blob: efba70ffb6aa058d948556944c732cbaad358800 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
|
#### Printer to CDC
This example demonstrates a USB composite device with a Printer class interface and a CDC serial interface. Data flows bidirectionally between the two:
- Data sent to the Printer (from host) is forwarded to the CDC serial port
- Data sent to the CDC serial port (from host) is forwarded to the Printer IN endpoint
This is useful for debugging printer class communication or as a reference for implementing printer class devices.
#### USB Descriptors
| Interface | Class | Description |
|-----------|-------|-------------|
| 0 | CDC ACM | Virtual serial port |
| 2 | Printer | USB Printer (bidirectional, protocol 2) |
#### Configuration
Notable `tusb_config.h` settings:
```c
#define CFG_TUD_CDC 1
#define CFG_TUD_PRINTER 1
#define CFG_TUD_CDC_RX_BUFSIZE (TUD_OPT_HIGH_SPEED ? 512 : 64)
#define CFG_TUD_CDC_TX_BUFSIZE (TUD_OPT_HIGH_SPEED ? 512 : 64)
#define CFG_TUD_PRINTER_RX_BUFSIZE (TUD_OPT_HIGH_SPEED ? 512 : 64)
#define CFG_TUD_PRINTER_TX_BUFSIZE (TUD_OPT_HIGH_SPEED ? 512 : 64)
```
#### How to Test
The device exposes two endpoints on the host:
- `/dev/ttyACM0` (CDC serial port)
- `/dev/usb/lp0` (USB printer)
Note: the actual device numbers may vary depending on your system.
**Prerequisites (Linux):**
```bash
# Load the USB printer kernel module if not already loaded
sudo modprobe usblp
# Check devices exist
ls /dev/ttyACM* /dev/usb/lp*
```
**Test Printer to CDC (host writes to printer, reads from CDC):**
```bash
# Terminal 1: read from CDC
cat /dev/ttyACM0
# Terminal 2: write to printer
echo "hello from printer" > /dev/usb/lp0
# "hello from printer" appears in Terminal 1
```
**Test CDC to Printer (host writes to CDC, reads from printer):**
```bash
# Terminal 1: read from printer IN endpoint
cat /dev/usb/lp0
# Terminal 2: write to CDC
echo "hello from cdc" > /dev/ttyACM0
# "hello from cdc" appears in Terminal 1
```
**Interactive bidirectional test:**
```bash
# Terminal 1: open CDC serial port
minicom -D /dev/ttyACM0
# Terminal 2: send to printer
echo "tinyusb print example" > /dev/usb/lp0
# Text appears in minicom. Type in minicom to send data back through printer TX.
```
#### IEEE 1284 Device ID
The device responds to GET_DEVICE_ID requests with:
```
MFG:TinyUSB;MDL:Printer to CDC;CMD:PS;CLS:PRINTER;
```
Verify with:
```bash
cat /sys/class/usbmisc/lp0/device/ieee1284_id
```
|
