AFE4490 interface with CC2541.

cherry maskara

Other Parts Discussed in Thread: AFE4490, CC2541

Hello,

I am trying to interface AFE4490 with CC2541. I have my own AFE4490 breakout board and I am using CC2541 Keyfob for testing it. I am able to read and write the registers of AFE4490. That means SPI is working well( I am using alternate 1 location of CC2541 for SPI). I have also checked voltages on following pins and they almost satisfy the requirements for AFE to be working-

TX-REF = 0.68V

BG = 0.97V

VCM = 0.91V.

I am using 3.3v for all voltage supplies (even for LED supplies).

In my main code I have configured all the registers by writing appropriate values to it. After the writing is done the LED's of the probe is lighting up and it remains ON.

But my main purpose is to send the data via bluetooth to a PC. For this I modified the code of SimpleBLEPeripheral and initialized the SPI settings and register settings in SimpleBLEPeripheral_Init() function of SimpleBLEPeripheral.c. Just after programming the Keyfob, the probe's LED lights up for a few seconds and then goes OFF. I am unable to figure out where the problem lies.

Please help!

over 9 years ago

0 Praveen Aroul over 9 years ago

TI__Mastermind 49986 points

Hi Cherry,

We have received your inquiry regarding the AFE4490 and hope to have some answers back to you shortly.

0 cherry maskara over 9 years ago in reply to Praveen Aroul

Prodigy 150 points

Hi,

Thank you for your response. I also have some doubts regarding RESET pin of AFE4490. When the AFE is powered up, the voltage on RESET pin appears to be 3.05V although the RESET pin is not pulled up high in my schematic. When RESET pin is applied a low going pulse, the probe LED stops lighting up. In fact if I apply any voltage on RESET pin(either high or low), probe LED does not light up. It only lights up when I program using the four SPI pins and AFE-PDNZ is pulled high. I wonder why this is happening because in the datasheet it is mentioned that the registers must be initialized to default values. But as soon as I set the direction of my microcontroller pin, which is connected to RESET, as output, the probe LED goes off.

I tried to interface AFE4490 breakout with MSP430 and it worked fine. But I am facing these problems with CC2541. Please help me with this and the bluetooth code as previously mentioned. I am running out of my project submission dates!!

0 cherry maskara over 9 years ago in reply to cherry maskara

Prodigy 150 points

Hi,

My code is working!!! I am able to receive pulse data from AFE4490 via bluetooth. I pulled up AFE_PDNZ pin by connecting it to 3.3v (hardwiring). But I am still confused about the RESET pin. I have not used it in my initialization and have left the pin unconnected. My conclusions do not go according to the datasheet so I am still confused. Please help!!

0 Lakeishia Brown over 9 years ago in reply to cherry maskara

TI__Prodigy 230 points

Hi Cherry,

There is an internal 100k pull-up resistor at the RESETZ pin in AFE4490.

Best Regards,
Lakeishia Brown

0 cherry maskara over 9 years ago in reply to Lakeishia Brown

Prodigy 150 points

Hi Lakeishia,

Thank you for your response. I have been able to successfully interface the AFE4490 breakout board. Now I have soldered AFE in my own custom board. But I am facing certain problems. My RX and LED supplies are of 3.3v. The AFE is responding well i.e. there are appropriate voltages on TX_REF, BG and VCM pins. I observe 4 MHz clock on CLKOUT pin. The SPI communication is also working well. But I am not getting any waveform on TXN and TXP pins. I measure the voltages on the TXP and TXN pins to be 3.3v and 0v respectively.

Please help me resolve this problem.

0 Lakeishia Brown over 9 years ago in reply to cherry maskara

TI__Prodigy 230 points

Hi Cherry,

Do you have your TXN and TXP pins connected to the sensor?

Best Regards,

Lakeishia

0 cherry maskara over 9 years ago in reply to Lakeishia Brown

Prodigy 150 points

I am using the probe provided with the AFE4490 evaluation kit. The probe contains a DB-9 connector, so my connections are as follows.

0 Lakeishia Brown over 9 years ago in reply to cherry maskara

TI__Prodigy 230 points

Hi Cherry,

What waveforms are you expecting to see on the TXN and TXP pins?

When you connect the sensor board to your custom board, do the LEDs on the sensor board turn on?

Regards,

Lakeishia

0 Praveen Aroul over 9 years ago in reply to cherry maskara

TI__Mastermind 49986 points

Hi Cherry,

The DB-9 sensor cable connections are not correct.

Pin #2 should be TXP

Pin #3 should be TXN

Pin # 7 should be cable shield / GND.

0 cherry maskara over 9 years ago in reply to Praveen Aroul

Prodigy 150 points

Hi Praveen,

Thanks for the quick response. I actually posted the connection of the female connector on the board by mistake, so according to that, the connections are correct.

0 cherry maskara over 9 years ago in reply to Lakeishia Brown

Prodigy 150 points

Hi Lakeishia,

According to the following link, AFE4490 must have waveforms on the TXN and TXP pins (page 38).

www.ti.com/.../slau480c.pdf

When connecting the probe, the LED is not lighting up, nor am I being able to receive any input on INX and INP pins if I externally power the LED of the probe.

Thanks,

Cherry

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AFE4490 interface with CC2541.