Implemented SPI batched write for slight performance improvement

Author: chrisws

include/javaproxy.h

@@ -16,8 +16,7 @@ JNIEnv *g_env;
 JavaVM *g_jvm;
 jobject g_activity;
 
-// TWI limit is 255, SPI limit is 64
-#define ARRAY_SIZE 255
+#define ARRAY_SIZE 254
 
 #if defined(ANDROID_MODULE)
   #define attachCurrentThread() g_jvm->AttachCurrentThread(&g_env, nullptr)

ioio/ioio/src/main/java/ioio/smallbasic/SpiMasterImpl.java

@@ -1,15 +1,16 @@
 package ioio.smallbasic;
 
-import java.io.IOException;
-import java.util.Arrays;
-
 import ioio.lib.api.IOIO;
 import ioio.lib.api.SpiMaster;
 import ioio.lib.api.exception.ConnectionLostException;
 import ioio.lib.spi.Log;
 
+import java.io.IOException;
+
 public class SpiMasterImpl extends IOTask {
   private static final String TAG = "SpiMasterImpl";
+  private static final int SPI_WRITE_MAX = 63;
+  private final byte[] BATCH = new byte[SPI_WRITE_MAX];
   private final IOLock<SpiMaster> lock = new IOLock<>();
   private SpiMaster spiMaster = null;
   private int miso;
@@ -56,7 +57,17 @@ public long readWrite(int readLen, final byte[] write, int writeLen) {
   public void write(final byte[] write, int writeLen) {
     handleError();
     lock.invoke((i) -> {
-      spiMaster.writeRead(write, writeLen, writeLen, null, 0);
+      if (writeLen < SPI_WRITE_MAX) {
+        spiMaster.writeRead(write, writeLen, writeLen, null, 0);
+      } else {
+        int srcPos = 0;
+        while (srcPos < writeLen) {
+          int batchLen = Math.min(writeLen - srcPos, SPI_WRITE_MAX);
+          System.arraycopy(write, srcPos, BATCH, 0, batchLen);
+          spiMaster.writeRead(BATCH, batchLen, batchLen, null, 0);
+          srcPos += SPI_WRITE_MAX;
+        }
+      }
     });
   }
 

ioio/main.cpp

@@ -25,6 +25,8 @@
 #define CLASS_SPIMASTER "ioio/smallbasic/SpiMasterImpl"
 #define CLASS_IOIO "ioio/smallbasic/IOIOImpl"
 #define CLASS_IOTASK_ID 1
+#define SPI_WRITE_MAX 63
+#define TWI_WRITE_MAX ARRAY_SIZE
 
 struct IOTask : JavaProxy {
   IOTask() : JavaProxy() {
@@ -46,8 +48,8 @@ struct IOTask : JavaProxy {
   int invokeSpiReadWrite(int argc, slib_par_t *arg, var_s *retval) {
     int result = 0;
     int writeLen = populateByteArray(argc, arg, 1);
-    if (writeLen > ARRAY_SIZE) {
-      error(retval, "write array", 1, ARRAY_SIZE);
+    if (writeLen > SPI_WRITE_MAX) {
+      error(retval, "write array", 1, SPI_WRITE_MAX);
     } else if (_instance != nullptr) {
       attachCurrentThread();
       jmethodID method = g_env->GetMethodID(_clazz, "readWrite", "(I[BI)J");
@@ -89,8 +91,8 @@ struct IOTask : JavaProxy {
   int invokeTwiReadWrite(int argc, slib_par_t *arg, var_s *retval) {
     int result = 0;
     int writeLen = populateByteArray(argc, arg, 2);
-    if (writeLen > ARRAY_SIZE) {
-      error(retval, "write array", 1, ARRAY_SIZE);
+    if (writeLen > TWI_WRITE_MAX) {
+      error(retval, "write array", 1, TWI_WRITE_MAX);
     } else if (_instance != nullptr) {
       attachCurrentThread();
       jmethodID method = g_env->GetMethodID(_clazz, "readWrite", "(II[BI)J");
@@ -113,8 +115,8 @@ struct IOTask : JavaProxy {
   int invokeTwiWrite(int argc, slib_par_t *arg, var_s *retval) {
     int result = 0;
     int writeLen = populateByteArray(argc, arg, 1);
-    if (writeLen > ARRAY_SIZE) {
-      error(retval, "write array", 1, ARRAY_SIZE);
+    if (writeLen > TWI_WRITE_MAX) {
+      error(retval, "write array", 1, TWI_WRITE_MAX);
     } else if (_instance != nullptr) {
       attachCurrentThread();
       jmethodID method = g_env->GetMethodID(_clazz, "write", "(I[BI)V");

ioio/samples/st7735s.bas

@@ -16,6 +16,7 @@ rem
 import ioio
 
 const ST7735_SLPOUT 0x11
+const ST7735_DISPOFF 0x28
 const ST7735_DISPON 0x29
 const ST7735_CASET 0x2A
 const ST7735_RASET 0x2B
@@ -82,7 +83,7 @@ sub resetDisplay()
   rstOut.write(0)
   delay 50
   rstOut.write(1)
-  delay 50
+  delay 150
 end
 
 sub initST7735S()
@@ -133,16 +134,18 @@ end
 rem Fill display with a given RGB value
 sub fill_LCD(r, g, b)
   local i, _data
-  Set_LCD_for_write_at_X_Y(0, 0)
+  ' higher values didn't improve performance
+  local bufSize = 40
 
-  for i = 1 to 21
+  for i = 1 to bufSize
     _data << b
     _data << g
     _data << r
   next
 
+  Set_LCD_for_write_at_X_Y(0, 0)
   rsOut.write(1)
-  for i = 0 to (128 * 128) / 21
+  for i = 0 to (128 * 128) / bufSize
     spi.write(_data)
   next i
 end
@@ -154,4 +157,8 @@ sub put_Pixel(x, y, r, g, b)
 end
 
 initST7735S()
-fill_LCD(1, 212, 31)
+randomize
+t1 = timer
+fill_LCD(rnd*255, rnd*255, rnd*255)
+print format("Elap: ###", timer-t1)
+delay 5000