AFE4400 for Beginners

SANTU REDDY

Other Parts Discussed in Thread: AFE4400, AFE4400SPO2EVM

Hi ,

I brought AFE4400 for pulse oximeter testing, I read the datasheet and came up with the schematic ( almost similar to application schematic ), I need suggestion on the schematic attached in this post.

I going to use arduino to interface with AFE4400.

I have a doubt whether I can run the AFE4400 with 3.3V only.

I also looking for procedure for troubleshooting AFE4400 ( both hardware and software ).

Also important notes before I should keep in mind while working with AFE4400.

Thanks & Regards,

SRP

over 9 years ago

0 Amy Schnoor over 9 years ago

TI__Mastermind 18275 points

Santu,

We have received your post and hope to have a response back to you soon.

0 Praveen Aroul over 9 years ago

TI__Mastermind 49176 points

Hello SRP,

I have reviewed your schematics. I have the following comments.

1. Depending on the type of LED (green, red or IR) (Vfb of the LED) connected between TXN and TXP and the TX_REF voltage, the LED_DRV_SUP might require to be high as 5V. The datasheet mentions the recommended operating conditions for LED_DRV_SUP (see below)

2. The device can draw high switching currents from LED_DRV_SUP pin. In addition to C7, we also recommend having a bulk cap (atleast 10uF recommended).

3. We also recommend connecting ADC_RDY to an interrupt input pin of the microcontroller.

4. The AFE_PDN pin can be connected to the port pin of the microcontroller.

5. On the VCM pin, connect a series resistor (1 kΩ) and a decoupling capacitor (10 nF) to ground.

The voltage across the capacitor can be used to shield (guard) the INP, INN traces.

6. Layout does impact performance, specifically on the INN/INP and TXN/TXP lines. It is recommended you follow the EVM layout for best performance.

Refer to the following links for any help on AFE4400.

1. AFE4400 sign of life after power-up and reset

http://e2e.ti.com/support/applications/high_reliability/f/30/p/331294/1157075.aspx#1157075

2. AFE44xx SPI communication

http://e2e.ti.com/support/applications/high_reliability/f/30/p/275303/962004.aspx#962004

3. AFE4400 possible initialization sequence

http://e2e.ti.com/support/applications/high_reliability/f/30/p/290393/1013308.aspx#1013308

4. AFE44x0SPO2EVM Message Communication Protocol

http://e2e.ti.com/support/applications/high_reliability/f/30/p/350615/1232995.aspx#1232995

You can also use the community search features located in the top right corner to search for any other help.

0 Sathya Prasad Prabhakar over 9 years ago in reply to Praveen Aroul

Prodigy 85 points

hi,

i am using afe4400 for the first time, only to measure the pulse rate. I wanted to know how can i calculate the heart rate . Is there any formula that i should be implementing in code?? All i know is the output to be read is present in the LED2-ALED2VAL and LED1-ALED1VAL register.

Kindly accept my request and guide me.

Regards,

Sathya

0 Praveen Aroul over 9 years ago in reply to Sathya Prasad Prabhakar

TI__Mastermind 49176 points

Hello Satya,

The photoplethysmogram (PPG) signal from the output of the AFE contains the periodicity of the pulse rate. The number of the peaks refers to the heart rate.

Refer to the following link below to help you get started.

http://e2e.ti.com/support/applications/high_reliability/f/30/p/350615/1238774.aspx#1238774

Unfortunately we do not offer complete software solutions. I recommend that you read some literature on the matter, such as the following book:

http://books.google.com/books?id=XRoEnwEACAAJ&dq=editions:O_-O_AQfFhQC&hl=en&sa=X&ei=JoesU4miLMfsoATYh4GQBQ&ved=0CCEQ6AEwAQ

Regards

Praveen.

0 Sathya Prasad Prabhakar over 9 years ago in reply to Praveen Aroul

Prodigy 85 points

hi,

I am using afe4400 in my project and i am using ubuntu OS. Can anybody provide me wit the driver code for afe4400? My objective is to calculate the number of heart beats per minute.

Thanks and Regards,

Sathya Prasad P

0 Praveen Aroul over 9 years ago in reply to Sathya Prasad Prabhakar

TI__Mastermind 49176 points

Hello Sathya,

The driver code for AFE4400 on an MSP430 platform can be found at the following link: http://www.ti.com/lit/zip/slac678

What is your target platform that is running the Ubuntu OS? The AFE communicates to an external microcontroller or host processor using the serial peripheral interface (SPI).

0 Sathya Prasad Prabhakar over 9 years ago in reply to Praveen Aroul

Prodigy 85 points

Hi Praveen,

I am using wandboard which uses imx6 sololite processor.

Regards,

Sathya Prasad P

0 Praveen Aroul over 9 years ago in reply to Sathya Prasad Prabhakar

TI__Mastermind 49176 points

Hello Sathya,

You can use one of the 2 SPI ports on the EDM connector to interface the AFE to the i.MX6 solo processor.

Unfortunately we don't have the SPI driver for the i.MX6 processor.

0 Sathya Prasad Prabhakar over 9 years ago in reply to Praveen Aroul

Prodigy 85 points

Hi Praveen,

Yes i will interface through SPI. and the driver code which you provided is a ".exe" file so i am not able to open in ubuntu. What type of value can I expect in the output registers?? I am really confused as to how to get the number of heart beats per minute.

Thax and Regards,

Sathya Prasad P

0 Praveen Aroul over 9 years ago in reply to Sathya Prasad Prabhakar

TI__Mastermind 49176 points

Hello Sathya,

The driver code is provided with a software license agreement and when you run the executable, you will need to accept the SLA to continue with the installation.

Unfortunately the driver code is only available as a Windows Installer. We do not support other OS platforms.

Please follow the FAQ section (question # 18) in the link below to get an understanding on how to get HR data from the ADC output.

http://e2e.ti.com/support/applications/high_reliability/f/30/t/369445.aspx

Best regards.

0 Sathya Prasad Prabhakar over 9 years ago in reply to Praveen Aroul

Prodigy 85 points

Hello Praveen,

I would like to go through the software license agreement. Also i would like to know what kind of sgreement are we getting into . So Can you please let me know the details regarding the software license agreement?

Thanks and regards,

Sathya Prasad P

0 Praveen Aroul over 9 years ago in reply to Sathya Prasad Prabhakar

TI__Mastermind 49176 points

Hello Sathya,

PFA SLA.

1727.AFE44xx Source Code License.pdf

Regards

Praveen.

0 Sathya Prasad Prabhakar over 9 years ago in reply to Praveen Aroul

Prodigy 85 points

hi Praveen,

Thank you for providing me the pdf. I am not able to figure out what type of output signal we will get in those output registers of afe4400. Can you please guide me on that.

Regards,

Sathya Prasad P

0 Praveen Aroul over 9 years ago in reply to Sathya Prasad Prabhakar

TI__Mastermind 49176 points

Hello Sathya,

The AFE4400 ADC output registers contains the Photoplethysmogram (PPG) signal corresponding to the LEDs and ambient signal. Please refer to the AFE4400 datasheet for more details on the registers.

The PPG signal comprises of a pulsatile signal riding on top of a DC level. The strength of the pulsatile signal is representative of the modulation in the light intensity because of the pulsatile nature of the arterial blood, while the DC level is a measure of the light amplitude from all time-invariant components (like tissue, venous blood, etc).

Best Regards

Praveen.

0 gladys jessica over 9 years ago in reply to Praveen Aroul

Prodigy 10 points

I agree, it works fine for me.. the PPG reports what it needs to report, there are a lot of intricacies to the circulatory system.

0 Sathya Prasad Prabhakar over 9 years ago in reply to Praveen Aroul

Prodigy 85 points

Hello Praveen,
Once the data in the adc is converted then the adc_rdy signal is triggered. So at the controller side we can check for adc_rdy signal. But is there a possibility to know if the adc_rdy signal is triggered at the afe4400 register level.

Regards,
Sathya Prasad P

0 Praveen Aroul over 9 years ago in reply to Sathya Prasad Prabhakar

TI__Mastermind 49176 points

Hello Sathya,

No, the trigger of the adc_rdy signal is not captured at the AFE4400 register level.

Regards
Praveen.

0 Sathya Prasad Prabhakar over 9 years ago in reply to Praveen Aroul

Prodigy 85 points

Hi Praveen,
I was going through the spi interfacing for afe4400. I know that there are 4 spi-modes. And if im not wrong in the data sheet it shows that the data is latched on the rising edge of the clock. So I came to a conclusion that it uses SPI_MODE_0 (i.e. CPOL=0 and CPHA=0) . But in another post ( http://e2e.ti.com/support/applications/high_reliability/f/30/p/273506/955172#955172) u have mentioned to set it for CPOL=0 and CPHA=1 which is the SPI_MODE_1. Can you please clarify this doubt for me.

Regards,
Sathya Prasad P

0 Praveen Aroul over 9 years ago in reply to Sathya Prasad Prabhakar

TI__Mastermind 49176 points

Hello Sathya,

AFE4400 EVM uses MSP430 microcontroller for data capture and processing.
Below is the serial clock phase and polarity settings for the serial interface of the MSP430.

/cfs-file/__key/communityserver-discussions-components-files/73/1882.USCI_5F00_.png

The clock polarity and phase settings that I mentioned in the thread was based on this.

0 Likhitha Neelisetty over 8 years ago in reply to Praveen Aroul

Prodigy 100 points

Hi,

When i try to open AFE44x0SPO2EVM GUI it says that an error occured while communicating with the device. The Evaluation board is connected to my PC and the driver is installed. Can anyone please help me out.

Regards,
Likhitha

0 Amy Schnoor over 8 years ago in reply to Likhitha Neelisetty

TI__Mastermind 18275 points

Likhitha,

Have you tried updating the firmware without the GUI?

0 Likhitha Neelisetty over 8 years ago in reply to Amy Schnoor

Prodigy 100 points

Hi Amy Schnoor,

Can you please guide me as how to do that? I am not able to update firmware through GUI.

Regards,
Likhitha

0 Likhitha Neelisetty over 8 years ago in reply to Likhitha Neelisetty

Prodigy 100 points

Hi Amy,

If you are talking about the firmware available on TI site (AFE4400SPO2EVM Firmware Source v1.3) , yes i ran it.

0 Likhitha Neelisetty over 8 years ago in reply to Likhitha Neelisetty

Prodigy 100 points

Hi,

I am using windows 8.1 and the driver of AFE4400SPO2EVM shows uninstalled (bang is seen in Device manager).
I followed steps provided in user guide to disable driver signature enforcement and I don't find any warning message to install the driver after I restart my PC. Driver did not get installed.
I also tried disabling the secure reboot and followed steps to disable driver signature enforcement through advanced start up settings and also through command prompt using command
bcdedit .exe -set loadoptions DDISABLE_INTEGRITY_CHECKS
( www.isunshare.com/.../how-to-disable-or-enable-driver-signature-enforcement-in-windows-8-and-8.1.html)
This did not work too.
Can you please tell me if there is AFE4400 EVM secure driver available for windows 8.1 or is there any work around?

Regards
Likhitha

0 Amy Schnoor over 8 years ago in reply to Likhitha Neelisetty

TI__Mastermind 18275 points

Likhitha,

OK. This does not sound like a FW revision problem. Could you send me a screen shot of your device manager when you plug in the EVM? I want to see what the port shows up as.

0 Likhitha Neelisetty over 8 years ago in reply to Amy Schnoor

Prodigy 100 points

Hi Amy,
It worked after changing NTamd64 to NTamd64.6.3 in AFE44X0.inf and repeating process of disabling driver signature enforcement.
Thank you for your support..

Regards
Likhitha

0 Amy Schnoor over 8 years ago in reply to Likhitha Neelisetty

TI__Mastermind 18275 points

Likhitha,

Glad you were able to solve the problem and appreciate you posting your solution.

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AFE4400 for Beginners