Posted on January 27, 2017 at 00:01That's good, it didn't sound reasonable. I am currently working on USB UARTs and just got it working.
My code was generated by cube for the STM32F407G-DISC1 board, so you can regen it for yours (if you wish). All I did was turn on the USB device, device FS, for CDC. Gen the code and then I put in the interface routines for GCC/newlib to use printf/scanf via USB.
Attached is main.c and the support file that has to be munged.
...and the widget to attach a file is gone... what the hell ST????
Sorry about the formatting, I tried but these tools suck.
main.c
...
int
main(
void
)
{
/* USER CODE BEGIN 1 */
/*
* a test program to see what it takes to get a USB
com
port working.
*
* To get the I/O to work, I put in the helpers to get stdio to work. This means
* _read and _write.
*
* The USB portion is handled by the code in usbd_cdc_if.c. All of the action happens there.
* Actually, the interface is pretty weird. The only public function is CDC_Transmit_FS. That means
* that there is no access to CDC_Receive_FS externally.
Wuh
?
*
* The unwritten interface is that you are supposed to
munge
usbd_cdc_if.c to be able to get at the read
* and write routines. So I placed _write in there, which calls CDC_Transmit_FS.
*
* _read is handled a little different. CDC_Receive_FS is a callback routine that is called by the USB stack
* once some data has been received. I ended up putting some code in there to dequeue the USB data and dump
* it into a secondary buffer. Once
getchar
/
scanf
/??? is called, _read will then go and attack the secondary
* buffer. Of course, _read only returns once the buffering is satisfied, so main calls
setvbuf
to clobber the
* stdio buffering.
*
* Since _read is blocking, I also threw in
kbhit
() to free up the processor.
*/
char
ch;
/* USER CODE END 1 */
/* MCU Configuration----------------------------------------------------------*/
/* Reset of all peripherals, Initializes the Flash interface and the
Systick
. */
HAL_Init();
/* Configure the system clock */
SystemClock_Config();
/* Initialize all configured peripherals */
MX_GPIO_Init();
MX_USB_DEVICE_Init();
/* USER CODE BEGIN 2 */
setvbuf
(stdin, NULL, _IONBF, 0);
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while
(1) {
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
if
(kbhit()) {
ch = getchar();
putchar(ch);
}
HAL_Delay(1);
}
/* USER CODE END 3 */
}
usbd_cdc_if.c:
/**
* @brief
CDC_Receive_FS
*
Data received over USB OUT
endpoint
are sent over CDC interface
*
through this function.
*
*
@note
*
This function will block any OUT packet reception on USB
endpoint
*
untill
exiting this function. If you exit this function before transfer
*
is complete on CDC interface (
ie
. using DMA controller) it will result
*
in receiving more data while previous ones are still not sent.
*
* @
param
Buf
: Buffer of data to be received
* @
param
Len
: Number of data received (in bytes)
* @
retval
Result of the operation: USBD_OK if all operations are OK else USBD_FAIL
*/
static
int8_t
CDC_Receive_FS (
uint8_t
* Buf,
uint32_t
*Len)
{
/* USER CODE BEGIN 6 */
USBD_CDC_SetRxBuffer(&hUsbDeviceFS, &Buf[0]);
USBD_CDC_ReceivePacket(&hUsbDeviceFS);
receivedLen = *Len;
memcpy
( &receivedData[totalReceived], Buf, receivedLen);
totalReceived += receivedLen;
return
(
USBD_OK);
/* USER CODE END 6 */
}
/**
* @brief
CDC_Transmit_FS
*
Data send over USB IN
endpoint
are sent over CDC interface
*
through this function.
*
@note
*
*
* @
param
Buf
: Buffer of data to be send
* @
param
Len
: Number of data to be send (in bytes)
* @
retval
Result of the operation: USBD_OK if all operations are OK else USBD_FAIL or USBD_BUSY
*/
uint8_t
CDC_Transmit_FS(
uint8_t
* Buf,
uint16_t
Len)
{
uint8_t
result =
USBD_OK
;
/* USER CODE BEGIN 7 */
USBD_CDC_HandleTypeDef
*hcdc = (
USBD_CDC_HandleTypeDef
*)hUsbDeviceFS.
pClassData
;
if
(hcdc->
TxState
!= 0){
return
USBD_BUSY;
}
USBD_CDC_SetTxBuffer(&hUsbDeviceFS, Buf, Len);
result = USBD_CDC_TransmitPacket(&hUsbDeviceFS);
/* USER CODE END 7 */
return
result;
}
/* USER CODE BEGIN PRIVATE_FUNCTIONS_IMPLEMENTATION */
/**
* @}
*/
int
_write(
int
file,
char
*outgoing,
int
len) {
if
(hUsbDeviceFS.
dev_state
== USBD_STATE_CONFIGURED){
CDC_Transmit_FS( outgoing, len);
}
return
len;
}
/**
* @}
*/
int
_read(
int
file,
char
* result,
size_t
len) {
if
(len == 0) {
return
(0);
}
while
(totalReceived < len) {
HAL_Delay(10);
}
memcpy
( result, receivedData, len);
totalReceived = 0;
return
(len);
}
/**
* @}
*/
bool kbhit(
void
) {
return
(totalReceived > 0);
}
