Status thermal printer with libusb on linux ARM - c++

Question

I known there is a lot of question about status printer ...
i have a Citizen CT-S310 II, i have managed all the code for write character in USB without problem with libusb_bulk_transfer (Text, Bold, Center, CR, CUT_PAPER etc) :
#define ENDPOINT_OUT 0x02
#define ENDPOINT_IN 0x81
struct libusb_device_handle *_handle;
[detach kernel driver...]
[claim interface...]
[etc ...]
r = libusb_bulk_transfer(device_handle, ENDPOINT_OUT, Mydata, out_len, &transferred, 1000);
Now, i need to receive data from the printer to ckeck the status, my first idea was to send the POS command with the same "bulk_transfer" of the doc :
1D (hexa) 72 (hexa) n
n => 1 (Send the papel sensor status)
and retrieve the value by "bulk_transfer" with the end point "ENDPOINT_IN" the doc say there is 8 bytes to receive :
bit 0,1 => paper found by paper near-end sensor 00H
bit 0,1 => paper not found by paper near-end sensor 03H
bit 1,2 => paper found by paper-end sensor 00H
bit 1,2 => paper not found by paper-end sensor 0CH
[...]
so two "bulk_transfer", one for send command status (ENDPOINT_OUT) and one for receive the result (ENDPOINT_IN), but i have allways an USB ERROR ("bulk_transfer" in read = -1)
Maybe the USB don't work like this ? So my second idea was to use the implemented function in PrinterClass USB with the command "control_transfer" :
int r = 0;
int out_len = 1;
unsigned char* _udata = NULL;
uint8_t bmRequestType = LIBUSB_ENDPOINT_IN | LIBUSB_REQUEST_TYPE_CLASS | LIBUSB_RECIPIENT_INTERFACE;
uint8_t bRequest = LIBUSB_REQUEST_GET_STATUS;
uint16_t wValue = 0; // the value field for the setup packet (?????)
uint16_t wIndex = 0; // N° interface printer (the index field for the setup packet)
r = libusb_control_transfer(device_handle, bmRequestType,bRequest,wValue, wIndex,_udata,out_len, USB_TIMEOUT);
i don't exactly how to fill all the parameter, i know it depend of my device, but the doc of libsub is not very explicit.
What is exactly "wValue" ?
What is exactly "wIndex" ? the interface number ??
the parameter LIBUSB_ENDPOINT_IN by default is 0x80, but my printer use 0x81, i must to change this default endpoint ?
Bus 001 Device 004: ID 1d90:2060
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 64
idVendor 0x1d90
idProduct 0x2060
bcdDevice 0.02
iManufacturer 1 CITIZEN
iProduct 2 Thermal Printer
iSerial 3 00000000
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 32
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 0
bmAttributes 0xc0
Self Powered
MaxPower 0mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 2
bInterfaceClass 7 Printer
bInterfaceSubClass 1 Printer
bInterfaceProtocol 2 Bidirectional
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x02 EP 2 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 0
Device Status: 0x0001
Self Powered
The response of "control_transfer" in my case is always 0 :( with paper or without.How send a good "control_transfer" for request the status of my printer ??
All the help for solve my problem is welcome !!!

Answer 1

finally resolved !
The value of LIBUSB_REQUEST_GET_STATUS is 0x00, but for a printer the request status is 0x01.
for check the status of printer with libusb-1.0 :
uint8_t bmRequestType = LIBUSB_ENDPOINT_IN | LIBUSB_REQUEST_TYPE_CLASS | LIBUSB_RECIPIENT_INTERFACE;
uint8_t bRequest = 0x01; // Here not LIBUSB_REQUEST_GET_STATUS
uint16_t wValue = 0;
uint16_t wIndex = 0;
r = libusb_control_transfer(device_handle, bmRequestType,bRequest,wValue, wIndex,&_udata,out_len, USB_TIMEOUT);