Talk:Firmware/Serial Terminal

You refer to two XOs with serial ports connected directly? Serial adapters are not used? Wouldn't hurt to mention this. The crossover cable requires two J1 CN24 female connectors and a cable with at least 3 conductors. Connectors available from retail vendors are mentioned in the later section "XO Serial Ports - physical interface". Regards, Peasthope 18:05, 18 August 2012 (UTC)

Thanks. Yes, USB serial adapters are not needed, and won't help, in the XO to XO configuration, but this is not Open Firmware specific, the same can be done with Linux. No, a crossover cable does not require two connectors, it could be fabricated in several ways, depending on what is available. J1 and CN24 are a model-specific identifier, so I would not mention them in the context of software. --Quozl 23:05, 20 August 2012 (UTC)

> No, a crossover cable does not require two connectors, ...

Do you visualize soldering wires directly to the UART? I'd rather make a crossover cable with a connector on each end to plug into Jn on the board; whatever n is for the model in question.

Yes, we have guided people into directly soldering wires to the board for this purpose, but to explain that on the Wiki would be wasteful and too specific to a board revision. I would not recommend making a crossover cable from two of the serial cables, with a Jn connector on each end, because that would require both laptops to be open at the time it was attached ... and involves the loss of two otherwise useful serial cables. Instead, a crossover cable can be fabricated with eight header pins at 2.54mm pitch, in two sets of four pins. But the cable does not require connectors to work, it can be soldered, or twisted together. We cannot know what a remote service person has available, so to specify only certain connectors is an unnecessary restriction. --Quozl 22:03, 18 March 2013 (UTC)

> J1 and CN24 are a model-specific identifier, so I would not mention them in the context of software.

Agreed but a crossover cable is hardware and the software won't work without it and the present description is better but still unclear. What about discussing the crossover connection under "Connecting up" rather than under "Open Firmware".

We don't ship the necessary software tools on Linux to use this mode, so leaving it in an Open Firmware section seems appropriate. --Quozl 22:03, 18 March 2013 (UTC)

> ... the same can be done with Linux.

Typically using an RS232 crossover cable to connect serial ports on two machines. A serial connection directly to a system board would be somewhat unusual. Possible but you'd want to be sure about voltage levels. When connectors are available, as on the XO, they should be used.

I don't think we can be that prescriptive. --Quozl 22:03, 18 March 2013 (UTC)

> [table] A crossover cable consists of the following:
> host pin (cable colour) target pin (cable colour) purpose
> GND (orange) ...

Where do you see these colors? Not on the system board. On the serial adapter? But the premise is that we are not using serial adapters. Shouldn't the table refer to something visible such as conductor numbers in http://wiki.laptop.org/go/File:Closeup-J1.png? Regards, ... Peasthope 01:44, 24 August 2012 (UTC)

These colours are on the serial cable supplied with an OLPC serial adapter. The introduction to the table says that now. I've added connector pin numbers. --Quozl 22:03, 18 March 2013 (UTC)