diff --git a/Makefile b/Makefile index 8096e439..d14c8dd2 100644 --- a/Makefile +++ b/Makefile @@ -5,6 +5,8 @@ GOSSAMER_PATH=gossamer # or omit it and provide it on the command line (make BOARD=foo). BOARD=sensorwatch_green +TINYUSB_CDC=1 + # Leave this line here. include $(GOSSAMER_PATH)/make.mk @@ -25,17 +27,23 @@ endif # Add your include directories here. INCLUDES += \ + -I./tinyusb/src \ -I./watch-library/shared/watch \ + -I./watch-library/hardware/watch \ # Add your source files here. SRCS += \ + ./watch-library/hardware/watch/watch.c \ ./watch-library/hardware/watch/watch_adc.c \ ./watch-library/hardware/watch/watch_extint.c \ ./watch-library/hardware/watch/watch_gpio.c \ + ./watch-library/hardware/watch/watch_private.c \ ./watch-library/hardware/watch/watch_rtc.c \ ./watch-library/hardware/watch/watch_slcd.c \ ./watch-library/shared/watch/watch_common_display.c \ ./watch-library/hardware/watch/watch_tcc.c \ + ./watch-library/hardware/watch/watch_usb_descriptors.c \ + ./watch-library/hardware/watch/watch_usb_cdc.c \ ./app.c \ # Finally, leave this line at the bottom of the file. diff --git a/app.c b/app.c index 3da6b45e..ab7e9dd2 100644 --- a/app.c +++ b/app.c @@ -1,9 +1,29 @@ #include #include "app.h" #include "watch.h" +#include "watch_private.h" #include "delay.h" +#include "usb.h" +#include "tusb.h" +#include "watch_usb_cdc.h" + +void yield(void) { + tud_task(); + cdc_task(); +} void app_init(void) { + // perform watch initialization first! + _watch_init(); + + // check if we are plugged into USB power. + HAL_GPIO_VBUS_DET_in(); + HAL_GPIO_VBUS_DET_pulldown(); + if (HAL_GPIO_VBUS_DET_read()){ + /// if so, enable USB functionality. + _watch_enable_usb(); + } + HAL_GPIO_VBUS_DET_off(); } void app_setup(void) { @@ -16,6 +36,11 @@ bool app_loop(void) { char buf[7]; snprintf(buf, 7, "%6d", vcc); watch_display_main_line(buf); + printf("VCC: %d\n", vcc); + + if (usb_is_enabled()) { + yield(); + } return false; } \ No newline at end of file diff --git a/watch-library/hardware/watch/watch_private.c b/watch-library/hardware/watch/watch_private.c index da593f50..0eb0cb45 100644 --- a/watch-library/hardware/watch/watch_private.c +++ b/watch-library/hardware/watch/watch_private.c @@ -23,13 +23,15 @@ */ #include "watch_private.h" -#include "watch_private_cdc.h" -#include "watch_utility.h" -#include "tusb.h" +#include "adc.h" +#include "tcc.h" +#include "tc.h" +#include "usb.h" +#include "system.h" void _watch_init(void) { - // disable the LED pin (it may have been enabled by the bootloader) - watch_disable_digital_output(GPIO(GPIO_PORTA, 20)); + // set frequency to 4 MHz + set_cpu_frequency(4000000); // disable debugger hot-plugging HAL_GPIO_SWCLK_pmuxdis(); @@ -131,286 +133,11 @@ int getentropy(void *buf, size_t buflen) { return 0; } -void _watch_enable_tc0(void) { - // before we init TinyUSB, we are going to need a periodic callback to handle TinyUSB tasks. - // TC2 and TC3 are reserved for devices on the 9-pin connector, so let's use TC0. - // clock TC0 with the 8 MHz clock on GCLK0. - hri_gclk_write_PCHCTRL_reg(GCLK, TC0_GCLK_ID, GCLK_PCHCTRL_GEN_GCLK0_Val | GCLK_PCHCTRL_CHEN); - // and enable the peripheral clock. - hri_mclk_set_APBCMASK_TC0_bit(MCLK); - // disable and reset TC0. - hri_tc_clear_CTRLA_ENABLE_bit(TC0); - hri_tc_wait_for_sync(TC0, TC_SYNCBUSY_ENABLE); - hri_tc_write_CTRLA_reg(TC0, TC_CTRLA_SWRST); - hri_tc_wait_for_sync(TC0, TC_SYNCBUSY_SWRST); - hri_tc_write_CTRLA_reg(TC0, TC_CTRLA_PRESCALER_DIV1024 | // divide the 8 MHz clock by 1024 to count at 7812.5 Hz - TC_CTRLA_MODE_COUNT8 | // count in 8-bit mode - TC_CTRLA_RUNSTDBY); // run in standby, just in case we figure that out - hri_tccount8_write_PER_reg(TC0, 10); // 7812.5 Hz / 10 = 781.125 Hz - // set an interrupt on overflow; this will call TC0_Handler below. - hri_tc_set_INTEN_OVF_bit(TC0); - - // set priority higher than TC1 - NVIC_SetPriority(TC0_IRQn, 5); - NVIC_ClearPendingIRQ(TC0_IRQn); - NVIC_EnableIRQ(TC0_IRQn); - - // Start the timer - hri_tc_set_CTRLA_ENABLE_bit(TC0); -} - -void _watch_disable_tc0(void) { - NVIC_DisableIRQ(TC0_IRQn); - NVIC_ClearPendingIRQ(TC0_IRQn); - hri_tc_clear_CTRLA_ENABLE_bit(TC0); - hri_tc_wait_for_sync(TC0, TC_SYNCBUSY_ENABLE); - hri_tc_write_CTRLA_reg(TC0, TC_CTRLA_SWRST); - hri_tc_wait_for_sync(TC0, TC_SYNCBUSY_SWRST); -} - -void _watch_enable_tc1(void) { - hri_gclk_write_PCHCTRL_reg(GCLK, TC1_GCLK_ID, GCLK_PCHCTRL_GEN_GCLK0_Val | GCLK_PCHCTRL_CHEN); - // and enable the peripheral clock. - hri_mclk_set_APBCMASK_TC1_bit(MCLK); - // disable and reset TC1. - hri_tc_clear_CTRLA_ENABLE_bit(TC1); - hri_tc_wait_for_sync(TC1, TC_SYNCBUSY_ENABLE); - hri_tc_write_CTRLA_reg(TC1, TC_CTRLA_SWRST); - hri_tc_wait_for_sync(TC1, TC_SYNCBUSY_SWRST); - hri_tc_write_CTRLA_reg(TC1, TC_CTRLA_PRESCALER_DIV1024 | // divide the 8 MHz clock by 1024 to count at 7812.5 Hz - TC_CTRLA_MODE_COUNT8 | // count in 8-bit mode - TC_CTRLA_RUNSTDBY); // run in standby, just in case we figure that out - hri_tccount8_write_PER_reg(TC1, 20); // 7812.5 Hz / 50 = 156.25 Hz - // set an interrupt on overflow; this will call TC1_Handler below. - hri_tc_set_INTEN_OVF_bit(TC1); - - // set priority lower than TC0 - NVIC_SetPriority(TC1_IRQn, 6); - NVIC_ClearPendingIRQ(TC1_IRQn); - NVIC_EnableIRQ(TC1_IRQn); - - // Start the timer - hri_tc_set_CTRLA_ENABLE_bit(TC1); -} - -void _watch_disable_tc1(void) { - NVIC_DisableIRQ(TC1_IRQn); - NVIC_ClearPendingIRQ(TC1_IRQn); - hri_tc_clear_CTRLA_ENABLE_bit(TC1); - hri_tc_wait_for_sync(TC1, TC_SYNCBUSY_ENABLE); - hri_tc_write_CTRLA_reg(TC1, TC_CTRLA_SWRST); - hri_tc_wait_for_sync(TC1, TC_SYNCBUSY_SWRST); -} - -void TC0_Handler(void) { - tud_task(); - TC0->COUNT8.INTFLAG.reg |= TC_INTFLAG_OVF; -} - -void TC1_Handler(void) { - cdc_task(); - TC1->COUNT8.INTFLAG.reg |= TC_INTFLAG_OVF; -} void _watch_enable_usb(void) { - // disable USB, just in case. - hri_usb_clear_CTRLA_ENABLE_bit(USB); - - // bump clock up to 8 MHz - hri_oscctrl_write_OSC16MCTRL_FSEL_bf(OSCCTRL, OSCCTRL_OSC16MCTRL_FSEL_8_Val); - - // reset flags and disable DFLL - OSCCTRL->INTFLAG.reg = OSCCTRL_INTFLAG_DFLLRDY; - OSCCTRL->DFLLCTRL.reg = 0; - while (!(OSCCTRL->STATUS.reg & OSCCTRL_STATUS_DFLLRDY)); - - // set the coarse and fine values to speed up frequency lock. - uint32_t coarse =(*((uint32_t *)NVMCTRL_OTP5)) >> 26; - OSCCTRL->DFLLVAL.reg = OSCCTRL_DFLLVAL_COARSE(coarse) | - OSCCTRL_DFLLVAL_FINE(0x200); - // set coarse and fine steps, and multiplier (48 MHz = 32768 Hz * 1465) - OSCCTRL->DFLLMUL.reg = OSCCTRL_DFLLMUL_CSTEP( 1 ) | - OSCCTRL_DFLLMUL_FSTEP( 1 ) | - OSCCTRL_DFLLMUL_MUL( 1465 ); - // set closed loop mode, chill cycle disable and USB clock recovery mode, and enable the DFLL. - OSCCTRL->DFLLCTRL.reg = OSCCTRL_DFLLCTRL_MODE | OSCCTRL_DFLLCTRL_CCDIS | OSCCTRL_DFLLCTRL_ONDEMAND | OSCCTRL_DFLLCTRL_RUNSTDBY | OSCCTRL_DFLLCTRL_USBCRM | OSCCTRL_DFLLCTRL_ENABLE; - while (!(OSCCTRL->STATUS.reg & OSCCTRL_STATUS_DFLLRDY)); - - // assign DFLL to GCLK1 - GCLK->GENCTRL[1].reg = GCLK_GENCTRL_SRC(GCLK_GENCTRL_SRC_DFLL48M) | GCLK_GENCTRL_DIV(1) | GCLK_GENCTRL_GENEN;// | GCLK_GENCTRL_OE; - while (GCLK->SYNCBUSY.bit.GENCTRL1); // wait for generator control 1 to sync - - // assign GCLK1 to USB - hri_gclk_write_PCHCTRL_reg(GCLK, USB_GCLK_ID, GCLK_PCHCTRL_GEN_GCLK1_Val | GCLK_PCHCTRL_CHEN); - hri_mclk_set_AHBMASK_USB_bit(MCLK); - hri_mclk_set_APBBMASK_USB_bit(MCLK); - - // USB Pin Init - gpio_set_pin_direction(PIN_PA24, GPIO_DIRECTION_OUT); - gpio_set_pin_level(PIN_PA24, false); - gpio_set_pin_pull_mode(PIN_PA24, GPIO_PULL_OFF); - gpio_set_pin_direction(PIN_PA25, GPIO_DIRECTION_OUT); - gpio_set_pin_level(PIN_PA25, false); - gpio_set_pin_pull_mode(PIN_PA25, GPIO_PULL_OFF); - - gpio_set_pin_function(PIN_PA24, PINMUX_PA24G_USB_DM); - gpio_set_pin_function(PIN_PA25, PINMUX_PA25G_USB_DP); - - _watch_enable_tc0(); - - tusb_init(); - - _watch_enable_tc1(); -} - -void USB_Handler(void) { - tud_int_handler(0); -} - -// USB Descriptors and tinyUSB callbacks follow. - -/* - * The MIT License (MIT) - * - * Copyright (c) 2019 Ha Thach (tinyusb.org) - * - * Permission is hereby granted, free of charge, to any person obtaining a copy - * of this software and associated documentation files (the "Software"), to deal - * in the Software without restriction, including without limitation the rights - * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell - * copies of the Software, and to permit persons to whom the Software is - * furnished to do so, subject to the following conditions: - * - * The above copyright notice and this permission notice shall be included in - * all copies or substantial portions of the Software. - * - * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR - * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, - * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE - * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER - * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, - * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN - * THE SOFTWARE. - * - */ - -//--------------------------------------------------------------------+ -// Device Descriptors -//--------------------------------------------------------------------+ -tusb_desc_device_t const desc_device = -{ - .bLength = sizeof(tusb_desc_device_t), - .bDescriptorType = TUSB_DESC_DEVICE, - .bcdUSB = 0x0200, - - // Use Interface Association Descriptor (IAD) for CDC - // As required by USB Specs IAD's subclass must be common class (2) and protocol must be IAD (1) - .bDeviceClass = TUSB_CLASS_MISC, - .bDeviceSubClass = MISC_SUBCLASS_COMMON, - .bDeviceProtocol = MISC_PROTOCOL_IAD, - - .bMaxPacketSize0 = CFG_TUD_ENDPOINT0_SIZE, - - .idVendor = 0x1209, - .idProduct = 0x2151, - .bcdDevice = 0x0100, - - .iManufacturer = 0x01, - .iProduct = 0x02, - .iSerialNumber = 0x03, - - .bNumConfigurations = 0x01 -}; - -// Invoked when received GET DEVICE DESCRIPTOR -// Application return pointer to descriptor -uint8_t const * tud_descriptor_device_cb(void) { - return (uint8_t const *) &desc_device; -} - -//--------------------------------------------------------------------+ -// Configuration Descriptor -//--------------------------------------------------------------------+ - -enum { - ITF_NUM_CDC = 0, - ITF_NUM_CDC_DATA, - ITF_NUM_TOTAL -}; - -#define CONFIG_TOTAL_LEN (TUD_CONFIG_DESC_LEN + TUD_CDC_DESC_LEN) - -#define EPNUM_CDC_NOTIF 0x81 -#define EPNUM_CDC_OUT 0x02 -#define EPNUM_CDC_IN 0x82 - - -uint8_t const desc_fs_configuration[] = { - // Config number, interface count, string index, total length, attribute, power in mA - TUD_CONFIG_DESCRIPTOR(1, ITF_NUM_TOTAL, 0, CONFIG_TOTAL_LEN, TUSB_DESC_CONFIG_ATT_REMOTE_WAKEUP, 100), - - // Interface number, string index, EP notification address and size, EP data address (out, in) and size. - TUD_CDC_DESCRIPTOR(ITF_NUM_CDC, 4, EPNUM_CDC_NOTIF, 8, EPNUM_CDC_OUT, EPNUM_CDC_IN, 64), -}; - -// Invoked when received GET CONFIGURATION DESCRIPTOR -// Application return pointer to descriptor -// Descriptor contents must exist long enough for transfer to complete -uint8_t const * tud_descriptor_configuration_cb(uint8_t index) { - (void) index; // for multiple configurations - return desc_fs_configuration; -} - -//--------------------------------------------------------------------+ -// String Descriptors -//--------------------------------------------------------------------+ - -// array of pointer to string descriptors -char const* string_desc_arr [] = -{ - (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409) - "TinyUSB", // 1: Manufacturer - "TinyUSB Device", // 2: Product - "123456", // 3: Serials, should use chip ID - "TinyUSB CDC", // 4: CDC Interface -}; - -static uint16_t _desc_str[32]; - -// Invoked when received GET STRING DESCRIPTOR request -// Application return pointer to descriptor, whose contents must exist long enough for transfer to complete -uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid) -{ - (void) langid; - - uint8_t chr_count; - - if ( index == 0) { - memcpy(&_desc_str[1], string_desc_arr[0], 2); - chr_count = 1; - } else { - // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors. - // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors - - if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL; - - const char* str = string_desc_arr[index]; - - // Cap at max char - chr_count = strlen(str); - if ( chr_count > 31 ) chr_count = 31; - - // Convert ASCII string into UTF-16 - for(uint8_t i=0; i - -#include "watch_utility.h" +#include "watch_usb_cdc.h" #include "tusb.h" /* @@ -51,16 +48,6 @@ static char s_read_buf[CDC_READ_BUF_SZ] = {0}; static size_t s_read_buf_pos = 0; static size_t s_read_buf_len = 0; -// Mask TC1 interrupts, preventing calls to cdc_task() -static inline void prv_critical_section_enter(void) { - NVIC_DisableIRQ(TC1_IRQn); -} - -// Unmask TC1 interrupts, allowing calls to cdc_task() -static inline void prv_critical_section_exit(void) { - NVIC_EnableIRQ(TC1_IRQn); -} - int _write(int file, char *ptr, int len) { (void) file; @@ -70,8 +57,6 @@ int _write(int file, char *ptr, int len) { int bytes_written = 0; - prv_critical_section_enter(); - for (int i = 0; i < len; i++) { s_write_buf[s_write_buf_pos] = ptr[i]; s_write_buf_pos = CDC_WRITE_BUF_IDX(s_write_buf_pos + 1); @@ -81,18 +66,13 @@ int _write(int file, char *ptr, int len) { bytes_written++; } - prv_critical_section_exit(); - return bytes_written; } int _read(int file, char *ptr, int len) { (void) file; - prv_critical_section_enter(); - if (ptr == NULL || len <= 0 || s_read_buf_len == 0) { - prv_critical_section_exit(); return -1; } @@ -113,8 +93,6 @@ int _read(int file, char *ptr, int len) { s_read_buf_len -= len; s_read_buf_pos = CDC_READ_BUF_IDX(s_read_buf_pos - len); - prv_critical_section_exit(); - return len; } diff --git a/watch-library/hardware/watch/watch_private_cdc.h b/watch-library/hardware/watch/watch_usb_cdc.h similarity index 93% rename from watch-library/hardware/watch/watch_private_cdc.h rename to watch-library/hardware/watch/watch_usb_cdc.h index b7fa9585..4559ff73 100644 --- a/watch-library/hardware/watch/watch_private_cdc.h +++ b/watch-library/hardware/watch/watch_usb_cdc.h @@ -23,11 +23,8 @@ * SOFTWARE. */ -#ifndef _WATCH_PRIVATE_CDC_H_INCLUDED -#define _WATCH_PRIVATE_CDC_H_INCLUDED +#pragma once int _write(int file, char *ptr, int len); int _read(int file, char *ptr, int len); void cdc_task(void); - -#endif diff --git a/watch-library/hardware/watch/watch_usb_descriptors.c b/watch-library/hardware/watch/watch_usb_descriptors.c new file mode 100644 index 00000000..2c24b077 --- /dev/null +++ b/watch-library/hardware/watch/watch_usb_descriptors.c @@ -0,0 +1,154 @@ +/* + * The MIT License (MIT) + * + * Copyright (c) 2019 Ha Thach (tinyusb.org) + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN + * THE SOFTWARE. + * + */ + +#include "tusb.h" + +//--------------------------------------------------------------------+ +// Device Descriptors +//--------------------------------------------------------------------+ +tusb_desc_device_t const desc_device = { + .bLength = sizeof(tusb_desc_device_t), + .bDescriptorType = TUSB_DESC_DEVICE, + .bcdUSB = 0x0200, + + // Use Interface Association Descriptor (IAD) for CDC + // As required by USB Specs IAD's subclass must be common class (2) and protocol must be IAD (1) + .bDeviceClass = TUSB_CLASS_MISC, + .bDeviceSubClass = MISC_SUBCLASS_COMMON, + .bDeviceProtocol = MISC_PROTOCOL_IAD, + + .bMaxPacketSize0 = CFG_TUD_ENDPOINT0_SIZE, + + .idVendor = 0x1209, + .idProduct = 0x2151, + .bcdDevice = 0x0100, + + .iManufacturer = 0x01, + .iProduct = 0x02, + .iSerialNumber = 0x03, + + .bNumConfigurations = 0x01 +}; + +// Invoked when received GET DEVICE DESCRIPTOR +// Application return pointer to descriptor +uint8_t const * tud_descriptor_device_cb(void) { + return (uint8_t const *) &desc_device; +} + +//--------------------------------------------------------------------+ +// Configuration Descriptor +//--------------------------------------------------------------------+ + +enum { + ITF_NUM_CDC = 0, + ITF_NUM_CDC_DATA, + ITF_NUM_TOTAL +}; + +#define CONFIG_TOTAL_LEN (TUD_CONFIG_DESC_LEN + TUD_CDC_DESC_LEN) + +#define EPNUM_CDC_NOTIF 0x81 +#define EPNUM_CDC_OUT 0x02 +#define EPNUM_CDC_IN 0x82 + +uint8_t const desc_fs_configuration[] = { + // Config number, interface count, string index, total length, attribute, power in mA + TUD_CONFIG_DESCRIPTOR(1, ITF_NUM_TOTAL, 0, CONFIG_TOTAL_LEN, TUSB_DESC_CONFIG_ATT_REMOTE_WAKEUP, 100), + + // Interface number, string index, EP notification address and size, EP data address (out, in) and size. + TUD_CDC_DESCRIPTOR(ITF_NUM_CDC, 4, EPNUM_CDC_NOTIF, 8, EPNUM_CDC_OUT, EPNUM_CDC_IN, 64), +}; + +// Invoked when received GET CONFIGURATION DESCRIPTOR +// Application return pointer to descriptor +// Descriptor contents must exist long enough for transfer to complete +uint8_t const * tud_descriptor_configuration_cb(uint8_t index) { + (void) index; // for multiple configurations + return desc_fs_configuration; +} + +//--------------------------------------------------------------------+ +// String Descriptors +//--------------------------------------------------------------------+ + +static char serialnum[32 * 2 + 1] = {'\0'}; // 2 chars per hexnumber + '\0' + +// array of pointer to string descriptors +char const* string_desc_arr [] = { + (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409) + "Oddly Specific Objects", // 1: Manufacturer + "Sensor Watch", // 2: Product + serialnum, // 3: Serial number + "TinyUSB CDC", // 4: CDC Interface +}; + +static uint16_t _desc_str[32]; +static bool serial_number_written = false; + +// Invoked when received GET STRING DESCRIPTOR request +// Application return pointer to descriptor, whose contents must exist long enough for transfer to complete +uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid) { + (void) langid; + uint8_t chr_count; + + if (!serial_number_written) { + // Generate serial number based on chip unique ID + uint32_t chipid[4]; + chipid[0] = *((uint32_t *)0x0080A00C); + chipid[1] = *((uint32_t *)0x0080A040); + chipid[2] = *((uint32_t *)0x0080A044); + chipid[3] = *((uint32_t *)0x0080A048); + + sprintf(serialnum, "%08lX%08lX%08lX%08lX", chipid[0], chipid[1], chipid[2], chipid[3]); + serial_number_written = true; + } + + if (index == 0) { + memcpy(&_desc_str[1], string_desc_arr[0], 2); + chr_count = 1; + } else { + // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors. + // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors + + if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL; + + const char* str = string_desc_arr[index]; + + // Cap at max char + chr_count = strlen(str); + if ( chr_count > 31 ) chr_count = 31; + + // Convert ASCII string into UTF-16 + for(uint8_t i=0; i