WARNING: Not all channels are available in all locales. Please see the 802.11 specs for more information.

A Channels

There are 201 available channels in the 802.11a spec, 0-200. Generally, their frequency in MHz can be found through this equation:

Frequency = 5000 + 5 * (Channel Number)

(from 802.11a 17.3.8.3.2)

In the orginal driver, here are the available channels:

B/G Channels

(from 802.11 15.4.6.2)

Setting a channel

0x2060 Radios

This radio is an 802.11a radio and only uses the 802.11a channels.

1. If the Radar Detection feature is on and the PHY Revision is 3 or greater

   1. Backup the value of RadioRegister 0xC4

   2. Unset bit 0x8000 in RadioRegister 0xC4

2. If the PHY Revision is less than 3

   1. Backup RadioRegister 0x8

3. Write the desired A channel frequency to MMIO offset 0x3F0

4. If the PHY Revision is less than 3

   1. Restore RadioRegister 0x8

5. Write 0x88 to RadioRegister 0x2F

6. Write the RadioRegister 0x2D value specified by the channel to RadioRegister 0x2D

7. MaskSet RadioRegister 0x2E with mask 0x0080 and set with the RadioRegister 0x2E value specified by the channel

8. Using the Frequency Based RadioRegister Value Table Below:

   1. Write 17 * the value to RadioRegister 0x7

   2. Write 17 * the value to RadioRegister 0x20

   3. Write 17 * the value to RadioRegister 0x21

   4. MaskSet RadioRegister 0x22 with mask 0xF and set with 16 * the value

   5. Write 17 * the value to RadioRegister 0x2A

   6. Write 17 * the value to RadioRegister 0x2B

   7. MaskSet RadioRegister 0x8 with mask 0xF0 and set with the value

9. MaskSet RadioRegister 0x29 with mask 0xFF0F and set 0xB0

10. Write 0xAA to RadioRegister 0x35

11. Write 0x85 to RadioRegister 0x36

12. MaskSet RadioRegister 0x3A with mask 0xFF20 and set with the value from the Frequency Based RadioRegister 0x3A table below

13. Mask RadioRegister 0x3D with mask 0xFFC7

14. MaskSet RadioRegister 0x81 with mask 0xFF7F and set 0x80

15. Mask RadioRegister 0x35 with mask 0xFFEF

16. MaskSet RadioRegister 0x35 with mask 0xFFEF and set 0x10

17. Set TX IQ Based On VOS

18. Write the RX IQ Comparison Value for this channel to PHYRegister 0x63

19. Read the value of PHYRegister 0x69

20. Add the TX IQ Comparison Value for this channel to the value of the read PHYRegister shifted right by 8 and clamp the result between [-128, 127]

21. Add the TX IQ Comparison Value for this channel to the value of the read PHYRegister and clamp the result between [-128, 127]

22. Write the the first result left shifted by 8 OR'd with the second result to PHYRegister 0x69

23. If we haven't set the TX power yet, SetTXPower

24. Otherwise, based on the channel frequency

    1. Set RadioRegister 0x17 with the value from the table below

    2. MaskSet RadioRegister 0x19 with mask 0xFF1F and set with the value from the table below

25. If this board has HardwarePowerControl

    1. Set TSSI Power Internal Lookup Table with the current channel

26. If the Radar Detection feature is on and this is an A PHY with PHY Revision 3 or greater

    1. Restore the value of RadioRegister 0xC4

27. Delay for 2000uSec

Frequency Based, RadioRegister Value Table

Frequency Based, RadioRegister 0x3A Value Table

Frequency Based, RadioRegisters 0x17 and 0x19 Value Table

All other Radios

Since all other radios are not 802.11a compatible, we only use the B/G Channels.

1. If the Radio Revision is 8

   1. Back up RadioRegister 0x5C

   2. MaskSet RadioRegister 0x5C with mask 0xF0 and set with 0x5

2. Write the channel frequency in MHz - 2400 to MMIO offset 0x3F0

3. If this is a G PHY

   1. If the country is Japan (We think, it could be a regulatory turn off as Japan allows all frequencies) and the current channel is 14, unset bit 0x80 in SHM offset 0x5E

   2. Otherwise, set bit 0x0080 in SHM offset 0x5E

4. If the channel is set to 14

   1. Set bit 0x0800 in MMIO offset 0x3F4

   2. Set bit 0x0004 in RadioRegister 0x51

5. Otherwise

   1. Mask MMIO offset 0x3F4 with mask 0xF7BF

   2. If this is a B PHY, Mask RadioRegister 0x51 with 0xFFFB

6. Delay 2000uSec
7. If the Radio Revision is 8

   1. Restore RadioRegister 0x5C

We currently don't know what happens if you write other values, so be careful. But probably it'll simply tune to that frequency. I suppose one could try by using something between 2.4 GHz and 2.4835 GHz (see the spec for the actual values depending on the country). We don't know the limits of the chip though, so be careful!