Halt FPGA if PROGRAM button held at start-up

Manipulate INITN only at start-up

firmware/src/boards/cynthion_d11/fpga.c

@@ -14,18 +14,8 @@
 
 #include <apollo_board.h>
 
-/**
- * Sets up the I/O pins needed to configure the FPGA.
- */
-void fpga_io_init(void)
-{
-	// By default, keep PROGRAM_N from being driven.
-	gpio_set_pin_level(FPGA_PROGRAM, true);
-	gpio_set_pin_direction(FPGA_PROGRAM, GPIO_DIRECTION_IN);
-}
-
 /*
- * Allows or disallows the FPGA from configuring from flash. When disallowed,
+ * Allows or disallows the FPGA from configuring. When disallowed,
  * initialization (erasing of configuration memory) takes place, but the FPGA
  * does not proceed to the configuration phase.
  */
@@ -45,12 +35,22 @@ void permit_fpga_configuration(bool enable)
 }
 
 /**
- * Requests that the FPGA clear its configuration and try to reconfigure.
+ * Sets up the I/O pins needed to configure the FPGA.
  */
-void trigger_fpga_reconfiguration(void)
+void fpga_io_init(void)
 {
+	// By default, keep PROGRAM_N from being driven.
+	gpio_set_pin_level(FPGA_PROGRAM, true);
+	gpio_set_pin_direction(FPGA_PROGRAM, GPIO_DIRECTION_IN);
+
 	permit_fpga_configuration(true);
+}
 
+/**
+ * Requests that the FPGA clear its configuration and try to reconfigure.
+ */
+void trigger_fpga_reconfiguration(void)
+{
 	gpio_set_pin_direction(FPGA_PROGRAM, GPIO_DIRECTION_OUT);
 	gpio_set_pin_level(FPGA_PROGRAM, false);
 
@@ -65,8 +65,6 @@ void trigger_fpga_reconfiguration(void)
  */
 void force_fpga_offline(void)
 {
-	permit_fpga_configuration(false);
-
 	gpio_set_pin_direction(FPGA_PROGRAM, GPIO_DIRECTION_OUT);
 	gpio_set_pin_level(FPGA_PROGRAM, false);
 }

firmware/src/boards/cynthion_d11/usb_switch.c

@@ -40,7 +40,6 @@ void take_over_usb(void)
 void switch_control_task(void)
 {
 	if (gpio_get_pin_level(PROGRAM_BUTTON) == false) {
-		force_fpga_offline();
 		take_over_usb();
 	}
 }

firmware/src/main.c

@@ -58,10 +58,12 @@ int main(void)
 	// Trigger an FPGA reconfiguration; so the FPGA automatically
 	// configures itself from its SPI ROM on reset. This effectively
 	// makes the RESET button reset both the uC and the FPGA.
-	// Only reconfigure the FPGA if the PROGRAM button is not being
-	// pressed.
         if (gpio_get_pin_level(PROGRAM_BUTTON) == true) {
 		trigger_fpga_reconfiguration();
+	} else {
+		// If PROGRAM button is held down at start-up, halt the FPGA
+		// instead of configuring it.
+		force_fpga_offline();
 	}
 
 	while (1) {