Ryan Malloy
b21f4957f6
Astro 5 + Starlight 0.37 site at site/ with teal/steel theme. Content sourced from 14 reverse engineering docs, master reference, and custom firmware source. Includes Tabs, Badge, Steps, Aside, FileTree, and CardGrid components throughout. DiSEqC SVGs with click-to-zoom via starlight-image-zoom. All internal links validated. Pagefind search indexes all 32 pages.
95 lines
3.4 KiB
Plaintext
95 lines
3.4 KiB
Plaintext
---
|
|
title: RF Specifications
|
|
description: RF input parameters, LNB voltage and current limits, and symbol rate range for the SkyWalker-1.
|
|
---
|
|
|
|
import { Aside } from '@astrojs/starlight/components';
|
|
|
|
## RF Input Parameters
|
|
|
|
| Parameter | Value |
|
|
|-----------|-------|
|
|
| IF frequency range | 950 -- 2150 MHz |
|
|
| Symbol rate | 256 Ksps -- 30 Msps |
|
|
| Input connector | IEC F-type female |
|
|
|
|
The IF frequency is the intermediate frequency after LNB downconversion. The host computes it as `(RF_freq - LO_freq) * multiplier` and sends it in the [TUNE_8PSK](/bcm4500/tuning-protocol/) command payload.
|
|
|
|
## LNB Power Supply
|
|
|
|
| Parameter | Value |
|
|
|-----------|-------|
|
|
| LNB voltage (standard) | 13V / 18V |
|
|
| LNB voltage (boosted) | 14V / 19V (with USE_EXTRA_VOLT) |
|
|
| Maximum continuous current | 450 mA |
|
|
| Maximum burst current | 750 mA |
|
|
|
|
<Aside type="caution" title="Current Limits">
|
|
750 mA is the maximum **non-continuous** (several minutes) allowable load. To avoid overheating the on-board voltage regulator, do not exceed **450 mA** for permanent load. Exceeding these limits may damage the SkyWalker-1 hardware.
|
|
</Aside>
|
|
|
|
LNB voltage is controlled via GPIO P0.4 on all firmware versions. The voltage selection determines the polarization:
|
|
|
|
| wValue | Voltage | GPIO P0.4 | Polarization |
|
|
|--------|---------|-----------|-------------|
|
|
| 0 | 13V | LOW | Vertical / Circular-Right |
|
|
| 1 | 18V | HIGH | Horizontal / Circular-Left |
|
|
|
|
The USE_EXTRA_VOLT command (0x94) enables a +1V boost for long cable runs by toggling bit 3 of the LNB control register at XRAM 0xE0B6 (0x62 = normal, 0x6A = boosted). See [Vendor Commands](/usb/vendor-commands/) for the command interface.
|
|
|
|
## Switch Control
|
|
|
|
The SkyWalker-1 supports multiple satellite switching protocols:
|
|
|
|
| Protocol | Implementation | Command |
|
|
|----------|---------------|---------|
|
|
| 22 kHz tone | GPIO P0.3 gates external oscillator | SET_22KHZ_TONE (0x8C) |
|
|
| Tone Burst (mini DiSEqC) | Timer2-based carrier gating | SEND_DISEQC_COMMAND (0x8D) |
|
|
| DiSEqC 1.0 | Timer2 Manchester encoding | SEND_DISEQC_COMMAND (0x8D) |
|
|
| DiSEqC 1.2 | Timer2 Manchester encoding | SEND_DISEQC_COMMAND (0x8D) |
|
|
| Legacy Dish Network | 7-bit serial bit-bang on P0.4 | SET_DN_SWITCH (0x8F) |
|
|
|
|
## 22 kHz Tone
|
|
|
|
The 22 kHz tone signal is generated by an external oscillator on the PCB, gated by GPIO P0.3. The firmware does not generate the 22 kHz carrier directly -- it only enables or disables the oscillator output.
|
|
|
|
| wValue | State | GPIO P0.3 | Band Selection |
|
|
|--------|-------|-----------|------|
|
|
| 0 | OFF | LOW | Low band (9.75 GHz LO on universal LNB) |
|
|
| 1 | ON | HIGH | High band (10.6 GHz LO on universal LNB) |
|
|
|
|
## Signal Path
|
|
|
|
```
|
|
Satellite
|
|
|
|
|
v
|
|
[ LNB on Dish ] <-- 13V/18V + 22kHz from SkyWalker-1
|
|
|
|
|
| Coax (950-2150 MHz IF)
|
|
v
|
|
[ SkyWalker-1 F-connector ]
|
|
|
|
|
v
|
|
[ BCM4500 Demodulator ] -- demod + FEC decode
|
|
|
|
|
| 8-bit parallel MPEG-2 TS
|
|
v
|
|
[ FX2 GPIF Engine ] -- zero-copy DMA to EP2
|
|
|
|
|
| USB 2.0 High-Speed Bulk
|
|
v
|
|
[ Host PC ]
|
|
```
|
|
|
|
The USB/GPIF data path has substantial headroom over the satellite link throughput:
|
|
|
|
| Metric | Value |
|
|
|--------|-------|
|
|
| USB 2.0 HS bulk (practical) | ~280 Mbps (~35 MB/s) |
|
|
| GPIF engine (theoretical) | 48 MHz x 8 bits = 384 Mbps |
|
|
| Typical DVB-S TS rate | 1--5 MB/s |
|
|
| Maximum symbol rate (30 Msps) | ~58 Mbps |
|
|
|
|
The bottleneck for all supported modulation modes is the satellite link, not the USB data path.
|