[ECOS] Serial port contention

[ECOS] Serial port contention

[David Ho]

Hi,

I am debugging issues with my serial port.  What I need to do is to be
able to share one serial port for diag output and SLIP communication.

As I dig deeper I found out that the serial port is configured to do
blocking reads.  However, an cyg_io_read always returns char '\0' even
when nothing is received.

Has anyone come across this issue?  Is there a good preventive measure
I can use to make sure there is no contention?

Thanks, David

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[ECOS] Re: Serial port contention

[David Ho]

> Has anyone come across this issue?  Is there a good preventive measure
> I can use to make sure there is no contention?

This is what I do when I need to debug my system while my only serial
port is being used.
Stolen from a ppc board, all credits go to the originator(s).

David
---

commit 5b20c814009df6a19e63adc9058be47763e5496e
Author: David Ho <davidho@nanometrics.ca>
Date:   Mon Aug 14 07:52:59 2006 -0400

    Write diagnostics to RAM.

diff --git a/packages/hal/arm/at91/var/current/src/hal_diag.c
b/packages/hal/arm/at91/var/current/src/hal_diag.c
index 73c4830..34a8c3f 100644
--- a/packages/hal/arm/at91/var/current/src/hal_diag.c
+++ b/packages/hal/arm/at91/var/current/src/hal_diag.c
@@ -65,6 +65,49 @@ #include <cyg/hal/hal_diag.h>

 #include <cyg/hal/var_io.h>             // USART registers

+#define CYGDBG_DIAG_BUF
+
+#ifdef CYGDBG_DIAG_BUF
+// Keep diag messages in a buffer for later [re]display
+
+int enable_diag_uart = 0;
+int enable_diag_buf = 1;
+//static char diag_buf[40960*4];
+static char diag_buf[4096*4];
+static int  diag_buf_ptr = 0;
+
+/**
+ * Turn this into a circular buffer - DKWH
+ */
+static void
+diag_putc(char c)
+{
+    if (enable_diag_buf) {
+        diag_buf[diag_buf_ptr++] = c;
+        if (diag_buf_ptr == sizeof(diag_buf)) {
+           diag_buf_ptr--;
+       }
+    }
+}
+
+/**
+ * Restore buffer after buffer dump - DKWH
+ */
+void
+dump_diag_buf(int start, int len)
+{
+    int i;
+    enable_diag_uart = 1;
+    enable_diag_buf = 0;
+    if (len == 0) len = diag_buf_ptr;
+    diag_printf("\nDiag buf\n");
+    for (i = start;  i < len;  i++) {
+        hal_diag_write_char(diag_buf[i]);
+    }
+    enable_diag_buf = 1;
+}
+#endif // CYGDBG_DIAG_BUF
+
 //-----------------------------------------------------------------------------
 typedef struct {
     cyg_uint8* base;
@@ -104,6 +147,12 @@ cyg_hal_plf_serial_putc(void *__ch_data,
 {
     cyg_uint8* base = ((channel_data_t*)__ch_data)->base;
     cyg_uint32 status, ch;
+
+#ifdef CYGDBG_DIAG_BUF
+    diag_putc(c);
+    if (!enable_diag_uart) return;
+#endif // CYGDBG_DIAG_BUF
+
     CYGARC_HAL_SAVE_GP();

     do {

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