From f3ecdd6a895f788d37219206b6d5f782d43d8828 Mon Sep 17 00:00:00 2001
From: Michael Gernoth <michael@gernoth.net>
Date: Tue, 8 Jun 2010 11:22:58 +0200
Subject: [PATCH] use CLEAR instead of usb_reset to recover from errors

---
 usbtmc.c | 41 +++++++++++++++++++++++++++++++++++++++--
 1 file changed, 39 insertions(+), 2 deletions(-)

diff --git a/usbtmc.c b/usbtmc.c
index 2ccbf89..ffebcbf 100644
--- a/usbtmc.c
+++ b/usbtmc.c
@@ -7,7 +7,7 @@
 #include "scope.h"
 #include "usbtmc.h"
 
-#define USB_TIMEOUT 50000
+#define USB_TIMEOUT 10000
 
 #if BYTE_ORDER == LITTLE_ENDIAN
 #define LE32(x) x
@@ -18,7 +18,7 @@
 #endif
 
 /* TODO: fix memory leak here: */
-#define USB_ERROR(s, x) do { if (x < 0) { fprintf(stderr, "usb %s: %s\n", s, usb_strerror()); usb_reset(sc->usb.dev); return 0; } } while(0)
+#define USB_ERROR(s, x) do { if (x < 0) { fprintf(stderr, "usb %s: %s\n", s, usb_strerror()); usbtmc_clear(sc); return 0; } } while(0)
 
 /* This routine locates a scope by VID/PID and returns a struct scope* for it */
 static struct scope* usbtmc_find_scope() {
@@ -133,6 +133,43 @@ static struct usbtmc_capabilities* usbtmc_get_capabilities(struct scope *sc)
 	return &res;
 }
 
+static void usbtmc_clear(struct scope *sc)
+{
+	int r;
+	unsigned char status[2];
+
+	printf("Initiating clear...\n");
+	r = usb_control_msg(sc->usb.dev, 0xA1,
+		USBTMC_CTL_INITIATE_CLEAR,
+		0, 0, (char*)status, 1,
+		USB_TIMEOUT);
+	
+	if ((r != 1) || status[0] != 0x01) {
+		printf("INITIATE_CLEAR failed: %s\n", usb_strerror());
+		return;
+	}
+
+	while(1) {
+		usleep(100000);
+		printf("Waiting for clear to complete...\n");
+
+		r = usb_control_msg(sc->usb.dev, 0xA1,
+			USBTMC_CTL_CHECK_CLEAR_STAT,
+			0, 0, (char*)status, 2,
+			USB_TIMEOUT);
+
+		if ((r != 2) || status[0] != 0x01) {
+			printf("CHECK_CLEAR failed: %s\n", usb_strerror());
+			return;
+		}
+
+		if (status[1] & (1<<0)) {
+			printf("Success!\n");
+			break;
+		}
+	}
+}
+
 /*
  * Send a scpi-command to the scope. The response goes into the buffer
  * called resp, with a size of resplen. If resp==NULL, no response
-- 
2.39.2