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Parity: In serial communications, parity checking refers to the use of parity bits to check that data has been transmitted accurately. The parity bit is added to every data unit (typically seven or eight bits) that is transmitted. The parity bit for each unit is set so that all bytes have either an odd number or an even number of set bits. Refer to the user manual to determine what type of parity is used. In most cases it will be none.
Stop Bits: Stop bits are a way for a computer to "catch its breath" while sending or receiving data, while still letting the other end know that the connection is still there and is still valid; they're also used in error detection. Stop bits are rather like parity bits. They are sent with the data, but they are not part of the data. Unlike parity bits, they are not turned on and off by the number of bits in the data; instead, they are always on. If one or more of the stop bits are missing, it constitutes a framing error. The radios user manual will tell you how many stop bits to use. In most cases it will be 1 or 2.
Handshake Type: This defines the type of “flow control” that is used between the computer and the radio. It allows each of the communicators to signal the other when it has completed an operation and/or ready for more data. If you radio supports flow control, it will be identified in the user manual (Maybe??). If you are unsure about the type of flow control that is used, select NONE. If you are having some difficulty with communications, you might try to use Hardware. Only use the XON/XOFF protocol if the user manual specifically calls for that type of flow control.
Timeout: The time in milliseconds that the radio should respond back to the computer that it has received data and acknowledged that fact that it was received correctly. This value should be set to a value of 1200 milliseconds or less. The software polls the radio every 2000 (2 sec) milliseconds. If the radio has not respond an acknowledgement within 1200 ms there is something wrong. The default for this value is 750, but might need to be increased for some older radios.
Pacing: This is a value in milliseconds. It is a small time delay that is inserted between each character (or byte) that is sent to the radio. Normally this value is 0, but some older Yaesu radios did require this value and should be something less than 12 ms. Yaesu did indicate that a normal value for some of their older radios as 3 – 4 milliseconds.
Write Delay: Some radios (TS-2000 specifically) have trouble with back to back commands that are sent from the computer. The write delay is a small delay that is inserted between commands. A Nominal value will be between 25 – 50 milliseconds.
Retries: When the computer sends data to the radio, it is looking for a return acknowledgement from the radio that the data was acceptable. If the computer does not get that acknowledgement it will retry the data again or error out. The retires value will tell the computer how many times to retry the data before it traps an error. Settings greater than 4 are not really productive.
If you are going to use radios control, make sure the serial cable you use is a good quality cable with good shielding. You are operating this in a RF environment and RF leakage into a serial cable will cause all kinds of problems with the serial data transfer to such an extent that it could not only lockup the radios computer, but your PC as well.
If you are transmitting and notice the frequency, mode or other data coming back from the radio getting jumbled, suspect RFI first before faulting the software. If you do not have any problem with the communications while in the receive mode, then you serial settings are probably set correctly.
Radio Interfacing: Icom radios use a protocol called CI-V,which is an interface that converts the standard 3 wire serial interface to a 2 wire system. Icom provides such an interface until at a price, but there are third party units that will also fit the bill that are cheaper. Building an interface with a few parts is quite simple. Other radios may require an interface unit that will convert the standard RS-232 signals of +/- 12 volts to TTL levels of 0 - 5 volts. Manufactures costs for these units vary, but there are third party units that are considerably less. Rolling your own is also an option.