westaust55
Moderator
Having been recently given a couple of old laptops, I have been thinking about and investigating the possible use of the touchpads with a PICAXE as a form of input device.
The touch pads I have are manufactured by Synaptics. One, a TM41P series device uses a T1004 ASIC together with a PTPM754A microcontroller with trackpoint microcode.. The second has a single T1006 ASIC chip. Seems these touch pads are basically PS2 type devices.
However, research shows that the PS/2 protocol, while in some ways simple, is far too fast for PICAXE BASIC to work with even with a PICAXE operating at 16MHz..Typically PIACXE BASIC command duration is around 250usec at 4MHz whereas clock cycle times are of the order of 60 usec per bit.
The inclusion of a parity bit in the PS/2 data precludes the use of the HSERIN command in the X1 and X2 PICAXE chips. The PS/2 protocol is also a bit like i2c in that each device must be open collector and use of some pull-up resitors to hold the clock and data lines high when neither host or slave device are passing data.
Was about to give up on the possibility of interfacing the touch pads or other PS/2 devices (besides the keyboards for which the PICAXE has in-build code to handle) when I came across a US product from a company AWCE which is basically a pre-programmed PIC chip to act as a PS/2 to RS-232 interface.
See: http://www.awce.com/pak11.htm
As well as inbuilt code to work with PS/2 mice, the chip has the ability to pass control codes directly to the PS2 device and to pass raw data directly through to the RS232 side.
Have sent of an email to AWCE to ascertain a few details including freight costs which is often a killer out of the US.
The touch pads I have are manufactured by Synaptics. One, a TM41P series device uses a T1004 ASIC together with a PTPM754A microcontroller with trackpoint microcode.. The second has a single T1006 ASIC chip. Seems these touch pads are basically PS2 type devices.
However, research shows that the PS/2 protocol, while in some ways simple, is far too fast for PICAXE BASIC to work with even with a PICAXE operating at 16MHz..Typically PIACXE BASIC command duration is around 250usec at 4MHz whereas clock cycle times are of the order of 60 usec per bit.
The inclusion of a parity bit in the PS/2 data precludes the use of the HSERIN command in the X1 and X2 PICAXE chips. The PS/2 protocol is also a bit like i2c in that each device must be open collector and use of some pull-up resitors to hold the clock and data lines high when neither host or slave device are passing data.
Was about to give up on the possibility of interfacing the touch pads or other PS/2 devices (besides the keyboards for which the PICAXE has in-build code to handle) when I came across a US product from a company AWCE which is basically a pre-programmed PIC chip to act as a PS/2 to RS-232 interface.
See: http://www.awce.com/pak11.htm
As well as inbuilt code to work with PS/2 mice, the chip has the ability to pass control codes directly to the PS2 device and to pass raw data directly through to the RS232 side.
Have sent of an email to AWCE to ascertain a few details including freight costs which is often a killer out of the US.
