Why is there no output? Why is it not possible to type into the serial port?įor original BeagleBoard, purchase the recommended serial adapter. I have checked that as per the above image, pins are shorted like this: 1-1, 2-2,3-3, 4-4, 5-5 and so on.ĭoes that means my cable is a straight-through cable as required?Īnother resource is here that explains the type of cable I must have: Serial Port-Related The BeagleBoard-xM provides a female DB9 port and requires a serialĬable to connect the console to your host system.
Now this document says that I must have a Straight-through Serial cable. I understand the pins with respect to the following image: I will be using this cable to connect BeagleBoard Xm ver C1 to the serial port of my PC. This cable should work with most serial printers.I have a cable having a DB 9 male at one end and a female at another end. The only RS232 signal used in this cable is the DTR signal which is used by the printer to inform the computer about error situations like out of paper etc. The printer doesn’t send large amounts of data to the attached computer, so there is no need to use handshaking lines on the printer to control the data flow. On the printer side only the data lines and one handshaking line are used.
In that case an RS232 cable is used where some handshaking lines at the PC side are looped back. When a serial printer is connected to a PC with an RS232 cable, the handshaking is not symmetrical any more.
There are cases where disabling all hardware flow control and switching to a simple null modem cable with XON/XOFF handshaking is the only method to successfully connect a serial printer to a computer. Alternatively you might try one of the null modem cables. The wiring diagrams on this page won’t fit to all situations, but you will get your printer connected in at least 95% of the cases. Besides this some printer manufactures decided to use pins not normally used on RS232 interfaces to make the situation even more confusing. Also older serial connected printers often use a mechanical printing method like dot matrix or daisy wheel which speed is limited by the mechanical construction. Think of out-of-paper, off-line or form-feed situations. The printer however has many situations which need handshaking to stop the computer for sending data. Depending on the purpose, sometimes also one or more handshake lines are crosslinked. With a null modem connection the transmit and receive lines are crosslinked. There is no need for the computer to send handshaking signals to the printer. Null modem is a communication method to directly connect two DTEs (computer, terminal, printer, etc.) using an RS-232 serial cable. The main problem of this asymmetric use of RS232 communications is that the handshaking is also not symmetric. It wouldn’t surprise me if most serial printers work without problems if the Tx line of the printer is not connected to the Rx of the computer at all. Although the serial connection is two-way, data is only sent from the computer to the printer. One of these situations is the connection of a serial printer with a computer. However, for some types of communications standard symmetrical null modem cables are not the appropriate solution. Its a shame, a null-modem USB->serial would be a useful gadget. You can completely reprogram the Microchip part, but it will do no good unless the transceiver is rewired too.
For those situations where two DTE devices must be connected directly, null modem cables can be used. It isnt the USB->serial chip thats the problem, but the transceiver chip (e.g., MAX232). The RS232 standard describes the communication between DTE, data terminal equipment (computers, printers, etc.) and DCE, data communication equipment (modems). Introduction to RS232 serial printer cables Texas Instruments 800 and OKIData ML 80 and 90 printer cable.Introduction to RS232 serial printer cables.