLAG_BIT_MCASP_HWORD
 MCASP_ADC_LOW_WORD:	
       // Start ADC data at 0
       LDI reg_mcasp_adc_data, 0
@@ -618,12 +643,13 @@
 
       // Read ADC channels: result is always 2 commands behind
       // Start by reading channel 2 (result is channel 0) and go
-      // to 10, but masking the channel number to be between 0 and 7
+      // to N+2, but masking the channel number to be between 0 and N-1
       LDI reg_adc_data, 0
+      ADD r8, r1, 2
+      SUB r7, reg_num_channels, 1
+      AND r8, r8, r7
+      LSL r8, r8, AD7699_CHANNEL_OFFSET
       MOV r7, AD7699_CFG_MASK
-      ADD r8, r1, 2
-      AND r8, r8, 7
-      LSL r8, r8, AD7699_CHANNEL_OFFSET
       OR r7, r7, r8
       ADC_WRITE r7, r7
 
@@ -645,11 +671,13 @@
 
       // Read ADC channels: result is always 2 commands behind
       // Start by reading channel 2 (result is channel 0) and go
-      // to 10, but masking the channel number to be between 0 and 7
+      // to N+2, but masking the channel number to be between 0 and N-1
+      LDI reg_adc_data, 0
+      ADD r8, r1, 2
+      SUB r7, reg_num_channels, 1
+      AND r8, r8, r7
+      LSL r8, r8, AD7699_CHANNEL_OFFSET
       MOV r7, AD7699_CFG_MASK
-      ADD r8, r1, 2
-      AND r8, r8, 7
-      LSL r8, r8, AD7699_CHANNEL_OFFSET
       OR r7, r7, r8
       ADC_WRITE r7, r7
 
@@ -661,16 +689,26 @@
       SBCO reg_adc_data, C_ADC_DAC_MEM, reg_adc_current, 4
       ADD reg_adc_current, reg_adc_current, 4
 
-      // Repeat 4 times (2 samples per loop, r1 += 1 already happened)
+      // Toggle the high/low word for McASP control (since we send one word out of
+      // 32 bits for each pair of SPI channels)
+      XOR reg_flags, reg_flags, (1 << FLAG_BIT_MCASP_HWORD)
+	
+      // Repeat 4 times for 8 channels (2 samples per loop, r1 += 1 already happened)
+      // For 4 or 2 channels, repeat 2 or 1 times, according to flags
       ADD r1, r1, 1
-      QBNE ADC_DAC_LOOP, r1, 8
+      QBNE ADC_DAC_LOOP, r1, reg_num_channels
       QBA ADC_DAC_LOOP_DONE
-	
+
 SPI_SKIP_WRITE:
       // We get here only if the SPI ADC and DAC are disabled
       // Just keep the loop going for McASP
+
+      // Toggle the high/low word for McASP control (since we send one word out of
+      // 32 bits for each pair of SPI channels)
+      XOR reg_flags, reg_flags, (1 << FLAG_BIT_MCASP_HWORD)
+
       ADD r1, r1, 2
-      QBNE ADC_DAC_LOOP, r1, 8
+      QBNE ADC_DAC_LOOP, r1, reg_num_channels
 	
 ADC_DAC_LOOP_DONE:	
       // Increment number of frames, see if we have more to write