# Question about NFC on Ameba RTL8195AM Dev Board
**URL:** https://forum.amebaiot.com/t/question-about-nfc-on-ameba-rtl8195am-dev-board/969
**Category:** SDK
**Created:** [December 10, 2021, 10:54am UTC](https://forum.amebaiot.com/t/question-about-nfc-on-ameba-rtl8195am-dev-board/969 "2021-12-10T10:54:37Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@walkerfleck](https://forum.amebaiot.com/u/walkerfleck)
#### Post date: [December 10, 2021, 10:54am UTC](https://forum.amebaiot.com/t/question-about-nfc-on-ameba-rtl8195am-dev-board/969/1 "2021-12-10T10:54:37Z")
Hi
I want to test NFC function on RTL8195AM Dev Board.
I have questions about NFC:
1. There are no example code, so I searched the package, found that there is nfc\_api.c. I write some test code for NFC, it did not working, I quote my code here:
```auto
#include "FreeRTOS.h"
#include "task.h"
#include "diag.h"
#include "device.h"
#include "main.h"
#include "log_uart_api.h"
#include "nfc_api.h"
nfctag_t nfcobj;
uint32_t nfcvalue;
void my_nfc_event_cb(void *arg, void *buf, unsigned int page) {
int i;
printf("\n\rNFC Event[%d] : ", page);
for(i=0;i<32;i++) {
printf("%02X ", ((unsigned char *)buf)[i]);
}
printf("\n\r");
}
void nfc_thread(void* arg) {
// ----------------------------------------------------
// Initial NFC Reader
printf("\n\rInitializing NFC ...\n\r");
nfc_init(&nfcobj, &nfcvalue);
while (1) {
printf("\n\rNFC Reading...\n\r");
nfc_read(&nfcobj, my_nfc_event_cb, NULL);
vTaskDelay(1500);
}
}
//========================================================================================================
void main(void) {
// ----------------------------------------------------
/* Initialize log uart and at command service */
console_init();
if(xTaskCreate(nfc_thread, ((const char*)"init"), 512 + 768, NULL, tskIDLE_PRIORITY + 3 + PRIORITIE_OFFSET, NULL) != pdPASS)
printf("\n\r%s xTaskCreate(nfc_thread) failed", __FUNCTION__ );
// ----------------------------------------------------
// FreeRTOS main loop
#if defined(CONFIG_KERNEL) && !TASK_SCHEDULER_DISABLED
#ifdef PLATFORM_FREERTOS
vTaskStartScheduler();
#endif
#else
RtlConsolTaskRom(NULL);
#endif
}
```
1. I found that R19 and R20 near the antenna are not connected, I guess the antenna is not powered. Should I soldering them directly?
Thanks for your help!
---
### Author:  [@wyy](https://forum.amebaiot.com/u/wyy)
#### Post date: [December 10, 2021, 2:35pm UTC](https://forum.amebaiot.com/t/question-about-nfc-on-ameba-rtl8195am-dev-board/969/2 "2021-12-10T14:35:42Z")
@walkerfleck
nfc example for the SDK can be found [here](https://github.com/ambiot/amb1_sdk/blob/master/project/realtek_ameba1_va0_example/example_sources/nfc/src/main.c).
yes, you will need to solder the leads to the nfc antenna for the example to work.
---
### Author:  [@walkerfleck](https://forum.amebaiot.com/u/walkerfleck)
#### Post date: [December 13, 2021, 4:25am UTC](https://forum.amebaiot.com/t/question-about-nfc-on-ameba-rtl8195am-dev-board/969/3 "2021-12-13T04:25:57Z")
Hi @wyy
Thanks, it is informative to me.
I have another question by the way, I found the example code is using thread, I suppose that it needs RtOS to run. I also found RtOS is needed for wifi functions, according to my test, the bare-metal mode seem not work for wifi APIs. Is that true that FreeRTOS is needed for some SDK functions?
---
### Author:  [@wyy](https://forum.amebaiot.com/u/wyy)
#### Post date: [December 13, 2021, 4:45am UTC](https://forum.amebaiot.com/t/question-about-nfc-on-ameba-rtl8195am-dev-board/969/4 "2021-12-13T04:45:34Z")
yes, bare-metal should work for the simpler peripheral functions (e.g. SPI, UART), but anything involving networking would probably need the RTOS.
---
### Author:  [@walkerfleck](https://forum.amebaiot.com/u/walkerfleck)
#### Post date: [December 13, 2021, 1:48pm UTC](https://forum.amebaiot.com/t/question-about-nfc-on-ameba-rtl8195am-dev-board/969/5 "2021-12-13T13:48:12Z")
Hi @wyy
I spent a lot of time to test the nfc example in GCC environment, there was a linking problem, which said the \_\_get\_IPSR() function is missing in cmsis.o. I googled for answer and added the function for it:
```auto
#pragma diag_suppress 994
__attribute__ ((naked))
uint32_t __get_IPSR(void)
{
__asm(" MRS R0, IPSR\n");
}
// Restore warnings about any non-void function not returning a value
#pragma diag_default 994
```
After image built, I flashed the image successfully. But the system hung and no response.
The UART log stopped like this:
I even can’t use the GDB, it hung after I entered “step” command at the first line of main().
Can’t figure out how to identify the problem.
---
### Author:  [@wyy](https://forum.amebaiot.com/u/wyy)
#### Post date: [December 15, 2021, 2:33am UTC](https://forum.amebaiot.com/t/question-about-nfc-on-ameba-rtl8195am-dev-board/969/6 "2021-12-15T02:33:59Z")
Hi @walkerfleck
It seems to be an issue with the CMSIS\_OS API layer, the \_\_get\_IPSR function is already defined, but it cant seem to find it.
After getting rid of all CMSIS\_OS function calls and replacing with FreeRTOS, I managed to get it working with my phone. It should also be possible to change the example to use no RTOS at all.
```auto
/*
* Routines to access hardware
*
* Copyright (c) 2015 Realtek Semiconductor Corp.
*
* This module is a confidential and proprietary property of RealTek and
* possession or use of this module requires written permission of RealTek.
*/
#include "FreeRTOS.h"
#include "task.h"
#include "diag.h"
#include "main.h"
#include "nfc_api.h"
#include "flash_api.h"
#define NFC_RESTORE_DEFAULT (0)
#define NFC_MAX_PAGE_NUM 36
nfctag_t nfctag;
unsigned int nfc_tag_content[NFC_MAX_PAGE_NUM];
unsigned char nfc_tag_dirty[NFC_MAX_PAGE_NUM];
#define RTK_NFC_UID 0x58
unsigned char nfc_default_uid[7] = {
RTK_NFC_UID, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06
};
unsigned int evt = 0;
#define FLASH_APP_NFC_BASE 0x85000
flash_t flash_nfc;
void nfc_event_listener(void *arg, unsigned int event) {
switch(event) {
case NFC_EV_READER_PRESENT:
DiagPrintf("NFC_EV_READER_PRESENT\r\n");
break;
case NFC_EV_READ:
DiagPrintf("NFC_EV_READ\r\n");
break;
case NFC_EV_WRITE:
DiagPrintf("NFC_EV_WRITE\r\n");
break;
case NFC_EV_ERR:
DiagPrintf("NFC_EV_ERR\r\n");
break;
case NFC_EV_CACHE_READ:
DiagPrintf("NFC_EV_CACHE_READ\r\n");
break;
}
}
/**
* This callback function is called several times if tag is being written multiple pages.
* DO NOT put heavy task here otherwise it will block tag write and cause timeout failure.
**/
void nfc_write_listener(void *arg, unsigned int page, unsigned int pgdat) {
nfc_tag_content[page] = pgdat;
nfc_tag_dirty[page] = 1;
evt |= NFC_EV_WRITE;
}
int is_valid_nfc_uid() {
int valid_content = 1;
unsigned char uid[7];
unsigned char bcc[2];
uid[0] = (unsigned char)((nfc_tag_content[0] & 0x000000FF) >> 0);
uid[1] = (unsigned char)((nfc_tag_content[0] & 0x0000FF00) >> 8);
uid[2] = (unsigned char)((nfc_tag_content[0] & 0x00FF0000) >> 16);
bcc[0] = (unsigned char)((nfc_tag_content[0] & 0xFF000000) >> 24);
uid[3] = (unsigned char)((nfc_tag_content[1] & 0x000000FF) >> 0);
uid[4] = (unsigned char)((nfc_tag_content[1] & 0x0000FF00) >> 8);
uid[5] = (unsigned char)((nfc_tag_content[1] & 0x00FF0000) >> 16);
uid[6] = (unsigned char)((nfc_tag_content[1] & 0xFF000000) >> 24);
bcc[1] = (unsigned char)((nfc_tag_content[2] & 0x000000FF) >> 0);
// verify Block Check Character
if (bcc[0] != (0x88 ^ uid[0] ^ uid[1] ^ uid[2])) {
valid_content = 0;
}
if (bcc[1] != (uid[3] ^ uid[4] ^ uid[5] ^ uid[6])) {
valid_content = 0;
}
return valid_content;
}
unsigned int generate_default_tag_content() {
unsigned int page_size = 0;
memset(nfc_tag_content, 0, NFC_MAX_PAGE_NUM * sizeof(unsigned int));
// calculate Block Check Character
unsigned char bcc[2];
bcc[0] = 0x88 ^ nfc_default_uid[0] ^ nfc_default_uid[1] ^ nfc_default_uid[2];
bcc[1] = nfc_default_uid[3] ^ nfc_default_uid[4] ^ nfc_default_uid[5] ^ nfc_default_uid[6];
// generate header
nfc_tag_content[page_size++] = ((unsigned int)nfc_default_uid[0]) << 0 |
((unsigned int)nfc_default_uid[1]) << 8 |
((unsigned int)nfc_default_uid[2]) << 16 |
((unsigned int) bcc[0]) << 24;
nfc_tag_content[page_size++] = ((unsigned int)nfc_default_uid[3]) << 0 |
((unsigned int)nfc_default_uid[4]) << 8 |
((unsigned int)nfc_default_uid[5]) << 16 |
((unsigned int)nfc_default_uid[6]) << 24;
nfc_tag_content[page_size++] = ((unsigned int) bcc[1]) << 0;
nfc_tag_content[page_size++] = 0x001211E1;
// Init tag content as NDEF will-known text message "HELLO WORLD!" in little endian
nfc_tag_content[page_size++] = 0x01d11303;
nfc_tag_content[page_size++] = 0x6502540f;
nfc_tag_content[page_size++] = 0x4c45486e;
nfc_tag_content[page_size++] = 0x57204f4c;
nfc_tag_content[page_size++] = 0x444c524f;
nfc_tag_content[page_size++] = 0x0000fe21;
return page_size;
}
void nfc_load_tag_content_from_flash() {
int i, address, page_size;
memset(nfc_tag_content, 0, NFC_MAX_PAGE_NUM * sizeof(unsigned int));
memset(nfc_tag_dirty, 0, NFC_MAX_PAGE_NUM);
for (i = 0, address = FLASH_APP_NFC_BASE; i < NFC_MAX_PAGE_NUM; i++, address+=4) {
flash_read_word(&flash_nfc, address, &nfc_tag_content[i]);
}
if (!is_valid_nfc_uid() || NFC_RESTORE_DEFAULT) {
DiagPrintf("Invalid tag content, restore to default value\r\n");
page_size = generate_default_tag_content();
// update to flash
flash_erase_sector(&flash_nfc, FLASH_APP_NFC_BASE);
for (i = 0, address = FLASH_APP_NFC_BASE; i < page_size; i++, address += 4) {
flash_write_word(&flash_nfc, address, nfc_tag_content[i]);
}
}
}
void nfc_store_tag_content() {
int i, address;
int modified_page_count;
// dump the modified tag content
modified_page_count = 0;
for (i = 4; i < NFC_MAX_PAGE_NUM && nfc_tag_dirty[i]; i++) {
modified_page_count++;
DiagPrintf("page:%02d data:%08x\r\n", i, nfc_tag_content[i]);
}
// update to cache from page 4
nfc_cache_write(&nfctag, &(nfc_tag_content[4]), 4, modified_page_count);
modified_page_count += 4; // we also need update tag header to flash which has size 4
flash_erase_sector(&flash_nfc, FLASH_APP_NFC_BASE);
for (i = 0, address = FLASH_APP_NFC_BASE; i < modified_page_count; i++, address += 4) {
flash_write_word(&flash_nfc, address, nfc_tag_content[i]);
}
}
void nfc_task(void const *arg) {
int i;
//osEvent evt;
nfc_load_tag_content_from_flash();
nfc_init(&nfctag, nfc_tag_content);
nfc_event(&nfctag, nfc_event_listener, NULL, 0xFF);
nfc_write(&nfctag, nfc_write_listener, NULL);
evt &= ~NFC_EV_WRITE;
while(1) {
if (evt & NFC_EV_WRITE) {
//osDelay(300);
vTaskDelay(300/portTICK_RATE_MS);
nfc_store_tag_content();
memset(nfc_tag_dirty, 0, NFC_MAX_PAGE_NUM);
evt &= ~NFC_EV_WRITE;
}
}
}
/**
* @brief Main program.
* @param None
* @retval None
*/
void main(void)
{
xTaskCreate(nfc_task, ((const char*)"nfc_thread"), 1024, NULL, tskIDLE_PRIORITY + 1, NULL);
DBG_INFO_MSG_OFF(_DBG_SPI_FLASH_);
//3 3)Enable Schedule, Start Kernel
#if defined(CONFIG_KERNEL) && !TASK_SCHEDULER_DISABLED
#ifdef PLATFORM_FREERTOS
vTaskStartScheduler();
#endif
#else
RtlConsolTaskRom(NULL);
#endif
while(1);
}
```
---
### Author:  [@walkerfleck](https://forum.amebaiot.com/u/walkerfleck)
#### Post date: [December 17, 2021, 4:34am UTC](https://forum.amebaiot.com/t/question-about-nfc-on-ameba-rtl8195am-dev-board/969/7 "2021-12-17T04:34:05Z")
Yeah, It’s the issue from CMSIS\_OS API, it worked from my side also, after I removed all CMSIS\_OS API calls.
Thanks a lot!