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Use feature report to tare scale #37

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Use feature report to tare scale #37

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21 changes: 11 additions & 10 deletions usbscale.c
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Original file line number Diff line number Diff line change
Expand Up @@ -254,20 +254,21 @@ int main(int argc, char **argv)
int scale_result = -1;

// lowest bit is Enforced Zero Return, second bit is Zero Scale
unsigned char tare_report[] = {0x02, 0x02};

// Send zero command via HID feature report 0x02 with a single byte 0x03.
if (arguments.tare) {
r = libusb_interrupt_transfer(
unsigned char tare_report[] = {0x03};
r = libusb_control_transfer(
handle,
LIBUSB_ENDPOINT_OUT + 2, // direction=host to device, type=standard, recipient=device
LIBUSB_ENDPOINT_OUT | LIBUSB_REQUEST_TYPE_CLASS | LIBUSB_RECIPIENT_INTERFACE,
0x09, // HID Set_Report
(3 << 8) | 0x02, // Feature report ID 0x02
0, // interface
tare_report,
CONTROL_REPORT_SIZE,
&len,
10000
);
sizeof(tare_report),
1000);

if (r != 0) {
fprintf(stderr, "errno=%s r=%d (%s) transferred %d bytes\n", strerror(errno), r, libusb_error_name(r), len);
if (r < 0) {
fprintf(stderr, "zero command failed: errno=%s r=%d (%s)\n", strerror(errno), r, libusb_error_name(r));
} else {
fprintf(stderr, "tared\n");
}
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