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@ -60,6 +60,12 @@ static libusb_device* find_scale(libusb_device**);
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// program should read again (i.e. continue looping).
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//
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static int print_scale_data(unsigned char*);
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//
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// take device and fetch bEndpointAddress for the first endpoint
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//
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uint8_t get_first_endpoint_address(libusb_device* dev);
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//
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// **UNITS** is an array of all the unit abbreviations as set forth by *HID
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// Point of Sale Usage Tables*, version 1.02, by the USB Implementers' Forum.
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@ -197,8 +203,7 @@ int main(void)
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handle,
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//bmRequestType => direction: in, type: class,
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// recipient: interface
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LIBUSB_ENDPOINT_IN | //LIBUSB_REQUEST_TYPE_CLASS |
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LIBUSB_RECIPIENT_INTERFACE,
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get_first_endpoint_address(dev),
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data,
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WEIGH_REPORT_SIZE, // length of data
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&len,
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@ -276,16 +281,12 @@ static int print_scale_data(unsigned char* dat) {
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uint8_t report = dat[0];
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uint8_t status = dat[1];
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uint8_t unit = dat[2];
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uint8_t expt = dat[3];
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double weight = (double)(dat[4] + (dat[5] << 8)) / 10;
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if(expt != 255 && expt != 0) {
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if (expt > 127) {
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weight = weight * pow(10, expt-255);
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} else {
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weight = pow(weight, expt);
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}
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}
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// Accoring to the docs, scaling applied to the data as a base ten exponent
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int8_t expt = dat[3];
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// convert to machine order at all times
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double weight = (double) le16toh(dat[5] << 8 | dat[4]);
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// since the expt is signed, we do not need no trickery
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weight = weight * pow(10, expt);
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//
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// The scale's first byte, its "report", is always 3.
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@ -418,3 +419,22 @@ static libusb_device* find_scale(libusb_device **devs)
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return NULL;
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}
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uint8_t get_first_endpoint_address(libusb_device* dev)
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{
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// default value
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uint8_t endpoint_address = LIBUSB_ENDPOINT_IN | LIBUSB_RECIPIENT_INTERFACE; //| LIBUSB_RECIPIENT_ENDPOINT;
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struct libusb_config_descriptor *config;
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int r = libusb_get_config_descriptor(dev, 0, &config);
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if (r == 0) {
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// assuming we have only one endpoint
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endpoint_address = config->interface[0].altsetting[0].endpoint[0].bEndpointAddress;
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libusb_free_config_descriptor(config);
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}
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#ifdef DEBUG
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printf("bEndpointAddress 0x%02x\n", endpoint_address);
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#endif
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return endpoint_address;
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}
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