S2-LP I/Q data GPIO pins

[Levi Mariën]

Posted on February 13, 2018 at 14:49

Hi,

I have a question about the STEVAL-FKI868V1 development kit that is based on the S2-LP sub 1GHz transceiver. We have a system that works at 868MHz and the signal that commes from the system is fed into multiple TI CC1120 transceivers. The transceivers are configured so that the IQ data is outputed on the GPIO pins from the 1-bit Sigma-Delta ADC. The major problem is that the transceiver don't have a lot of documentation on the subject of extracting the IQ data out of the transceiver so we have faced a lot of issues. 

Since we've faced a lot of issues we want to move to other transceivers and looked at the S2-LP transceivers.

In the datasheet we found the following:

The receiver architecture is low-IF conversion, the received RF signal is amplified by a two-stage low-noise amplifier (LNA) and down-converted in quadrature (I and Q) to the intermediate frequency (IF). LNA and IF amplifiers make up the RX front-end (RXFE) and have programmable gain. At IF, the ADCs digitalize the I/Q signals. The demodulated data go to an external MCU either through the 128-byte RX FIFO, readable via SPI, or directly using a programmable GPIO pin.

So therefore the following questions:

1. Is it possible to extract the I/Q data from the S2-LP via the GPIO pins?
2. At what data rate will this data come out?
3. In what format will the data be outputted?

Thank you .

#868-mhz #s2-lp

[Jismal Jamal]

Posted on May 14, 2018 at 16:38

Hello Winfred

Lu.Winfred

Hope you could reply to this‌ thread.

Basically I also do have same question but on a different EVAL board STEVAL-FKI433V2. In my case I need to receive basicOOK/ASK signal from

https://www.maximintegrated.com/en/products/comms/wireless-rf/MAX14html

.

[Winfred LU]

Posted on May 15, 2018 at 05:27

Hi Levi, Jismal,

You are probably looking for S2LP's 'Direct through GPIO mode'.

To receive directly through GPIO, please

1. Configure PCKTCTRL3 register, set RX_MODE to 2
2. Configure GPIO register according to which pin is to be used for data output, for example, GPIO1_CONF
   • set GPIO_MODE to 3
   • set GPIO_SELECT to 8 (RX data output)
3. Measure GPIO1 with a scope for RX data

To transmit directly through GPIO, please

1. Configure PCKTCTRL1, set TXSOURCE to 2
2. Configure GPIO register for which pin to output the clock and which pin to input the data, for example
   1. Configure GPIO2_CONF to output clock to GPIO2
      • set GPIO_MODE to 3
      • set GPIO_SELECT to 4 (TX data internal clock output)
   2. Configure GPIO3_CONF to input data to GPIO3
      • set GPIO_MODE to 1
      • set GPIO_SELECT to 2 (TX data input for direct modulation)
3. Generate data from an external MCU according to the clock
   • TX data are sampled on the rising edge of it
   • To provide a stable input at rising edges, the external MCU may provide (change) data on falling edges
   • Note that packet is managed at micro level. The external MCU is responsible to generate all symbols including Preamble, Sync, and so on

Thank you.

Best Regards,

Winfred