Feature: transmit_byte for transmitting a single byte

Feature: `all_on` and `all_off` commands for testing
Optimization: marked functions inline
Optimization: inline function for transmitting a single bit

PT6302.c

@@ -34,6 +34,30 @@ inline void PT6302_startup (void)
   _delay_us (TWRSTB);
 }
 
+inline void transmit_bit(const uint8_t data)
+{
+  PORTB &= ~CLKBpin;
+  if ((data & 0x01) == 0)
+    PORTB &= ~DINpin;
+  else
+    PORTB |= DINpin;
+  _delay_us (TCW);
+  PORTB |= CLKBpin;
+  _delay_us (TCW);
+}
+
+void transmit_byte (uint8_t data)
+{
+  _delay_us (1);
+  PORTB &= ~CSBpin;
+  for (int j = 0; j < 8; ++j, data = (data >> 1))
+    {
+      transmit_bit (data);
+    }
+  _delay_us (TCSH);
+  PORTB |= CSBpin;
+}
+
 void transmit_bytes (const uint8_t *payload, const uint8_t size)
 {
   _delay_us (1);
@@ -43,14 +67,7 @@ void transmit_bytes (const uint8_t *payload, const uint8_t size)
       uint8_t data = payload[i];
       for (int j = 0; j < 8; ++j, data = (data >> 1))
         {
-          PORTB &= ~CLKBpin;
-          if ((data & 0x01) == 0)
-            PORTB &= ~DINpin;
-          else
-            PORTB |= DINpin;
-          _delay_us (TCW);
-          PORTB |= CLKBpin;
-          _delay_us (TCW);
+          transmit_bit (data);
         }
       _delay_us (TDOFF);
     }
@@ -65,7 +82,7 @@ void set_ports (uint8_t gp1, uint8_t gp2)
     command |= 0x01;
   if (gp2 != 0)
     command |= 0x02;
-  transmit_bytes (&command, 1);
+  transmit_byte (command);
 }
 
 void set_duty (uint8_t brightness)
@@ -75,7 +92,7 @@ void set_duty (uint8_t brightness)
       brightness = 7;
     }
   const uint8_t command = 0x50 | brightness;
-  transmit_bytes (&command, 1);
+  transmit_byte (command);
 }
 
 void set_digits (uint8_t digit_count)
@@ -86,7 +103,7 @@ void set_digits (uint8_t digit_count)
     digit_count = 9;
   digit_count -= 8;
   const uint8_t command = 0x60 | digit_count;
-  transmit_bytes (&command, 1);
+  transmit_byte (command);
 }
 
 void set_ADRAM (const uint8_t address, const uint8_t *data, uint8_t size)
@@ -119,7 +136,6 @@ void set_CGRAM (const uint8_t address, const uint8_t *data, uint8_t size)
     }
   transmit_bytes (payload, size);
 }
-
 void set_DCRAM (const uint8_t address, const uint8_t *cg_address, uint8_t size)
 {
   if (address > DISPLAY_DIGITS)
@@ -133,4 +149,15 @@ void set_DCRAM (const uint8_t address, const uint8_t *cg_address, uint8_t size)
       payload[i] = cg_address[i - 1];
     }
   transmit_bytes (payload, size);
-}
+}
+void all_on (void)
+{
+  const uint8_t command = 0x72;
+  transmit_byte (command);
+}
+
+void all_off (void)
+{
+  const uint8_t command = 0x71;
+  transmit_byte (command);
+}

PT6302.h

@@ -1,3 +1,4 @@
+#pragma once
 /*
  * AT-VFD
  * Copyright (C) 2022  László Párkányi
@@ -18,15 +19,13 @@
  * USA
  */
 
-#ifndef _PT6302_H_
-#define _PT6302_H_
-
 #define DISPLAY_DIGITS 12
 
 /* PT6302 timing constants, all in usec */
 static const uint8_t TCW = 1;     //CLKB pulse width
 static const uint8_t TDOFF = 16;  //Data processing time
 static const uint8_t DTCSH = 16;  //time difference between tDOFF and tCSH
+static const uint8_t TCSH = 32;   //Chip select hold time
 static const uint8_t TPRZ = 100;  //VDD rise time
 static const uint8_t TWRSTB = 1;  //RSTB pulse width
 
@@ -49,6 +48,19 @@ enum RAM_types{
  * ------------------------------------------------------------- */
 void PT6302_startup (void);
 
+/* --------------------------------
+ * Transmits the LSB of data
+ * Handles communication except CSB
+ * --------------------------------- */
+static inline void transmit_bit(uint8_t data);
+
+/* ------------------------------------------------
+ * Transmits one character (data)
+ * Handles the entire communication
+ * this is (mostly) intended to be used by wrappers
+ * ------------------------------------------------ */
+void transmit_byte(uint8_t data);
+
 /* -------------------------------------------------------------------------------
  * Transmits size byte of data through the VFD controller's interface from payload
  * Handles CLKB, CSB and timing constraints
@@ -59,14 +71,14 @@ void transmit_bytes (const uint8_t *payload, uint8_t size);
  * Sets GP1 and GP2 to the values given in the function call
  * Handles the entire communication
  * --------------------------------------------------------- */
-void set_ports (uint8_t gp1, uint8_t gp2);
+inline void set_ports (uint8_t gp1, uint8_t gp2);
 
 /* ---------------------------------------------------------------------------------------
  * Sets the number of digit_count the VFD has
  * digit_count below 9 are interpreted as 9 and digit_count above 16 are interpreted as 16
  * Handles the entire communication
  * --------------------------------------------------------------------------------------- */
-void set_digits(uint8_t digit_count);
+inline void set_digits(uint8_t digit_count);
 
 /* -----------------------------------------------------------
  * Sets duty cycle of controlled VFD
@@ -74,7 +86,7 @@ void set_digits(uint8_t digit_count);
  * duty = (brightness + 8)/16 (valid between 8/16 and 15/16)
  * Handles the entire communication
  * ----------------------------------------------------------- */
-void set_duty (uint8_t brightness);
+inline void set_duty (uint8_t brightness);
 
 /* ------------------------------------------------------------------------------------------
  * Set the content of the DCRAM - this will display a character from the CGROM/RAM at address
@@ -108,4 +120,15 @@ void set_CGRAM (uint8_t address, const uint8_t *data, uint8_t size);
  * --------------------------------------------------------------------------------------- */
 void set_ADRAM(uint8_t address, const uint8_t* data, uint8_t size);
 
-#endif //_PT6302_H_
+/* -----------------------------------------
+ * Turn all outputs of the VFD controller on
+ * This is primarily used for testing
+ * Handles the entire communication
+ * ----------------------------------------- */
+inline void all_on(void);
+
+/* ------------------------------------------
+ * Turn all outputs of the VFD controller off
+ * Handles the entire communication
+ * ------------------------------------------ */
+inline void all_off(void);

main.c

@@ -25,10 +25,6 @@
 #include <util/delay.h>
 #include "PT6302.h"
 
-/* PT6302 commands */
-static const uint8_t lighton = 0x72;
-static const uint8_t lightoff = 0x71;
-
 
 int main ()
 {
@@ -46,9 +42,9 @@ int main ()
   set_DCRAM (0, characters, DISPLAY_DIGITS);
   while (1)
     {
-      transmit_bytes (&lighton, 1);
+      all_on();
       _delay_us (1000);
-      transmit_bytes (&lightoff, 1);
+      all_off();
       _delay_us (1000);
     }
 }