Change RST pin to emulate an open drain behavior

phdussud · Nov 7, 2022 · ac7c57c · ac7c57c
1 parent 2d4c959
commit ac7c57c
Show file tree

Hide file tree

Showing 2 changed files with 32 additions and 4 deletions.
diff --git a/pio_jtag.c b/pio_jtag.c
@@ -7,6 +7,32 @@ void jtag_task();//to process USB OUT packets while waiting for DMA to finish
 
 #define DMA
 
+#if 0
+static bool pins_source = false; //false: PIO, true: GPIO
+
+static void switch_pins_source(const pio_jtag_inst_t *jtag, bool gpio)
+{
+    if (pins_source != gpio)
+    {
+        if (gpio)
+        {
+            gpio_put(jtag->pin_tdi, gpio_get(jtag->pin_tdi));
+            gpio_set_function(jtag->pin_tdi, GPIO_FUNC_SIO);
+            gpio_put(jtag->pin_tck, gpio_get(jtag->pin_tck));
+            gpio_set_function(jtag->pin_tck, GPIO_FUNC_SIO);
+            gpio_set_dir_out_masked((1 << jtag->pin_tdi) | (1 << jtag->pin_tck));
+        }
+        else
+        {
+            gpio_set_function(jtag->pin_tdi, GPIO_FUNC_PIO0);
+            gpio_set_function(jtag->pin_tck, GPIO_FUNC_PIO0);
+        }
+        pins_source = gpio;
+    }
+}
+#endif
+
+
 
 #ifdef DMA
 
@@ -215,13 +241,14 @@ uint8_t __time_critical_func(pio_jtag_write_tms_blocking)(const pio_jtag_inst_t
 
 static void init_pins(uint pin_tck, uint pin_tdi, uint pin_tdo, uint pin_tms, uint pin_rst, uint pin_trst)
 {
+    // emulate open drain with pull up and direction
+    gpio_pull_up(pin_rst);
     gpio_clr_mask((1u << pin_tms) | (1u << pin_rst) | (1u << pin_trst));
     gpio_init_mask((1u << pin_tms) | (1u << pin_rst) | (1u << pin_trst));
-    gpio_set_dir_masked( (1u << pin_tms) | (1u << pin_rst) | (1u << pin_trst), 0xffffffffu);
+    gpio_set_dir_masked( (1u << pin_tms) | (1u << pin_trst), 0xffffffffu);
+    gpio_set_dir(pin_rst, false);
 }
 
-
-
 void init_jtag(pio_jtag_inst_t* jtag, uint freq, uint pin_tck, uint pin_tdi, uint pin_tdo, uint pin_tms, uint pin_rst, uint pin_trst)
 {
     init_pins(pin_tck, pin_tdi, pin_tdo, pin_tms, pin_rst, pin_trst);

diff --git a/pio_jtag.h b/pio_jtag.h
@@ -37,7 +37,8 @@ static inline void jtag_set_tms(const pio_jtag_inst_t *jtag, bool value)
 }
 static inline void jtag_set_rst(const pio_jtag_inst_t *jtag, bool value)
 {
-    gpio_put(jtag->pin_rst, value);
+    /* Change the direction to out to drive pin to 0 or to in to emulate open drain */
+    gpio_set_dir(jtag->pin_rst, !value);
 }
 static inline void jtag_set_trst(const pio_jtag_inst_t *jtag, bool value)
 {