diff --git a/usbscale.c b/usbscale.c
index 9cbabf2..56d6540 100644
--- a/usbscale.c
+++ b/usbscale.c
@@ -29,6 +29,8 @@ along with this program. If not, see .
#include
#include
#include
+#include
+#include
//
// This program uses libusb-1.0 (not the older libusb-0.1) for USB
@@ -47,7 +49,9 @@ along with this program. If not, see .
//
#include "scales.h"
-#define WEIGH_REPORT_SIZE 0x06
+// Define the number of bytes long that each type of report is
+#define WEIGH_REPORT_SIZE 6
+#define CONTROL_REPORT_SIZE 2
//
// **find_scale** takes a libusb device list and finds the first USB device
@@ -92,7 +96,7 @@ const char* UNITS[13] = {
// main
// ----
//
-int main(void)
+int main(int argc, char **argv)
{
libusb_device **devs;
int r; // holds return codes
@@ -171,7 +175,28 @@ int main(void)
*/
unsigned char data[WEIGH_REPORT_SIZE];
int len;
+ len = 0;
int scale_result = -1;
+
+ // lowest bit is Enforced Zero Return, second bit is Zero Scale
+ unsigned char tare_report[] = {0x02, 0x02};
+
+ if (argc > 1 && strncmp(argv[1], "zero", 5) == 0) {
+ r = libusb_interrupt_transfer(
+ handle,
+ LIBUSB_ENDPOINT_OUT + 2, // direction=host to device, type=standard, recipient=device
+ tare_report,
+ CONTROL_REPORT_SIZE,
+ &len,
+ 10000
+ );
+
+ if (r != 0) {
+ fprintf(stderr, "errno=%s r=%d (%s) transferred %d bytes\n", strerror(errno), r, libusb_error_name(r), len);
+ } else {
+ fprintf(stderr, "tared\n");
+ }
+ }
//
// For some reason, we get old data the first time, so let's just get that
@@ -181,8 +206,7 @@ int main(void)
handle,
//bmRequestType => direction: in, type: class,
// recipient: interface
- LIBUSB_ENDPOINT_IN | //LIBUSB_REQUEST_TYPE_CLASS |
- LIBUSB_RECIPIENT_INTERFACE,
+ LIBUSB_ENDPOINT_IN + 1,
data,
WEIGH_REPORT_SIZE, // length of data
&len,