The following signals are necessary for RX direct mode
RX data clock output
RX data output
You can assign them to any radio GPIO pin by setting the corresponding GPIO_MODE to RX_DATA_CLK or RX_DATA via the GPIO_PIN_CFG command.
The following signals are necessary for TX direct mode
TX data clock output
You can assign it to any radio GPIO pin by setting the corresponding GPIO_MODE to TX_DATA_CLK via the GPIO_PIN_CFG command.
TX data input
The TX_DIRECT_MODE_GPIO field of the MODEM_MOD_TYPE property determines which radio GPIO pin is selected as the modulation data source during TX Direct mode. Also the GPIO_MODE of the corresponding radio GPIO has to be set to INPUT via the GPIO_PIN_CFG command.
When generating the configuration from WDS, GPIO mode can be selected on the "GPIO and FRR" tab of the configurator. However the TX_DIRECT_MODE_GPIO field is left by WDS always in the default GPIO0 setting and can be modified only by hand in the generated config header.
Note 1: For Si4x55 the TX data input can be assigned only to GPIO0.
Note 2: For active signals like data and clock, the GPIO0 and GPIO1 pins should be primarily used , because these have less susceptibility to generating spurious components in the synthesizer than GPIO2 and GPIO3 have.
How can I make the frequency bandwidth of PCB antennas wider?
In some cases/applications the BW of printed antennas might not be sufficient. This article summarizes some design tricks on how to make a printed antenna wider bandwidth.
- Increase the board size (e.g. GND plane in the case of monopole-type antennas). Avoid using RF modules that have smaller size than quater-wavelength. Small modules generally have poor antenna gain and narrow bandwidth (due to the high Q factor).
- Increase the board thickness. Of course, it's typically limited by design.
- Decrease the dielectric constant of the PCB. Select PCB material with low epsilon value.
- Use wider and/or tapered traces in the PCB antenna structure.
- Do some tricks in the external antenna matching network. I.e. use more components to do the match (to stay within a given constant Q ellipse on the Smith Chart); create resonators in the matching network. Also, see Bode-Fano, Youla matching techniques.
The PART and ROMID reply fields of the PART_INFO command are sufficient to identify EZRadio/PRO part number and revision according to the following table.
How should I route the traces on more-layer RF designs for optimal performance?
In order to achieve the possible best RF radiated performance the followings are suggested for more-layer RF board designs:
- Top Layer: Components and short traces. Top layer should use as large and continuous GND plane metallization as possible (with many stitching GND vias) on the entire PCB.
- 1st inner layer: GND plane and traces if necessary. The most important rule is to keep the GND pour metallization unbroken beneath the RF areas (between the antenna, matching network and RF chip). Traces can be routed under the non-RF areas and use GND pour where possible.
- 2nd, 3rd... inner layers: Traces. VDD and all other traces are suggested to be routed on these layers. Use GND pour where possible.
- Bottom Layer: GND plane. Use as large and continuous GND plane as possible. Do not route traces on this layer, just if it is necessary, e.g. short connection traces to connectors.
- Generic for each layer: Try to avoid routing traces along or close to the board edges. It is recommended to place ground stitching vias with GND pour along the PCB edges.