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/*---------------------------------------------------------------------------*\
FILE........: usb_vcp_ut.c
AUTHOR......: xenovacivus
DATE CREATED: 31 August 2014
USB Virtual COM Port (VCP) unit test that I found here:
https://github.com/xenovacivus/STM32DiscoveryVCP
Remarkably, it compiled and ran first time, and even the LEDs blink
as advertised, they just happen to match the LEDs on the SM1000!
However the speed was capped at about 130 kB/s. After a lot of
messing around I found suggestions in the comments from a similar
library here:
http://stm32f4-discovery.com/2014/08/library-24-virtual-com-port-vcp-stm32f4xx/
The key was changing APP_RX_DATA_SIZE in usbd_conf.h to 10000. I
guess the previous size of 2048 was constraining the length of USB
packets, and the USB overhead meant slow throughput. I could
achieve a max of 450 kB/s with this change, about 1/3 of the
theoretical 1.5 MB/s max for USB FS (12 Mbit/s).
I used this to test grabbing data from the STM32F4 Discovery:
$ sudo dd if=/dev/ttyACM0 of=/dev/null count=100
4+96 records in
44+1 records out
22615 bytes (23 kB) copied, 0.150884 s, 150 kB/s
However I occasionally see:
$ sudo dd if=/dev/ttyACM0 of=/dev/null count=100
dd: failed to open ‘/dev/ttyACM0’: Device or resource busy
Googling found some suggestion that this is due to "modem manager", however I
removed MM and the problem still exists.
\*---------------------------------------------------------------------------*/
#include <stm32f4xx.h>
#include <stm32f4xx_gpio.h>
#include "stm32f4_usb_vcp.h"
#include "sm1000_leds_switches.h"
volatile uint32_t ticker, buf_ticker;
#define N 640*6
short buf[N];
int main(void) {
int i;
for(i=0; i<N; i++)
buf[i] = 0;
sm1000_leds_switches_init();
usb_vcp_init();
SysTick_Config(SystemCoreClock/1000);
while (1) {
/* Blink the discovery red LED at 1Hz */
if (ticker > 500) {
GPIOD->BSRRH = GPIO_Pin_13;
}
if (ticker > 1000) {
ticker = 0;
GPIOD->BSRRL = GPIO_Pin_13;
}
/* Every 40ms send a buffer, simulates 16 bit samples at Fs=96kHz */
if (buf_ticker > 40) {
buf_ticker = 0;
led_pwr(1);
VCP_send_buffer((uint8_t*)buf, sizeof(buf));
led_pwr(0);
}
}
return 0;
}
/*
* Interrupt Handler
*/
void SysTick_Handler(void)
{
ticker++;
buf_ticker++;
}
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