ADS1291: Waveform issue with ADS1291

yihui zhu

Part Number: ADS1291
Other Parts Discussed in Thread: ADS1292R

hi:

I now use the nordic nrf52832 to debug the ADS1291. Now the problem is that the acquired signal has no QRS waveform. The waveforms drawn by the schematics and acquired data through matlab are as follows. The original data is in the attachment.

1. I referred to the driver of ADS1292R and transplanted the driver code to nrf52832.
www.ti.com/.../TIDM-BIOSIGNMONITOR

2. Now that the register can be read and written correctly, the device ID can be correctly read as 0x52; I am not sure if the register is configured correctly? The values of registers 1 through 11 are configured as follows:
0x02, 0xE0, 0xF0, 0x00, 0x00, 0x23, 0x03, 0x00, 0x02, 0x07, 0x0C
I write these values into registers and read them out to match them. For ADS1291, is my register setting correct? If I want to adjust the parameters, which parameters should I adjust?

3. The conversion mode uses a continuous conversion mode. When entering the DRDY interrupt, 6 bytes of data are read. The ECG status byte is always 0xc00000. This is normal. Will the ECG data read need to be processed? Because it is the type of complement.

What is the processing of the collected data? Can be used to draw waveforms in matlab.Here is my treatment. Is it handled correctly?

Uint32_t u32_SatatusADS1x9xData = 0;
Uint32_t u32_EcgADS1x9xData = 0;
Int32_t tmpdata = 0;

//ECG status data
u32_SatatusADS1x9xData = ((uint32_t)SPI_Rx_buf[0]) << 16;//16~23 bit
u32_SatatusADS1x9xData += ((uint32_t)SPI_Rx_buf[1]) << 8;//8~15 bit
u32_SatatusADS1x9xData += ((uint32_t)SPI_Rx_buf[2]);//0~7 bit

//ECG data
u32_EcgADS1x9xData = ((uint32_t)SPI_Rx_buf[3]) << 16;//16~23 bit
u32_EcgADS1x9xData += ((uint32_t)SPI_Rx_buf[4]) << 8;//8~15 bit
u32_EcgADS1x9xData += ((uint32_t)SPI_Rx_buf[5]);//0~7 bit
The
If( (u32_SatatusADS1x9xData & 0x00f00000) == 0x00c00000)
{
If(u32_EcgADS1x9xData & 0x800000)
{
u32_EcgADS1x9xData ^= 0x8FFFFF;
u32_EcgADS1x9xData += 1;
Tmpdata = (int32_t)u32_EcgADS1x9xData;
Tmpdata = tmpdata * (-1);
}
Else
{
Tmpdata = (int32_t)u32_EcgADS1x9xData;
}
}

4.It is normal for the multimeter to test that the voltage of AVDD is 5V. The voltage of DVDD is about 2.75V. Is this not normal? Because the VDD voltage is 3.3V.

5.I am using a hardware SPI controller configured as follows:

#define NRF_DRV_SPI_ADS1X9X_CONFIG \
{ \
.sck_pin = ADS1X9X_SPI_SCLK_PIN, \
.mosi_pin = ADS1X9X_SPI_SIMO_PIN, \
.miso_pin = ADS1X9X_SPI_SOMI_PIN, \
.ss_pin = ADS1X9X_SPI_CS_PIN, \
.irq_priority = SPI_DEFAULT_CONFIG_IRQ_PRIORITY, \
.orc = 0xFF, \
.frequency = NRF_DRV_SPI_FREQ_500K, \
.mode = NRF_DRV_SPI_MODE_1, \
.bit_order = NRF_DRV_SPI_BIT_ORDER_MSB_FIRST, \
}

5.I have doubts that the reference example uses a clock rate of 1 MHz, but it is not possible on nrf52832. The internal clock is used on nrf52832. why?

6. Is the function ADS1x9x_PowerDown_Enable necessary in the ADS1292R initialization code in the reference design example? as follows：

However, this function is not called in the example in the ADS1292R evaluation board. I have some doubts about this, should I use this function?

void ECGInterface_Init(void)
{

volatile unsigned short Init_i, j;

ADS1x9x_Reset();
for (j = 0; j < DELAY_COUNT; j++)
{
for ( Init_i =0; Init_i < 20000; Init_i++);
for ( Init_i =0; Init_i < 20000; Init_i++);
for ( Init_i =0; Init_i < 20000; Init_i++);
}
Init_ADS1x9x_DRDY_Interrupt();
ADS1x9x_Clock_Select(1); // Set internal clock
for ( Init_i =0; Init_i < 20000; Init_i++);
for ( Init_i =0; Init_i < 20000; Init_i++);
for ( Init_i =0; Init_i < 20000; Init_i++);

ADS1x9x_Disable_Start();// Set START pin to LOW
ADS1x9x_Enable_Start();// Set START pin to High

/* Tie the START pin low to control conversions by command.*/
Hard_Stop_ADS1x9x();// Set START pin to Low

//Why send a start command just to send a stop command.

Start_Data_Conv_Command();
Soft_Stop_ADS1x9x();

for (j = 0; j < DELAY_COUNT; j++)
{
for ( Init_i =0; Init_i < 20000; Init_i++);
}

Stop_Read_Data_Continuous(); // SDATAC command
for (j = 0; j < DELAY_COUNT; j++)
{
for ( Init_i =0; Init_i < 35000; Init_i++);
}
for (j = 0; j < DELAY_COUNT; j++)
{
for ( Init_i =0; Init_i < 35000; Init_i++);
}
ADS1x9x_Read_All_Regs(ADS1x9xRegVal);
ADS1x9x_Default_Reg_Init();
ADS1x9x_Read_All_Regs(ADS1x9xRegVal);

//Put_ADS1x9x_In_Sleep();
ADS1x9x_PowerDown_Enable();
}

Schematic

Fullscreen 2476.raw data.txt Download

Matlab drawn waveform

thinks.

over 7 years ago

0 Alexander Smith over 7 years ago

TI__Guru 55152 points

Hello Yihui,

Welcome to the E2E forum and thank you for your post!

Unfortunately I cannot offer support for the Nordic nrf52832, however will offer support where I can for the ADS1291.

1) Cannot offer support of Nordic device.

2) Registers: these can be reviewed on page 39-49 of the datasheet.
0x02 - CONFIG1 - (Default)
0xE0 - CONFIG2 - Lead off comparators enabled, Reference buffer enabled, otherwise default
0xF0 - Lead off Control Register - Comparator postitive side 70%, Comparator negative side 30%, otherwise default
0x00 - Default
0x00 - Default
0x23 - RLD buffer enabled, RLD connected to IN1N, RLD connected to IN1P, otherwise default
0x03 - Channel 1 lead off detection positive and negative inputs enabled, otherwise default
0x00 - Default
0x02 - Default
0x07 - 64kHz Respiration control frequency, otherwise default
0x0C - Default

3) Yes the data will need to be processed. It is 2's complement binary type and can be converted to either decimal codes or volts as you choose. If the first bit of the data is high then the resulting number is negative, otherwise convert from binary to decimal as normal.

4) DVDD of 2.5V is within the acceptable limit. This can be seen on page 5 of the datasheet.

5) Cannot offer support of Nordic device.

6) Using the power down function is not necessary. Use at your discretion.

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ADS1291: Waveform issue with ADS1291