Monthly Archives

November 2007

Serial RS-232

EIA-561

November 16, 2007

Use this pinout with any ethernet cable for RS-232 on RJ45 connectors, courtesy of this blog

 pair     4-pair     RJ-45  color   DB9  DB25  signal  circuit  DTE  DCE
-----------------------------------------------------------------------
1 blue/white 4 red 5 7 SG AB - -
1 white/blue 5 green 2 3 RD BB in out
2 white/orange 3 black 4 20 DTR CD out in
2 orange/white 6 yellow 3 2 TD BA out in
3 white/green 1 blue 9 22 RI CE in out
3 green/white 2 orange 1 8 DCD CF in out
4 white/brown 7 brown 8 5 CTS CB in out
4 brown/white 8 white 7 4 RTS CA out in
- - - - 6 6 DSR CC in out

column legend:
pair = twisted pair number in standard 4-pair cable
4-pair = base/stripe colors in standard 4-pair cable
RJ-45 = pin number
color = wire color on standard RJ-45 connector
DB9 = pin number
DB25 = pin number
signal = EIA signal name (abbreviated form)
circuit = EIA circuit designation
DTE = electrical input or output for Data Terminal Equipment (PC)
DCE = electrical input or output for Data Communications Equipment (modem)
Uncategorized

ADM 9F8 GR Pinout

November 10, 2007

ADM 9F8 GR – rj45 to db9 fem frys part number 2402340

1 – blu
2 – org
3 – blk
4 – red
5 – grn
6 – yel
7 – brn
8 – wht

Uncategorized

OpenBSD 4.2

November 6, 2007

Since I have done some porting for the wireless project this was of particular interest

“Enable interrupt holdoff on sis(4) chips that support it. Significant performance gain for slower CPU devices with sis(4), such as Soekris.” Would you like to tell us more about this?

Chris Kuethe: Quite a number of network adapters have a configurable mechanism to prevent the machine from being run into the ground under network load. This is known as holdoff, mitigation or coalescing. The general idea is that the network adapter does not immediately raise an interrupt as soon as a frame is arrived; rather the interrupt is delayed a short time—usually one frame or a few hundred microseconds—in case another frame might arrive very soon thereafter.

Picking a good delay value, or set of conditions under which to signal the arrival of a frame is not easy. Too much holdoff and network performance is severely degraded, too little and no benefit will be noticed. When ping times go up and TCP stream speeds go down, you’re delaying too much.

In the case of the Soekris (or anything else that uses sis(4)), interrupt holdoff was not enabled. By enabling holdoff, we allow the network controller to delay and buffer a few frames. This spreads cost of the interrupt across several packets.

full story