add command flushing and broadcast

lib/led_max7219.c

@@ -155,24 +155,38 @@ static const uint8_t ascii_7segments[] = {
 	0x78, // } ([)  
 	0x01, // ~
 };
+
+/** number of display in the chain */
+uint8_t lex_max7219_displays = 0;
+
 /** write data on SPI bus and handle load signal
  *  @param[in] data bytes to write
  */
 static void led_max7219_write(uint16_t data, uint8_t display)
 {
+	if (lex_max7219_displays<=display && 0xff!=display) { // display no in chain
+		return;
+	}
+
 	gpio_clear(GPIO(LED_MAX7219_LOAD_PORT), GPIO(LED_MAX7219_LOAD_PIN)); // ensure load pin is low (data is put in MAX7219 register on rising edge)
-	for (uint16_t i=0; i<=display; i++) { // go though all displays
+	for (uint8_t i=lex_max7219_displays; i>0; i--) { // go though all displays
 		while (SPI_SR(SPI(LED_MAX7219_SPI))&SPI_SR_BSY); // wait until not busy
-		spi_send(SPI(LED_MAX7219_SPI), data); // send data
+		if (0xff==display || i==(display+1)) { // right display or broadcast message
+			spi_send(SPI(LED_MAX7219_SPI), data); // send data
+		} else {
+			spi_send(SPI(LED_MAX7219_SPI), 0x0000); // send no-op command to shift command to correct display or out
+		}
 		while (!(SPI_SR(SPI(LED_MAX7219_SPI))&SPI_SR_TXE)); // wait until Tx is empty (reference manual says BSY should also cover this, but it doesn't)
 		while (SPI_SR(SPI(LED_MAX7219_SPI))&SPI_SR_BSY); // wait until not busy (= transmission completed)
-		data = 0x0000; // send no-op command to shift initial command to correct display
 	}
 	gpio_set(GPIO(LED_MAX7219_LOAD_PORT), GPIO(LED_MAX7219_LOAD_PIN)); // create rising edge on load pin for data to be set in MAX7219 register
 }
 
-void led_max7219_setup(void)
+void led_max7219_setup(uint8_t displays)
 {
+	// saved number of displays
+	lex_max7219_displays = displays;
+
 	// configure GPIO for load line
 	rcc_periph_clock_enable(RCC_GPIO(LED_MAX7219_LOAD_PORT)); // enable clock for GPIO peripheral
 	gpio_clear(GPIO(LED_MAX7219_LOAD_PORT), GPIO(LED_MAX7219_LOAD_PIN)); // idle low (load on rising edge)

lib/led_max7219.h

@@ -22,30 +22,36 @@
 #pragma once
 
 /** setup communication with MAX7219 IC
+ *  @param[in] displays number of displays in the chain
  */
-void led_max7219_setup(void);
+void led_max7219_setup(uint8_t displays);
+/** do nothing (no operation)
+ *  @param[in] display display number in chain (0xff for all)
+ *  @note send it to the last display in the chain to clear the previous command from the chain
+ */
+void led_max7219_nop(uint8_t display);
 /** switch display on
- *  @param[in] display display number in chain
+ *  @param[in] display display number in chain (0xff for all)
  */
 void led_max7219_on(uint8_t display);
 /** switch display off
- *  @param[in] display display number in chain
+ *  @param[in] display display number in chain (0xff for all)
  */
 void led_max7219_off(uint8_t display);
 /** switch display in test or normal operation mode
  *  @param[in] test switch in test mode (else normal operation)
- *  @param[in] display display number in chain
+ *  @param[in] display display number in chain (0xff for all)
  */
 void led_max7219_test(bool test, uint8_t display);
 /** set display intensity
  *  @param[in] intensity level to set (0-15)
  *  @param[in] digits number of digits to display (1-8)
- *  @param[in] display display number in chain
+ *  @param[in] display display number in chain (0xff for all)
  */
 void led_max7219_intensity(uint8_t intensity, uint8_t digits, uint8_t display);
 /** display text
  *  @param[in] text text to display (8 characters)
- *  @param[in] display display number in chain
+ *  @param[in] display display number in chain (0xff for all)
  *  @note use first bit of each character to enable dot
  *  @return false if string has unsupported characters
  */
@@ -53,6 +59,6 @@ bool led_max7219_text(char* text, uint8_t display);
 /** display number
  *  @param[in] number number to display (8 digits max)
  *  @param[in] dots set bit if dot on corresponding digit should be displayed
- *  @param[in] display display number in chain
+ *  @param[in] display display number in chain (0xff for all)
  */
 void led_max7219_number(uint32_t number, uint8_t dots, uint8_t display);