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IASI-2
Posted by admin on October 26 2008 16:23:06

A major update to the IASI protocol has been released. As a result of feedback from users this new protocol update addresses all of the areas that caused problems particularly in the areas of setting up and multiple devices. The emphasis is now more on automated control rather than manual input from the user via a terminal. All devices start up in the same way regardless of the configuration and all devices must be addresses.

Extended News

A big thank you to all of those who contributed to feedback in order to make this next version much easier to use. The new text protocol makes interfacing devices very easy when using stand alone and in automated systems. This is a firmware change only. The electrical interface remains exactly the same. The improvements / changes are as follows:

1) All of the commands have been reduced form 2 characters to 1 character, this speeds up the interface and also makes it easier to send commands.

2) Configuration settings are NOT remembered and so the ZC configuration settings have been removed that caused the most problems for users. Strangely enough this makes the IASI devices easier to use. There is now a fixed starting point at each reset and it is up to the user to enter any configuration commands needed at start up.

3) Devices now always need addressing but the address is from a fixed 1 byte range (97 to 122) these are printable characters 'a' to 'z' The listen mode, where all devices responded has been removed (see later) and the need for a ':' has been removed. The previous large range of addresses was considered to be overkill, this has been reduced to 25.

4) At reset all devices are configured in invert mode as before, this means that the output from the device (pin 2) is inverted data, acceptable to a standard COM port. A single byte #4 (CTRL-D) can be sent on the bus and all devices will change to non-inverted mode. There is also a command that can change devices individually.

5) There is no fixed baud rate, this is always established at reset up by sending byte #13 (CR) which will select form a fixed range: 9600, 14400, 19200 and 38400

6) There is a new discovery command #1 (CRTL-A). All devices will send back their address and ACK (#62) in an address time slot, these slots are approximately 30ms apart, so a device with address 'a' would send back its address immediately and a device with address 'h' would wait 210ms before sending its address. In this way each device can be discovered by the software with no resulting clashes on the bus.

7) All successful commands send back an acknowledgement (#62), with some exceptions.

The protocol has been designed for the simplest possible data communications both with a terminal, using straight text and also with a microcontroller or PC. There is a fixed set of system commands for all devices and a subset of commands for individual devices.

Just to give an example:

This is a screen shot of BV-Com or any terminal, connected to a matrix display via a COM port, the fist thing done was to press CR a couple of times to establish the Baud rate, this was then followed by CTRL-A, which is non printable and shows up on the picture as a yellow square. The device responds with a>, which is its address followed by the ACK ('>'). The user then typed 'aV' which is the device address followed by system command 'V' (version). The device then responds with '1a>'. The next command am1 'rrrggbbb' is the address followed by the mix command, the result of which are here:

This is the result of the mix command, the device is connected directly to a USB to TTL convertor which supplied the signals and power.