GPIO Pin Map

The Cypress FX2 uses three GPIO ports for hardware control on the SkyWalker-1: Port 0 (IOA), Port 3 (IOD), and Port B (XRAM-mapped IOB). Pin assignments differ significantly between firmware versions due to PCB revisions and design changes.

Pin Assignments Vary By Firmware

The DiSEqC data pin and several LNB control pins changed between firmware versions. Always verify which firmware version is running before driving GPIO pins directly.

Port 0 / Port A (SFR 0x80, IOA)

Stock Firmware

Pin	v2.06	Rev.2 v2.10	v2.13	Notes
P0.0	—	LNB control (0x97)	DiSEqC data	DiSEqC data pin moved across versions
P0.1	Power enable	Power enable	Power enable	BCM4500 power supply enable
P0.2	Power disable	Power disable (init=0x84)	Power disable	BCM4500 power supply disable
P0.3	22 kHz tone	22 kHz tone	22 kHz tone	Gates external 22 kHz oscillator (all versions)
P0.4	LNB 13V/18V	LNB 13V/18V + DiSEqC data	LNB 13V/18V	Also SET_DN_SWITCH bit-bang (all versions)
P0.5	BCM4500 RESET	GPIO status input (0x98)	BCM4500 RESET	Reset and feedback pin
P0.6	—	GPIO control (0x97)	—	LNB control on Rev.2 only
P0.7	DiSEqC data	Streaming indicator	Streaming indicator	DiSEqC data on v2.06 only

Custom v3.01.0

Pin	Custom v3.01.0	Notes
P0.0	—	Unused
P0.1	Power enable	BCM4500 power supply enable (HIGH = on)
P0.2	Power disable	BCM4500 power supply disable (LOW = off)
P0.3	22 kHz tone	Gates external 22 kHz oscillator
P0.4	LNB 13V/18V	Voltage select: LOW = 13V, HIGH = 18V
P0.5	BCM4500 RESET	LOW = reset asserted, HIGH = released
P0.6	—	Unused
P0.7	DiSEqC data + streaming	DiSEqC data (matches v2.06); also streaming indicator

Port 3 / Port D (SFR 0xB0, IOD)

These pins are consistent across all firmware versions:

Pin	Function	Active State	Notes
P3.0	Init HIGH	—	Set during initialization
P3.4	GPIO control	—	Used by Rev.2 FUN_CODE_1fcf
P3.5	TS_EN	LOW	Transport stream enable: LOW = active, HIGH = idle
P3.6	DVB mode	—	BCM4500 mode select; DiSEqC port direction (Rev.2)
P3.7	BCM4500 control	HIGH (idle)	De-asserted (HIGH) when streaming stops

P3.5 During Boot

P3.5 (TS_EN) must remain HIGH (idle) during the boot sequence and demodulator initialization. Driving it LOW before the BCM4500 is fully initialized may produce undefined behavior on the transport stream bus.

Port B (XRAM-mapped IOB)

Port B is used exclusively by the internal debug commands 0x96—0x98. These commands are not used by the Linux or Windows drivers.

v2.06 / v2.13

Pin	Function	Command
IOB.0	GPIO status input	GET_GPIO_STATUS (0x98)
IOB.1	LNB control line 1	SET_GPIO_PINS (0x97)
IOB.2	LNB control line 2	SET_GPIO_PINS (0x97)
IOB.3	LNB GPIO mode	SET_LNB_GPIO_MODE (0x96)
IOB.4	—	Unused

Rev.2 v2.10

Pin	Function	Command
IOB.0	—	Unused
IOB.1	—	Unused
IOB.2	—	Unused
IOB.3	—	Unused
IOB.4	LNB GPIO mode + control	SET_LNB_GPIO_MODE (0x96) + SET_GPIO_PINS (0x97)

Rev.2 moved LNB control from Port B to Port A (P0.6, P0.0).

DiSEqC Data Pin Summary

The DiSEqC data pin assignment is the most significant change between firmware versions. The carrier pin (P0.3) remains constant.

Firmware Version	Data Pin	Carrier Pin
v2.06	P0.7	P0.3
Rev.2 v2.10	P0.4	P0.3
v2.13	P0.0	P0.3
Custom v3.01.0	P0.7	P0.3

The data pin is used only internally by the firmware’s Manchester encoding logic. It controls whether the 22 kHz carrier gate signal (on P0.3) is cut short or held for the full bit period during DiSEqC transmission. See DiSEqC Protocol for the encoding details.

Initial GPIO State

On power-up, the FX2 initialization code sets:

Register	Value	Decode
IOA (P0)	0x84	P0.7=1 (idle), P0.2=1 (power disable active)
IOD (P3)	0xE1	P3.7:5=1 (all control lines idle), P3.0=1
OEA	0xBE	P0.1-5,7 configured as outputs

These initial states ensure:

• The BCM4500 is held in reset (P0.5 driven by output enable, but P0 init has it low after OEA is set)
• The transport stream bus is idle (P3.5 = HIGH)
• The streaming indicator is off (P0.7 = HIGH)
• All BCM4500 control lines are de-asserted (P3.7:5 = 1)

Streaming GPIO State Changes

Pin	SFR	Direction	During Streaming	Streaming Stopped	Function
P0.2	0x80	Output	Set during init	—	BCM4500 config
P0.7	0x80	Output	LOW	HIGH	Streaming status indicator
P3.5	0xB0	Output	Pulsed LOW	HIGH	BCM4500 TS_EN (transport stream enable)
P3.6	0xB0	Output	Controlled	HIGH	BCM4500 DVB mode control
P3.7	0xB0	Output	Controlled	HIGH	BCM4500 control line