Re: TI-H: RE: A86: TI-Network

To: ti-hardware@lists.ticalc.org
Subject: Re: TI-H: RE: A86: TI-Network
From: "ryan pogge" <ryanpogge@hotmail.com>
Date: Thu, 04 Dec 1997 21:55:04 PST
Reply-To: ti-hardware@lists.ticalc.org
wow!
neat.  good luck.

>In that case, no offense, but I'll continue with my own specification 
for the network, as I'd rather see a freeware release.  I figure that 
since these are just calculators (powerful ones, but calculators 
nonetheless), no one should be kept from taking advantage of these 
designs.
>I will elaborate on the general protocol and other aspects right now, 
however.
>Most work will be performed off-board, from one of the Atmel AVR 
microcontrollers.  The system will handle up to 255 (1 reserved for 
"send to all") devices connected, from calculators to expanders and 
possibly other components.  most components will require a special 
"locked burst transfer" mode, in which a device controls the entire bus 
for direct communication, unless compliant drivers are written to access 
these devices.  For example, an expander being run as a standard device 
will be located on the bus, and the communications will be effectively 
locked for other calculators until the expander<->calc transfers are 
complete.
>Error handling will be provided via a 4-bit checksum (sum of bytes, 
separated into "nibbles", readded to crate the 4-bit value), and each 
packet will consist of the following portions:
>
>[startpacket#][destination address][packet x of y][number of data 
bytes][data(up to 4 bytes)][checksum][source address][endpacket#]
>
>startpacket# is a predefined value that defines the beginning of a 
packet, address is the assigned # of the destination device, and I think 
most of the others are self explanatory.
>
>The packets are transmitted cyclically, with "good" packets being 
removed from subsequent cycles.  The retransmit packet is sent as 
follows
>[startreTx#][source address][# of bad packets][bad packet 
#'s][checksum][destination address][endreTx#]
>Where source and destination are the same for each packet type
>
>Excess data is stripped off, and the final, cleaned result is 
transmitted to the calc via the TI protocol (standard TI checksum 
algorithm, etc.), which is ultimately processed by an assembly driver to 
either store the data in mem and edit the VAT appropriately, or use it 
as a returned value in a program.
>
>The first demonstration of this technology will be exposed in a chat 
program, and later, to transmit settings across the whole network for 
demonstration purposes in class.  For example, the teacher can set up a 
graph on one calc, which will subsequently be sent to every student, 
demonstrating the exact data sets needed.  This would be very useful in 
an AP statistics course, which for the most part becomes a calculator 
demonstration class.
>Christopher Kalos
>raptorone@stuytech.com
>Executive Director/Administrator


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