ENC28J60 is a simple Ethernet controller that can act as an external network card for single-board computers with GPIO (there is even a ready-made driver for the raspberry) and other arduins. GPIOs are not displayed on my laptop, let's try to fix this flaw and screw ENC28J60 to it using STM32F103 and a USB lanyard.
Let's see how you can do this.
We need:
ENC28J60
STM32 USB device (, ):
Linux ( Ubuntu 16)
Ethernet ( raspberry pi), wi-fi ( )
STM32F103 , . ENC28J60 ( c ). ENC28J60 STM32F103 SPI1 .
(usb) -> stm32(SPI) -> ENC28J60(Ethernet ) -> raspberry
, user space. tap ( , Ethernet , tun , ip ), ( tap_handler.c). Linux, tap_handler' tap . , , tap , tap_handler', - . , tap_handler tap , /dev/ttyACM0 ( USB Linux). /dev/ttyACM0, tap .
( vpn). , .
STM32 CubeMX USB CDC (virtual com port). SMT32 Linux /dev/ttyACM0 ( ). , STM32, , STM32.
STM32 . ( CDC_Receive_FS
usbd_cdc_if.c) ENC28J60, , ENC28J60 CDC_Transmit_FS
.
, CDC . , . , ( , wireshark usb). , - - STM32, , .. . .
:
sudo openvpn --mktun --dev tap0
ip :
sudo ifconfig tap0 10.0.0.1/24 up
tap_handler.
/dev/ttyACM0 raw (, .). :
char cdc_name[20]="/dev/ttyACM0";
int tty_fd = open(cdc_name, O_RDWR | O_NOCTTY);
struct termios portSettings;
tcgetattr(tty_fd, &portSettings);
cfmakeraw(&portSettings);
tcsetattr(tty_fd, TCSANOW, &portSettings);
tcflush(tty_fd, TCOFLUSH);
tap_handler tap0:
/* dev tap0*/
int tun_alloc(char *dev, int flags) {
struct ifreq ifr;
int fd, err;
char *clonedev = "/dev/net/tun";
/* /dev/net/tun */
if( (fd = open(clonedev , O_RDWR)) < 0 ) {
perror("Opening /dev/net/tun");
return fd;
}
memset(&ifr, 0, sizeof(ifr));
ifr.ifr_flags = flags;
/* tap0 */
if (*dev) {
strncpy(ifr.ifr_name, dev, IFNAMSIZ);
}
/* */
if( (err = ioctl(fd, TUNSETIFF, (void *)&ifr)) < 0 ) {
perror("ioctl(TUNSETIFF)");
close(fd);
return err;
}
strcpy(dev, ifr.ifr_name);
return fd;
}
main.c :
strcpy(tun_name, "tap0");
int tap_fd = tun_alloc(tun_name, IFF_TAP | IFF_NO_PI);
IFF_TAP (tap). IFF_NO_PI , .
tap0 /dev/ttyACM0. , tap_handler select:
while(1) {
int ret;
fd_set rd_set;
FD_ZERO(&rd_set);
/* tap_fd - tap inteface descriptor */
FD_SET(tap_fd, &rd_set);
/* tty_fd - /dev/ttyACM0 descriptor */
FD_SET(tty_fd, &rd_set);
ret = select(maxfd + 1, &rd_set, NULL, NULL, NULL);
. tap0 tap_handler STM32 ( : - 4 , , 2 - , ) /dev/ttyACM0. , :
if(FD_ISSET(tap_fd, &rd_set)) {
uint16_t nread = cread(tap_fd, buffer, BUFSIZE);
uint8_t buf[6];
*(uint32_t *)buf = PACKET_START_SIGN;
*(uint16_t *)(buf + 4) = nread;
cwrite(tty_fd,(char *)buf,6);
cwrite(tty_fd, buffer, nread);
delay_micro(delay_m);
}
/dev/ttyACM0, ( 4 ), , . tap :
if(FD_ISSET(tty_fd, &rd_set)) {
uint32_t sign;
/* */
int nread = read_n(tty_fd, (char *)&sign, sizeof(sign));
/* , */
if(nread == 0) {
break;
}
/* , 4 */
if(sign != PACKET_START_SIGN){
continue;
}
/* */
nread = read_n(tty_fd, (char *)&plength, 2);
if(nread == 0) {
break;
}
if (nread != 2){
continue;
}
/* , */
if(flag){
flag = 0;
nread = cread(tty_fd, buffer, sizeof(buffer));
if(nread != 6){
continue;
}
}
/* , */
if(plength > BUFSIZE){
break;
}
/* (plength ) tap interface*/
nread = read_n(tty_fd, buffer, plength);
if (nread != 0){
cwrite(tap_fd, buffer, nread);
delay_micro(delay_m);
}
}
STM32
USB CDC CubeMX HAL SPI1 .
callback' CDC_Receive_FS
( usbd_cdc_if.c), USB. , , ENC28J60. :
/* USB_POINTERS_ARRAY_SIZE - array_pos */
/* MAX_FRAMELEN - */
/* USB_BUFSIZE - */
extern uint8_t usb_buf[]; /* */
extern uint32_t pos_int; /* */
extern uint32_t array_pos[]; /* , */
extern uint32_t p_a; /* array_pos CDC_Receive_FS*/
extern uint32_t pl_a;/* array_pos */
/* USB_POINTERS_ARRAY_SIZE - array_pos */
/* MAX_FRAMELEN - */
/* USB_BUFSIZE - */
static int8_t CDC_Receive_FS(uint8_t* Buf, uint32_t *Len)
{
int8_t memok = 1;
/* , */
if( pl_a !=0 && p_a !=0){
int32_t mem_lag = array_pos[(p_a - 1) % USB_POINTERS_ARRAY_SIZE] - array_pos[(pl_a - 1) % USB_POINTERS_ARRAY_SIZE];
if(mem_lag > USB_BUFSIZE - MAX_FRAMELEN)
memok = 0;
}
/* ,
(array_pos) */
if(*Len < USB_BUFSIZE && *Len != 0 && memok){
uint16_t offset = pos_int % USB_BUFSIZE;
uint16_t new_pos = offset + *Len;
uint8_t split = 0;
if (new_pos > USB_BUFSIZE){
split = 1;
}
if(split){
int len1 = USB_BUFSIZE - offset;
int len2 = *Len - len1;
memcpy(usb_buf + offset, Buf, len1);
memcpy(usb_buf, Buf + len1, len2);
}
else
memcpy(usb_buf + offset, Buf, *Len);
pos_int += *Len;
array_pos[p_a % USB_POINTERS_ARRAY_SIZE] = pos_int;
p_a++;
}
USBD_CDC_SetRxBuffer(&hUsbDeviceFS, &Buf[0]);
USBD_CDC_ReceivePacket(&hUsbDeviceFS);
return (USBD_OK);
}
(main.c) ENC28J60:
if(pl_a < p_a){
uint32_t prev = 0;
if(pl_a > 0)
prev = array_pos[(pl_a - 1) % USB_POINTERS_ARRAY_SIZE];
/* ( ), CDC_Receive_FS */
int32_t n = array_pos[pl_a % USB_POINTERS_ARRAY_SIZE] - prev;//usb frame size
/* */
uint8_t *from = usb_buf + prev % USB_BUFSIZE;
/* */
uint8_t right_n = 1;
if (n < 0 || n > MAX_FRAMELEN){
right_n = 0;
}
/* . 6 ( 4 2 ) */
if((packet_len == 0) && packet_start && (n > 5) && right_n){
/* . */
uint32_t sign = read32(from,usb_buf);
/* 4 */
uint8_t *next = next_usb_ptr(from,usb_buf,4);
/* */
packet_size = read16(next,usb_buf);// 2 bytes after sign is packet length
/* */
if (packet_size > MAX_FRAMELEN || sign != PACKET_START_SIGN){
packet_size = 0;
}
else{
/* */
next = next_usb_ptr(from,usb_buf,6);
copy_buf(packet_buf, next, usb_buf, n - 6);
packet_len = n - 6;
packet_next_ptr = packet_buf + packet_len;
packet_start = 0;
}
}
/* */
else if(packet_len < packet_size && right_n){
/* */
copy_buf(packet_next_ptr, from, usb_buf, n);
packet_len += n;
packet_next_ptr = packet_buf + packet_len;
}
/* */
else if (packet_len > packet_size){
packet_len = 0;
packet_start = 1;
}
/* enc28j60 */
if(packet_len == packet_size && packet_size > 0){
enc28j60_packetSend(packet_buf, packet_size);
packet_len = 0;
packet_start = 1;
}
pl_a++;
}
ENC28J60 USB :
len = enc28j60_packetReceive(net_buf,sizeof(net_buf));
if (len > 0) {
*((uint16_t*)(sign_buf + 4)) = len;
while(CDC_Transmit_FS(sign_buf, sizeof(sign_buf)) == USBD_BUSY_CDC_TRANSMIT);
while(CDC_Transmit_FS(net_buf, len) == USBD_BUSY_CDC_TRANSMIT);
HAL_GPIO_TogglePin(GPIOC, GPIO_PIN_13);
}
CDC_Transmit_FS
, while. CDC_Transmit_FS
USBD_BUSY_CDC_TRANSMIT
USBD_BUSY
. :
if (hcdc->TxState != 0){
return USBD_BUSY_CDC_TRANSMIT;
}
ENC28J60 enc28j60_ini
, (promiscuous mode):
enc28j60_writeRegByte(ERXFCON,0);
Raspberry
eth0 ip . ping
sudo ifconfig eth0 up 10.0.0.2/24 ping 10.0.0.2
tcpdump:
sudo tcpdump -i eth0
STM32 , ENC28J60 raspberry. STM32 , arp / icmp ( ping). , /dev/ttyACM0:
ls /dev/ttyACM*
tap_handler:
gcc tap_handler.c -o tap_handler ./tap_handler
tap_handler - raspberry, tap0, , STM32, raspberry , .
.
raspberry ssh wi-fi , , default gateway. , raspberry :
sudo route del default gateway 192.168.1.1 sudo route add default gateway 10.0.0.2
DNS ( /etc/resolv.conf nameserver, , 8.8.8.8).
Raspberry
eth0 wlan0 NAT:
echo 1 | sudo tee -a /proc/sys/net/ipv4/ip_forward
sudo iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE
. , ( 0.5 /).
You don't have to bother with the raspberry, but directly connect the network wire from the router to the ENC28J60 (you need to turn off wi-fi on your computer and set the correct tap0 address). But testing is easier with raspberry, you can see everything that happens in tcpdump.
Why all this
Using such a bundle in life is probably not very convenient (especially if there are inexpensive usb ethernet adapters on sale), but it was very interesting to make it. Thanks for attention. Code link (project in Atollic TrueStudio).