diff --git a/Marlin/src/HAL/HAL_AVR/HAL_spi_AVR.cpp b/Marlin/src/HAL/HAL_AVR/HAL_spi_AVR.cpp
index 31d2f25b42..a3fe161251 100644
--- a/Marlin/src/HAL/HAL_AVR/HAL_spi_AVR.cpp
+++ b/Marlin/src/HAL/HAL_AVR/HAL_spi_AVR.cpp
@@ -27,8 +27,6 @@
 
 /**
  * Description: HAL for AVR - SPI functions
- *
- * For __AVR__
  */
 
 #ifdef __AVR__
@@ -68,10 +66,12 @@ void spiBegin (void) {
 }
 
 
-//------------------------------------------------------------------------------
 #if DISABLED(SOFTWARE_SPI)
-  // functions for hardware SPI
+
   //------------------------------------------------------------------------------
+  // Hardware SPI
+  //------------------------------------------------------------------------------
+
   // make sure SPCR rate is in expected bits
   #if (SPR0 != 0 || SPR1 != 1)
     #error "unexpected SPCR bits"
@@ -95,14 +95,13 @@ void spiBegin (void) {
     SPSR = spiRate & 1 || spiRate == 6 ? 0 : _BV(SPI2X);
   }
 
-  //------------------------------------------------------------------------------
   /** SPI receive a byte */
   uint8_t spiRec(void) {
     SPDR = 0xFF;
     while (!TEST(SPSR, SPIF)) { /* Intentionally left empty */ }
     return SPDR;
   }
-  //------------------------------------------------------------------------------
+
   /** SPI read data  */
   void spiRead(uint8_t* buf, uint16_t nbyte) {
     if (nbyte-- == 0) return;
@@ -115,13 +114,13 @@ void spiBegin (void) {
     while (!TEST(SPSR, SPIF)) { /* Intentionally left empty */ }
     buf[nbyte] = SPDR;
   }
-  //------------------------------------------------------------------------------
+
   /** SPI send a byte */
   void spiSend(uint8_t b) {
     SPDR = b;
     while (!TEST(SPSR, SPIF)) { /* Intentionally left empty */ }
   }
-  //------------------------------------------------------------------------------
+
   /** SPI send block  */
   void spiSendBlock(uint8_t token, const uint8_t* buf) {
     SPDR = token;
@@ -191,25 +190,21 @@ void spiBegin (void) {
   }
 
 
-       //------------------------------------------------------------------------------
-#else  // SOFTWARE_SPI
-       //------------------------------------------------------------------------------
+#else
+
   /** nop to tune soft SPI timing */
   #define nop asm volatile ("\tnop\n")
 
   /** Set SPI rate */
   void spiInit(uint8_t spiRate) {
-    // nothing to do
-    UNUSED(spiRate);
+    UNUSED(spiRate);  // nothing to do
   }
 
   /** Begin SPI transaction, set clock, bit order, data mode */
   void spiBeginTransaction(uint32_t spiClock, uint8_t bitOrder, uint8_t dataMode) {
-    // nothing to do
-    UNUSED(spiBeginTransaction);
+    UNUSED(spiBeginTransaction);  // nothing to do
   }
 
-  //------------------------------------------------------------------------------
   /** Soft SPI receive byte */
   uint8_t spiRec() {
     uint8_t data = 0;
@@ -221,8 +216,7 @@ void spiBegin (void) {
     for (uint8_t i = 0; i < 8; i++) {
       WRITE(SCK_PIN, HIGH);
 
-      // adjust so SCK is nice
-      nop;
+      nop; // adjust so SCK is nice
       nop;
 
       data <<= 1;
@@ -231,48 +225,45 @@ void spiBegin (void) {
 
       WRITE(SCK_PIN, LOW);
     }
-    // enable interrupts
+
     sei();
     return data;
   }
-  //------------------------------------------------------------------------------
+
   /** Soft SPI read data */
   void spiRead(uint8_t* buf, uint16_t nbyte) {
     for (uint16_t i = 0; i < nbyte; i++)
       buf[i] = spiRec();
   }
-  //------------------------------------------------------------------------------
+
   /** Soft SPI send byte */
   void spiSend(uint8_t data) {
     // no interrupts during byte send - about 8µs
     cli();
     for (uint8_t i = 0; i < 8; i++) {
       WRITE(SCK_PIN, LOW);
-
       WRITE(MOSI_PIN, data & 0x80);
-
       data <<= 1;
-
       WRITE(SCK_PIN, HIGH);
     }
-    // hold SCK high for a few ns
-    nop;
+
+    nop; // hold SCK high for a few ns
     nop;
     nop;
     nop;
 
     WRITE(SCK_PIN, LOW);
-    // enable interrupts
+
     sei();
   }
-  //------------------------------------------------------------------------------
+
   /** Soft SPI send block */
   void spiSendBlock(uint8_t token, const uint8_t* buf) {
     spiSend(token);
     for (uint16_t i = 0; i < 512; i++)
       spiSend(buf[i]);
   }
-#endif  // SOFTWARE_SPI
 
+#endif // SOFTWARE_SPI
 
 #endif // __AVR__
diff --git a/Marlin/src/HAL/HAL_DUE/HAL_spi_Due.cpp b/Marlin/src/HAL/HAL_DUE/HAL_spi_Due.cpp
index c866ae9d7b..a1934886f9 100644
--- a/Marlin/src/HAL/HAL_DUE/HAL_spi_Due.cpp
+++ b/Marlin/src/HAL/HAL_DUE/HAL_spi_Due.cpp
@@ -656,8 +656,8 @@
 
     // Read from SPI into buffer
     void spiRead(uint8_t* buf, uint16_t nbyte) {
-      if (nbyte-- == 0) return;
-
+      if (!nbyte) return;
+      --nbyte;
       for (int i = 0; i < nbyte; i++) {
         //WHILE_TX(0);
         SPI0->SPI_TDR = 0x000000FF | SPI_PCS(SPI_CHAN);
@@ -669,7 +669,7 @@
     }
 
     // Write single byte to SPI
-    void spiSend(byte b) {
+    void spiSend(const byte b) {
       // write byte with address and end transmission flag
       SPI0->SPI_TDR = (uint32_t)b | SPI_PCS(SPI_CHAN) | SPI_TDR_LASTXFER;
       WHILE_TX(0);
@@ -678,16 +678,17 @@
       //DELAY_US(1U);
     }
 
-    void spiSend(const uint8_t* buf, size_t n) {
-      if (n == 0) return;
-      for (size_t i = 0; i < n - 1; i++) {
+    void spiSend(const uint8_t* buf, size_t nbyte) {
+      if (!nbyte) return;
+      --nbyte;
+      for (size_t i = 0; i < nbyte; i++) {
         SPI0->SPI_TDR = (uint32_t)buf[i] | SPI_PCS(SPI_CHAN);
         WHILE_TX(0);
         WHILE_RX(0);
         SPI0->SPI_RDR;
         //DELAY_US(1U);
       }
-      spiSend(buf[n - 1]);
+      spiSend(buf[nbyte]);
     }
 
     void spiSend(uint32_t chan, byte b) {
@@ -698,15 +699,16 @@
       FLUSH_RX();
     }
 
-    void spiSend(uint32_t chan, const uint8_t* buf, size_t n) {
-      if (n == 0) return;
-      for (int i = 0; i < (int)n - 1; i++) {
+    void spiSend(uint32_t chan, const uint8_t* buf, size_t nbyte) {
+      if (!nbyte) return;
+      --nbyte;
+      for (size_t i = 0; i < nbyte; i++) {
         WHILE_TX(0);
         SPI0->SPI_TDR = (uint32_t)buf[i] | SPI_PCS(chan);
         WHILE_RX(0);
         FLUSH_RX();
       }
-      spiSend(chan, buf[n - 1]);
+      spiSend(chan, buf[nbyte]);
     }
 
     // Write from buffer to SPI
@@ -775,17 +777,15 @@
     uint8_t spiRec() { return (uint8_t)spiTransfer(0xFF); }
 
     void spiRead(uint8_t* buf, uint16_t nbyte) {
-      if (nbyte)
-        for (int i = 0; i < nbyte; i++)
-          buf[i] = spiTransfer(0xFF);
+      for (int i = 0; i < nbyte; i++)
+        buf[i] = spiTransfer(0xFF);
     }
 
     void spiSend(uint8_t data) { spiTransfer(data); }
 
     void spiSend(const uint8_t* buf, size_t nbyte) {
-      if (nbyte)
-        for (uint16_t i = 0; i < nbyte; i++)
-          spiTransfer(buf[i]);
+      for (uint16_t i = 0; i < nbyte; i++)
+        spiTransfer(buf[i]);
     }
 
     void spiSendBlock(uint8_t token, const uint8_t* buf) {
diff --git a/Marlin/src/HAL/HAL_LPC1768/HAL_spi.cpp b/Marlin/src/HAL/HAL_LPC1768/HAL_spi.cpp
index d2aa329a81..31dc9c4da0 100644
--- a/Marlin/src/HAL/HAL_LPC1768/HAL_spi.cpp
+++ b/Marlin/src/HAL/HAL_LPC1768/HAL_spi.cpp
@@ -81,17 +81,15 @@
   uint8_t spiRec() { return spiTransfer(0xFF); }
 
   void spiRead(uint8_t*buf, uint16_t nbyte) {
-    if (nbyte)
-      for (int i = 0; i < nbyte; i++)
-        buf[i] = spiTransfer(0xFF);
+    for (int i = 0; i < nbyte; i++)
+      buf[i] = spiTransfer(0xFF);
   }
 
   void spiSend(uint8_t b) { (void)spiTransfer(b); }
 
-  void spiSend(const uint8_t* buf, size_t n) {
-    if (n)
-      for (uint16_t i = 0; i < n; i++)
-        (void)spiTransfer(buf[i]);
+  void spiSend(const uint8_t* buf, size_t nbyte) {
+    for (uint16_t i = 0; i < nbyte; i++)
+      (void)spiTransfer(buf[i]);
   }
 
   void spiSendBlock(uint8_t token, const uint8_t* buf) {
@@ -178,15 +176,14 @@
 
   void spiSend(uint8_t b) { doio(b); }
 
-  void spiSend(const uint8_t* buf, size_t n) {
-    if (n)
-      for (uint16_t i = 0; i < n; i++) doio(buf[i]);
+  void spiSend(const uint8_t* buf, size_t nbyte) {
+    for (uint16_t i = 0; i < nbyte; i++) doio(buf[i]);
   }
 
   void spiSend(uint32_t chan, byte b) {
   }
 
-  void spiSend(uint32_t chan, const uint8_t* buf, size_t n) {
+  void spiSend(uint32_t chan, const uint8_t* buf, size_t nbyte) {
   }
 
   // Read single byte from SPI
@@ -195,9 +192,8 @@
   uint8_t spiRec(uint32_t chan) { return 0; }
 
   // Read from SPI into buffer
-  void spiRead(uint8_t*buf, uint16_t nbyte) {
-    if (nbyte)
-      for (int i = 0; i < nbyte; i++) buf[i] = doio(0xff);
+  void spiRead(uint8_t *buf, uint16_t nbyte) {
+    for (uint16_t i = 0; i < nbyte; i++) buf[i] = doio(0xFF);
   }
 
   static uint8_t spiTransfer(uint8_t b) {