topic Re: NHS3152 - Measure resitance correct param ADC-I2D-DAC in LPC Microcontrollers

NHS3152 - Measure resitance correct param ADC-I2D-DAC

leo94 — Wed, 30 Sep 2020 11:13:46 GMT

Hello,

I am trying to create code following @driesmoors ' solution to Measure resitance: (NHS3152)

I have modified code from the example: mainndeft2t.c.

The program follows the following logic:

0. Wake up when NFC field is detected

(from dries's answer)

1. Set the configuration of the analog pins to IOCON_FUNC_

2. Connect the DAC to ANA1, set a continuous conversion of 1.25V (used: adcdac_nss_example_1)

3. Connect the I2D to ANA4, configure correctly and start a conversion. Only when a conversion is started, current will start flowing over your resistor. The current will continue to flow when the conversion ends. -> a (used: i2d_nss_example_1)

4. Connect the ADC to ANA4, and measure the voltage. -> v4 (used: adcdac_nss_example_3)

5. Connect the ADC to ANA1, and measure the voltage. -> v1

(New insturcitons)

6. R= V(V1-V2)/(I_pico * 10^-6)

7. Display resitance value on screen phone

I connected a 100KOHM resitor between ana1 and ana4. The code runs but i am not getting a close resistor value. I get the following results:

r=100[Kohm]

adc_1 = 1.34 [V]

adc_4 = 1.04 [V]

current_picoampere = 5*10^5 [pA]

which gives a low res = 0.3/0.5= 0.6 [Ohm]

I have the following questions:

How do i pass 1.25V ana1? (formula to convert the bits to ana value)
Why am i getting current_picoampere = 5*10^5? is this too high?
What gain to i pass I2D for 100kOHM, where can i find a table/formula to calculate this based on resistance ?
What errors are in the code that are giving me such a low res output ?

Here is the code:

/* FROM https://community.nxp.com/t5/NFC/Measure-resistance-NHS3152/m-p/831045 1. Set the configuration of the analog pins to IOCON_FUNC_1 2. Connect the DAC to ANA1, set a continuous conversion of 1.25V. 3. Connect the I2D to ANA4, configure correctly and start a conversion. Only when a conversion is started, current will start flowing over your resistor. The current will continue to flow when the conversion ends. -> a 4. Connect the ADC to ANA4, and measure the voltage. -> v4 5. Connect the ADC to ANA1, and measure the voltage. -> v1 */ /* ------------------------------------------------------------------------- */ #include <string.h> #include <stdlib.h> #include <stdio.h> // contains sprintf function (needs to be included to avoid : https://stackoverflow.com/questions/8440816/warning-implicit-declaration-of-function #include "board.h" #include "ndeft2t/ndeft2t.h" /* ------------------------------------------------------------------------- */ #define LOCALE "en" /**< Language used when creating TEXT records. */ #define MIME "nhs31xx/example.ndef" /**< Mime type used when creating MIME records. */ /** The URL will be used in a single-record NDEF message. */ #define MAX_URI_PAYLOAD (254 - NDEFT2T_MSG_OVERHEAD(true, NDEFT2T_URI_RECORD_OVERHEAD(true))) static const uint8_t sUrl[MAX_URI_PAYLOAD + 1 /* NUL */] = "nxp.com/NTAGSMARTSENSOR"; /** * The text and the MIME data are always presented together, in a dual-record NDEF message. * Payload length is split evenly between TEXT and MIME. */ #define MAX_TEXT_PAYLOAD (254 - (NDEFT2T_MSG_OVERHEAD(true, \ NDEFT2T_TEXT_RECORD_OVERHEAD(true, sizeof(LOCALE) - 1) + \ NDEFT2T_MIME_RECORD_OVERHEAD(true, sizeof(MIME) - 1)) / 2)) static uint8_t sText[MAX_TEXT_PAYLOAD] = "10 V1-V4"; /** @copydoc MAX_TEXT_PAYLOAD */ #define MAX_MIME_PAYLOAD MAX_TEXT_PAYLOAD static uint8_t sBytes[MAX_MIME_PAYLOAD] = {0, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE}; /* ------------------------------------------------------------------------- */ /** * Used to determine which NDEF message must be generated. * - @c true: generate a single-record NDEF message containing a URL. * - @c false: generate a dual-record NDEF message containing a TEXT and a MIME record. */ static bool sState; static volatile bool sButtonPressed = false; /** @c true when the WAKEUP button is pressed on the Demo PCB */ static volatile bool sMsgAvailable = false; /** @c true when a new NDEF message has been written by the tag reader. */ static volatile bool sFieldPresent = false; /** @c true when an NFC field is detected and the tag is selected. */ static void GenerateNdef_Url(void); static void GenerateNdef_TextMime(void); static void ParseNdef(void); /* ------------------------------------------------------------------------- */ //Store adc_1, adc_4, current and resistance value static volatile float adcInput_4 = 5.0; // 4. store V input 4 static volatile float adcInput_1 = 5.0; // 5. store V input 1 static volatile int current_native; // 3. store I2D ana 4 static volatile int current_picoampere; // 3. store I2D ana4 static volatile double resval = -1; // store resistance calculated: (dcInput_1-adcInput_4)/Current_picoampere*10e-6 static void adcdac_nss_example_1(void); //continuous DAC ana1 static void i2d_nss_example_1(void); //I2D ana4 static void adcdac_nss_example_3(void); //NEW single shot get ADC value ana4 static void adcdac_nss_example_3_2(void); //NEW single shot get ADC value ana1 /** * Handler for PIO0_0 / WAKEUP pin. * Overrides the WEAK function in the startup module. */ void PIO0_IRQHandler(void) { Chip_GPIO_ClearInts(NSS_GPIO, 0, 1); sButtonPressed = true; /* Handled in main loop */ } /** * Called under interrupt. * @see NDEFT2T_FIELD_STATUS_CB * @see pNdeft2t_FieldStatus_Cb_t */ void App_FieldStatusCb(bool status) { if (status) { LED_On(LED_RED); } else { LED_Off(LED_RED); } sFieldPresent = status; /* Handled in main loop */ } /** * Called under interrupt. * @see NDEFT2T_MSG_AVAILABLE_CB * @see pNdeft2t_MsgAvailable_Cb_t */ void App_MsgAvailableCb(void) { sMsgAvailable = true; /* Handled in main loop */ } /* ------------------------------------------------------------------------- */ /** Generates a single-record NDEF message containing a URL, and copies it to the NFC shared memory. */ static void GenerateNdef_Url(void) { uint8_t instance[NDEFT2T_INSTANCE_SIZE]; uint8_t buffer[NFC_SHARED_MEM_BYTE_SIZE]; NDEFT2T_CREATE_RECORD_INFO_T recordInfo = {.pString = NULL /* don't care */, .shortRecord = true, .uriCode = 0x01 /* "http://www." */}; NDEFT2T_CreateMessage(instance, buffer, NFC_SHARED_MEM_BYTE_SIZE, true); if (NDEFT2T_CreateUriRecord(instance, &recordInfo)) { if (NDEFT2T_WriteRecordPayload(instance, sUrl, (int)strlen((char *)sUrl))) { NDEFT2T_CommitRecord(instance); } } NDEFT2T_CommitMessage(instance); /* Copies the generated message to NFC shared memory. */ } /** Generates a dual-record NDEF message containing a TEXT and a MIME record, and copies it to the NFC shared memory. */ static void GenerateNdef_TextMime(void) { uint8_t instance[NDEFT2T_INSTANCE_SIZE]; uint8_t buffer[NFC_SHARED_MEM_BYTE_SIZE]; NDEFT2T_CREATE_RECORD_INFO_T textRecordInfo = {.pString = (uint8_t *)"en" /* language code */, .shortRecord = true, .uriCode = 0 /* don't care */}; NDEFT2T_CREATE_RECORD_INFO_T mimeRecordInfo = {.pString = (uint8_t *)MIME /* mime type */, .shortRecord = true, .uriCode = 0 /* don't care */}; NDEFT2T_CreateMessage(instance, buffer, NFC_SHARED_MEM_BYTE_SIZE, true); if (NDEFT2T_CreateTextRecord(instance, &textRecordInfo)) { if (NDEFT2T_WriteRecordPayload(instance, sText, sizeof(sText) - 1 /* exclude NUL char */)) { NDEFT2T_CommitRecord(instance); } } if (NDEFT2T_CreateMimeRecord(instance, &mimeRecordInfo)) { if (NDEFT2T_WriteRecordPayload(instance, sBytes, sizeof(sBytes))) { NDEFT2T_CommitRecord(instance); } } NDEFT2T_CommitMessage(instance); /* Copies the generated message to NFC shared memory. */ } /** Parses the NDEF message in the NFC shared memory, and copies the TEXT and MIME payloads. */ static void ParseNdef(void) { uint8_t instance[NDEFT2T_INSTANCE_SIZE]; uint8_t buffer[NFC_SHARED_MEM_BYTE_SIZE]; NDEFT2T_PARSE_RECORD_INFO_T recordInfo; int len = 0; uint8_t *pData = NULL; if (NDEFT2T_GetMessage(instance, buffer, NFC_SHARED_MEM_BYTE_SIZE)) { while (NDEFT2T_GetNextRecord(instance, &recordInfo) != false) { pData = (uint8_t *)NDEFT2T_GetRecordPayload(instance, &len); switch (recordInfo.type) { case NDEFT2T_RECORD_TYPE_TEXT: if ((size_t)len <= MAX_TEXT_PAYLOAD) { memcpy(sText, pData, (size_t)len); memset(sText + len, 0, MAX_TEXT_PAYLOAD - (size_t)len); } break; case NDEFT2T_RECORD_TYPE_MIME: if ((size_t)len <= MAX_MIME_PAYLOAD) { memcpy(sBytes, pData, (size_t)len); memset(sBytes + len, 0, MAX_MIME_PAYLOAD - (size_t)len); } break; default: /* ignore */ break; } } } } // 1. Set the configuration of the analog pins to IOCON_FUNC_1 // 2. Connect the DAC to ANA1, set a continuous conversion of 1.25V. void adcdac_nss_example_1(void) // Modified IOCON_ANA0_0 --> IOCON_ANA0_1 & ADCDAC_IO_ANA0_0 --> ADCDAC_IO_ANA0_1 { //! [adcdac_nss_example_1] Chip_IOCON_SetPinConfig(NSS_IOCON, IOCON_ANA0_1, IOCON_FUNC_1); // IOCON_FUN_1 Chip_ADCDAC_Init(NSS_ADCDAC0); Chip_ADCDAC_SetMuxDAC(NSS_ADCDAC0, ADCDAC_IO_ANA0_1); Chip_ADCDAC_SetModeDAC(NSS_ADCDAC0, ADCDAC_CONTINUOUS); Chip_ADCDAC_WriteOutputDAC(NSS_ADCDAC0, 3000); //! [adcdac_nss_example_1] } /* ------------------------------------------------------------------------- */ // 3. Connect the I2D to ANA4, configure correctly and start a conversion. Only when a conversion is started, current will start flowing over your resistor. The current will continue to flow when the conversion ends. -> a // FROM i2d_nss_example_1 void i2d_nss_example_1(void) { //! [i2d_nss_example_1] int i2dValue; int i2dNativeValue; Chip_IOCON_SetPinConfig(NSS_IOCON, IOCON_ANA0_4, IOCON_FUNC_1); // IOCON_FUN_1 Chip_I2D_Init(NSS_I2D); Chip_I2D_Setup(NSS_I2D, I2D_SINGLE_SHOT, I2D_SCALER_GAIN_10_1, I2D_CONVERTER_GAIN_HIGH, 100); Chip_I2D_SetMuxInput(NSS_I2D, I2D_INPUT_ANA0_4); Chip_I2D_Start(NSS_I2D); while (!(Chip_I2D_ReadStatus(NSS_I2D) & I2D_STATUS_CONVERSION_DONE)) { ; /* wait */ } i2dNativeValue = Chip_I2D_GetValue(NSS_I2D); i2dValue = Chip_I2D_NativeToPicoAmpere(i2dNativeValue, I2D_SCALER_GAIN_10_1, I2D_CONVERTER_GAIN_HIGH, 100); Chip_I2D_DeInit(NSS_I2D); //! [i2d_nss_example_1] current_native = i2dNativeValue; current_picoampere = i2dValue; } // 4. Connect the ADC to ANA4, and measure the voltage. -> v4 //FROM Example 3 - Single-shot Analog-to-Digital Conversion without IRQ // The conversion: adc_input_voltage = (native_value * 1.2V) / 2825 + 0.09V void adcdac_nss_example_3(void) // Modifications: IOCON_ANA0_5--> IOCON_ANA0_4 & converted adcinput_4= (adcInput_4 * 1.2) / 2825 + 0.09 { //! [adcdac_nss_example_3] Chip_IOCON_SetPinConfig(NSS_IOCON, IOCON_ANA0_4, IOCON_FUNC_1); //Chip_ADCDAC_Init(NSS_ADCDAC0); Chip_ADCDAC_SetMuxADC(NSS_ADCDAC0, ADCDAC_IO_ANA0_4); Chip_ADCDAC_SetInputRangeADC(NSS_ADCDAC0, ADCDAC_INPUTRANGE_WIDE); Chip_ADCDAC_SetModeADC(NSS_ADCDAC0, ADCDAC_SINGLE_SHOT); Chip_ADCDAC_StartADC(NSS_ADCDAC0); while (!(Chip_ADCDAC_ReadStatus(NSS_ADCDAC0) & ADCDAC_STATUS_ADC_DONE)) { ; /* Wait until measurement completes. For single-shot mode only! */ } adcInput_4 = Chip_ADCDAC_GetValueADC(NSS_ADCDAC0); adcInput_4= (adcInput_4 * 1.2) / 2825 + 0.09; // CONVERSION added line //! [adcdac_nss_example_3] } void adcdac_nss_example_3_2(void) // Modifications: IOCON_ANA0_5--> IOCON_ANA0_1 & converted adcinput_1= (adcInput_1 * 1.2) / 2825 + 0.09 { //! [adcdac_nss_example_3] Chip_IOCON_SetPinConfig(NSS_IOCON, IOCON_ANA0_1, IOCON_FUNC_1); //Chip_ADCDAC_Init(NSS_ADCDAC0); Chip_ADCDAC_SetMuxADC(NSS_ADCDAC0, ADCDAC_IO_ANA0_1); Chip_ADCDAC_SetInputRangeADC(NSS_ADCDAC0, ADCDAC_INPUTRANGE_WIDE); Chip_ADCDAC_SetModeADC(NSS_ADCDAC0, ADCDAC_SINGLE_SHOT); Chip_ADCDAC_StartADC(NSS_ADCDAC0); while (!(Chip_ADCDAC_ReadStatus(NSS_ADCDAC0) & ADCDAC_STATUS_ADC_DONE)) { ; /* Wait until measurement completes. For single-shot mode only! */ } adcInput_1 = Chip_ADCDAC_GetValueADC(NSS_ADCDAC0); adcInput_1= (adcInput_1 * 1.2) / 2825 + 0.09; // CONVERSION added line //! [adcdac_nss_example_3] } // MAIN int main(void) { Board_Init(); NDEFT2T_Init(); NVIC_EnableIRQ(PIO0_IRQn); /* PIO0_IRQHandler is called when this interrupt fires. */ Chip_GPIO_EnableInt(NSS_GPIO, 0, 1); // for ever, WHILE field is detected: 2. Connect the DAC to ANA1, set a continuous conversion of 1.25V. for (;;) { while (sFieldPresent) { // 2. Connect the DAC to ANA1 -output Voltage adcdac_nss_example_1(); // 3. Connect the I2D to ANA4, - read current ana4 through resistor i2d_nss_example_1(); // 4. Connect the ADC to ANA4, and measure the voltage. ->v4 adcdac_nss_example_3(); // 5. Connect the ADC to ANA1, and measure the voltage. -> v1 adcdac_nss_example_3_2(); // generate the message only once per field??? GenerateNdef_TextMime(); resval = (adcInput_1-adcInput_4)/(current_picoampere * 10e-5); // (v1-v4)/(I4pico * 10^-6) V/I=R [V/A =ohm] sprintf((char *)sText, "adc_1: %4.2f adc_4: %4.2f pA: %4.d res: %4.4f, nat: %4.d", adcInput_1, adcInput_4,current_picoampere, resval,current_native );//commented in from Thesis, changes payloadText to sText // attach message to be read if (sMsgAvailable) { sMsgAvailable = false; ParseNdef(); } } Chip_PMU_PowerMode_EnterDeepSleep(); } return 0; }

Thanks,

Leo

P.S. since the update to the community page with the subsequent series of emails for badges, all your emails have gone to spam - maybe this is happening to other clients of yours.

Re: NHS3152 - Measure resitance correct param ADC-I2D-DAC

driesmoors — Fri, 02 Oct 2020 06:03:23 GMT

Hello Leo,

Can you adjust the parameters in Chip_I2D_Setup? Given your expected current at 100kOhm, you'll need to use the 25uA range, which corresponds to these parameters:

Chip_I2D_Setup(NSS_I2D, I2D_SINGLE_SHOT, I2D_SCALER_GAIN_10_1, I2D_CONVERTER_GAIN_LOW, 100);

See also Chapter 8 Current-to-Digital converter (I2D) > Specifications in the datasheet.

The conversion from van pico Ampère to Ohm is then calculated as: resval = (adcInput_1 - adcInput_4) / (current_picoampere * 1e-12)

Let me know your results!

Best,
Dries.

Re: NHS3152 - Measure resitance correct param ADC-I2D-DAC

leo94 — Fri, 02 Oct 2020 14:16:44 GMT

Hi Dries,

Thanks for your help,

I updated Chip_I2D_Setup as suggested:

225 Chip_I2D_Setup(NSS_I2D, I2D_SINGLE_SHOT, I2D_SCALER_GAIN_10_1, I2D_CONVERTER_GAIN_LOW, 100);

and converted pico (this was emabrassing)

306 resval = (adcInput_1 - adcInput_4) / (current_picoampere * 1e-12)

i also changed output code:

307 sprintf((char *)sText, "adc_1: %6.2f adc_4: %6.2f current_picoampere: %8.d resistance: %e current_native: %6.d", adcInput_1, adcInput_4,current_picoampere, resval,current_native );

I get the following output:

adc_1:1.34 adc_4:0.58 current_picoampere:178980 resistance:4.241142e+06 current_native:8949
adc_1:1.34 adc_4:0.56 current_picoampere:179140 resistance:4.303748e+06 current_native: 8957
adc_1:1.34 adc_4:0.58 current_picoampere: 179220 resistance:4.249684e+06 current_native:8961

Possible things that could be affecting results:

I am running Debug--> resume connect via LPC-link 2. maybe running the code this way affects outcome?

I haven't connected anything to the GND pin of NHS3152 - only connection is ana1-resistor[100kOhm]-ana4

Possible conversion errors for V1, V4, I2D

Thanks,

leo

FULL NEW CODE:

/*
FROM https://community.nxp.com/t5/NFC/Measure-resistance-NHS3152/m-p/831045

1. Set the configuration of the analog pins to IOCON_FUNC_1
2. Connect the DAC to ANA1, set a continuous conversion of 1.25V.
3. Connect the I2D to ANA4, configure correctly and start a conversion. Only when a conversion is started, current will start flowing over your resistor. The current will continue to flow when the conversion ends. -> a
4. Connect the ADC to ANA4, and measure the voltage. -> v4
5. Connect the ADC to ANA1, and measure the voltage. -> v1

*/




/* ------------------------------------------------------------------------- */

#include <string.h>
#include <stdlib.h>
#include <stdio.h> // contains sprintf function (needs to be included to avoid : https://stackoverflow.com/questions/8440816/warning-implicit-declaration-of-function
#include "board.h"
#include "ndeft2t/ndeft2t.h"

/* ------------------------------------------------------------------------- */

#define LOCALE "en" /**< Language used when creating TEXT records. */
#define MIME "nhs31xx/example.ndef" /**< Mime type used when creating MIME records. */

/** The URL will be used in a single-record NDEF message. */
#define MAX_URI_PAYLOAD (254 - NDEFT2T_MSG_OVERHEAD(true, NDEFT2T_URI_RECORD_OVERHEAD(true)))
static const uint8_t sUrl[MAX_URI_PAYLOAD + 1 /* NUL */] = "nxp.com/NTAGSMARTSENSOR";

/**
* The text and the MIME data are always presented together, in a dual-record NDEF message.
* Payload length is split evenly between TEXT and MIME.
*/
#define MAX_TEXT_PAYLOAD (254 - (NDEFT2T_MSG_OVERHEAD(true, \
NDEFT2T_TEXT_RECORD_OVERHEAD(true, sizeof(LOCALE) - 1) + \
NDEFT2T_MIME_RECORD_OVERHEAD(true, sizeof(MIME) - 1)) / 2))
static uint8_t sText[MAX_TEXT_PAYLOAD] = "10 V1-V4";

/** @copydoc MAX_TEXT_PAYLOAD */
#define MAX_MIME_PAYLOAD MAX_TEXT_PAYLOAD
static uint8_t sBytes[MAX_MIME_PAYLOAD] = {0, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE};

/* ------------------------------------------------------------------------- */

/**
* Used to determine which NDEF message must be generated.
* - @c true: generate a single-record NDEF message containing a URL.
* - @c false: generate a dual-record NDEF message containing a TEXT and a MIME record.
*/
static bool sState;

static volatile bool sButtonPressed = false; /** @c true when the WAKEUP button is pressed on the Demo PCB */
static volatile bool sMsgAvailable = false; /** @c true when a new NDEF message has been written by the tag reader. */
static volatile bool sFieldPresent = false; /** @c true when an NFC field is detected and the tag is selected. */

static void GenerateNdef_Url(void);
static void GenerateNdef_TextMime(void);
static void ParseNdef(void);

/* ------------------------------------------------------------------------- */

//Store adc_1, adc_4, current and resistance value
static volatile float adcInput_4 = 5.0; // 4. store V input 4
static volatile float adcInput_1 = 5.0; // 5. store V input 1
static volatile int current_native; // 3. store I2D ana 4
static volatile int current_picoampere; // 3. store I2D ana4
static volatile double resval = -1; // store resistance calculated: (dcInput_1-adcInput_4)/Current_picoampere*10e-6

static void adcdac_nss_example_1(void); //continuous DAC ana1
static void i2d_nss_example_1(void); //I2D ana4
static void adcdac_nss_example_3(void); //NEW single shot get ADC value ana4
static void adcdac_nss_example_3_2(void); //NEW single shot get ADC value ana1


/**
* Handler for PIO0_0 / WAKEUP pin.
* Overrides the WEAK function in the startup module.
*/
void PIO0_IRQHandler(void)
{
Chip_GPIO_ClearInts(NSS_GPIO, 0, 1);
sButtonPressed = true; /* Handled in main loop */
}

/**
* Called under interrupt.
* @see NDEFT2T_FIELD_STATUS_CB
* @see pNdeft2t_FieldStatus_Cb_t
*/
void App_FieldStatusCb(bool status)
{
if (status) {
LED_On(LED_RED);
}
else {
LED_Off(LED_RED);
}
sFieldPresent = status; /* Handled in main loop */
}

/**
* Called under interrupt.
* @see NDEFT2T_MSG_AVAILABLE_CB
* @see pNdeft2t_MsgAvailable_Cb_t
*/
void App_MsgAvailableCb(void)
{
sMsgAvailable = true; /* Handled in main loop */
}

/* ------------------------------------------------------------------------- */

/** Generates a single-record NDEF message containing a URL, and copies it to the NFC shared memory. */
static void GenerateNdef_Url(void)
{
uint8_t instance[NDEFT2T_INSTANCE_SIZE];
uint8_t buffer[NFC_SHARED_MEM_BYTE_SIZE];
NDEFT2T_CREATE_RECORD_INFO_T recordInfo = {.pString = NULL /* don't care */,
.shortRecord = true,
.uriCode = 0x01 /* "http://www." */};
NDEFT2T_CreateMessage(instance, buffer, NFC_SHARED_MEM_BYTE_SIZE, true);
if (NDEFT2T_CreateUriRecord(instance, &recordInfo)) {
if (NDEFT2T_WriteRecordPayload(instance, sUrl, (int)strlen((char *)sUrl))) {
NDEFT2T_CommitRecord(instance);
}
}
NDEFT2T_CommitMessage(instance); /* Copies the generated message to NFC shared memory. */
}

/** Generates a dual-record NDEF message containing a TEXT and a MIME record, and copies it to the NFC shared memory. */
static void GenerateNdef_TextMime(void)
{
uint8_t instance[NDEFT2T_INSTANCE_SIZE];
uint8_t buffer[NFC_SHARED_MEM_BYTE_SIZE];
NDEFT2T_CREATE_RECORD_INFO_T textRecordInfo = {.pString = (uint8_t *)"en" /* language code */,
.shortRecord = true,
.uriCode = 0 /* don't care */};
NDEFT2T_CREATE_RECORD_INFO_T mimeRecordInfo = {.pString = (uint8_t *)MIME /* mime type */,
.shortRecord = true,
.uriCode = 0 /* don't care */};
NDEFT2T_CreateMessage(instance, buffer, NFC_SHARED_MEM_BYTE_SIZE, true);
if (NDEFT2T_CreateTextRecord(instance, &textRecordInfo)) {
if (NDEFT2T_WriteRecordPayload(instance, sText, sizeof(sText) - 1 /* exclude NUL char */)) {
NDEFT2T_CommitRecord(instance);
}
}
if (NDEFT2T_CreateMimeRecord(instance, &mimeRecordInfo)) {
if (NDEFT2T_WriteRecordPayload(instance, sBytes, sizeof(sBytes))) {
NDEFT2T_CommitRecord(instance);
}
}
NDEFT2T_CommitMessage(instance); /* Copies the generated message to NFC shared memory. */
}

/** Parses the NDEF message in the NFC shared memory, and copies the TEXT and MIME payloads. */
static void ParseNdef(void)
{
uint8_t instance[NDEFT2T_INSTANCE_SIZE];
uint8_t buffer[NFC_SHARED_MEM_BYTE_SIZE];
NDEFT2T_PARSE_RECORD_INFO_T recordInfo;
int len = 0;
uint8_t *pData = NULL;

if (NDEFT2T_GetMessage(instance, buffer, NFC_SHARED_MEM_BYTE_SIZE)) {
while (NDEFT2T_GetNextRecord(instance, &recordInfo) != false) {
pData = (uint8_t *)NDEFT2T_GetRecordPayload(instance, &len);
switch (recordInfo.type) {
case NDEFT2T_RECORD_TYPE_TEXT:
if ((size_t)len <= MAX_TEXT_PAYLOAD) {
memcpy(sText, pData, (size_t)len);
memset(sText + len, 0, MAX_TEXT_PAYLOAD - (size_t)len);
}
break;
case NDEFT2T_RECORD_TYPE_MIME:
if ((size_t)len <= MAX_MIME_PAYLOAD) {
memcpy(sBytes, pData, (size_t)len);
memset(sBytes + len, 0, MAX_MIME_PAYLOAD - (size_t)len);
}
break;
default:
/* ignore */
break;
}
}
}
}


// 1. Set the configuration of the analog pins to IOCON_FUNC_1
// 2. Connect the DAC to ANA1, set a continuous conversion of 1.25V.

void adcdac_nss_example_1(void) // Modified IOCON_ANA0_0 --> IOCON_ANA0_1 & ADCDAC_IO_ANA0_0 --> ADCDAC_IO_ANA0_1
{
//! [adcdac_nss_example_1]
Chip_IOCON_SetPinConfig(NSS_IOCON, IOCON_ANA0_1, IOCON_FUNC_1); // IOCON_FUN_1
Chip_ADCDAC_Init(NSS_ADCDAC0);
Chip_ADCDAC_SetMuxDAC(NSS_ADCDAC0, ADCDAC_IO_ANA0_1);
Chip_ADCDAC_SetModeDAC(NSS_ADCDAC0, ADCDAC_CONTINUOUS);
Chip_ADCDAC_WriteOutputDAC(NSS_ADCDAC0, 3000);
//! [adcdac_nss_example_1]
}


/* ------------------------------------------------------------------------- */
// 3. Connect the I2D to ANA4, configure correctly and start a conversion. Only when a conversion is started, current will start flowing over your resistor. The current will continue to flow when the conversion ends. -> a

// FROM i2d_nss_example_1


void i2d_nss_example_1(void)
{
//! [i2d_nss_example_1]
int i2dValue;
int i2dNativeValue;
Chip_IOCON_SetPinConfig(NSS_IOCON, IOCON_ANA0_4, IOCON_FUNC_1); // IOCON_FUN_1
Chip_I2D_Init(NSS_I2D);
Chip_I2D_Setup(NSS_I2D, I2D_SINGLE_SHOT, I2D_SCALER_GAIN_10_1, I2D_CONVERTER_GAIN_LOW, 100);
Chip_I2D_SetMuxInput(NSS_I2D, I2D_INPUT_ANA0_4);
Chip_I2D_Start(NSS_I2D);
while (!(Chip_I2D_ReadStatus(NSS_I2D) & I2D_STATUS_CONVERSION_DONE)) {
; /* wait */
}
i2dNativeValue = Chip_I2D_GetValue(NSS_I2D);
i2dValue = Chip_I2D_NativeToPicoAmpere(i2dNativeValue, I2D_SCALER_GAIN_10_1, I2D_CONVERTER_GAIN_HIGH, 100);
Chip_I2D_DeInit(NSS_I2D);
//! [i2d_nss_example_1]

current_native = i2dNativeValue;
current_picoampere = i2dValue;
}

// 4. Connect the ADC to ANA4, and measure the voltage. -> v4

//FROM Example 3 - Single-shot Analog-to-Digital Conversion without IRQ

// The conversion: adc_input_voltage = (native_value * 1.2V) / 2825 + 0.09V
void adcdac_nss_example_3(void) // Modifications: IOCON_ANA0_5--> IOCON_ANA0_4 & converted adcinput_4= (adcInput_4 * 1.2) / 2825 + 0.09
{
//! [adcdac_nss_example_3]
Chip_IOCON_SetPinConfig(NSS_IOCON, IOCON_ANA0_4, IOCON_FUNC_1);
//Chip_ADCDAC_Init(NSS_ADCDAC0);
Chip_ADCDAC_SetMuxADC(NSS_ADCDAC0, ADCDAC_IO_ANA0_4);
Chip_ADCDAC_SetInputRangeADC(NSS_ADCDAC0, ADCDAC_INPUTRANGE_WIDE);
Chip_ADCDAC_SetModeADC(NSS_ADCDAC0, ADCDAC_SINGLE_SHOT);
Chip_ADCDAC_StartADC(NSS_ADCDAC0);

while (!(Chip_ADCDAC_ReadStatus(NSS_ADCDAC0) & ADCDAC_STATUS_ADC_DONE)) {
; /* Wait until measurement completes. For single-shot mode only! */
}

adcInput_4 = Chip_ADCDAC_GetValueADC(NSS_ADCDAC0);
adcInput_4= (adcInput_4 * 1.2) / 2825 + 0.09; // CONVERSION added line

//! [adcdac_nss_example_3]
}


void adcdac_nss_example_3_2(void) // Modifications: IOCON_ANA0_5--> IOCON_ANA0_1 & converted adcinput_1= (adcInput_1 * 1.2) / 2825 + 0.09
{
//! [adcdac_nss_example_3]
Chip_IOCON_SetPinConfig(NSS_IOCON, IOCON_ANA0_1, IOCON_FUNC_1);
//Chip_ADCDAC_Init(NSS_ADCDAC0);
Chip_ADCDAC_SetMuxADC(NSS_ADCDAC0, ADCDAC_IO_ANA0_1);
Chip_ADCDAC_SetInputRangeADC(NSS_ADCDAC0, ADCDAC_INPUTRANGE_WIDE);
Chip_ADCDAC_SetModeADC(NSS_ADCDAC0, ADCDAC_SINGLE_SHOT);
Chip_ADCDAC_StartADC(NSS_ADCDAC0);

while (!(Chip_ADCDAC_ReadStatus(NSS_ADCDAC0) & ADCDAC_STATUS_ADC_DONE)) {
; /* Wait until measurement completes. For single-shot mode only! */
}

adcInput_1 = Chip_ADCDAC_GetValueADC(NSS_ADCDAC0);
adcInput_1= (adcInput_1 * 1.2) / 2825 + 0.09; // CONVERSION added line

//! [adcdac_nss_example_3]
}







// MAIN
int main(void)
{
Board_Init();
NDEFT2T_Init();
NVIC_EnableIRQ(PIO0_IRQn); /* PIO0_IRQHandler is called when this interrupt fires. */
Chip_GPIO_EnableInt(NSS_GPIO, 0, 1);


// for ever, WHILE field is detected: 2. Connect the DAC to ANA1, set a continuous conversion of 1.25V.
for (;;) {
while (sFieldPresent) {

// 2. Connect the DAC to ANA1 -output Voltage
adcdac_nss_example_1();
// 3. Connect the I2D to ANA4, - read current ana4 through resistor
i2d_nss_example_1();
// 4. Connect the ADC to ANA4, and measure the voltage. ->v4
adcdac_nss_example_3();
// 5. Connect the ADC to ANA1, and measure the voltage. -> v1
adcdac_nss_example_3_2();
// generate the message only once per field???
GenerateNdef_TextMime();
resval = (adcInput_1-adcInput_4)/(current_picoampere * 1e-12); // (v1-v4)/(I4pico * 1e-12) V/I=R [V/A =ohm]
sprintf((char *)sText, "adc_1: %6.2f adc_4: %6.2f current_picoampere: %8.d resistance: %e current_native: %6.d", adcInput_1, adcInput_4,current_picoampere, resval,current_native );//commented in from Thesis, changes payloadText to sText


// attach message to be read
if (sMsgAvailable) {
sMsgAvailable = false;
ParseNdef();
}
}

Chip_PMU_PowerMode_EnterDeepSleep();
}
return 0;

}

Re: NHS3152 - Measure resitance correct param ADC-I2D-DAC

leo94 — Thu, 08 Oct 2020 09:57:10 GMT

Hi @driesmoors,

is there any update on why i am getting erroneous values for Resistance?

I have tested for different resistances (1MOhm, 2Mohm, 3Mohm) and resistance measured is scaling correclty with resitance_real, but still not the correct value.

Best,

Leo

Re: NHS3152 - Measure resitance correct param ADC-I2D-DAC

leo94 — Tue, 03 Nov 2020 16:08:49 GMT

Hi, is there no solution to this problem, or is it out of the scope of this community?

Re: NHS3152 - Measure resitance correct param ADC-I2D-DAC

l95kr — Wed, 10 Nov 2021 09:42:46 GMT

Hi @leo94

I found the error in you code:

when you convert to pA in line 226 you used the Parameter: I2D_CONVERTER_GAIN_HIGH

while having the I2D configuered with the gain low ( Line 219)

I tried it with:

i2dValue = Chip_I2D_NativeToPicoAmpere(i2dNativeValue, I2D_SCALER_GAIN_10_1, I2D_CONVERTER_GAIN_LOW, 100);

and got a resistor Value of rougly 97K using a 100k resistor

Best wishes,

Lennard

Re: NHS3152 - Measure resitance correct param ADC-I2D-DAC

leo94 — Tue, 07 Dec 2021 09:43:45 GMT

@l95kr, thanks!

I just verified it.