Hi
I'm working on a project involving an outdoor solar powered device that I want to interrogate remotely from a PC, both to download control data and retrieve instrumentation. A wired connection is not possible - but a wireless link of maybe 20-30 metres would do the job.
I have a prototyped device which has a single data line presenting an analogue voltage representing a measurement - six address lines allow the desired measure to be selected (using analog multiplexors to switch), and will need to add some sort of AtoD conversion before transmission - 8-bit should be adequate.
I am unsure as to the best approach to provide the remote wireless link. I have been wondering about ...
(a) buying a wireless LAN card, which will talk to an IP wireless network and present an RS232 interface to the electronics (a bit nervous about the current load from this though - might need to trigger it with a separate low current receiver rather than leaving it permanently active). And I've never worked with the electronics side of RS232 either though from reading the web, it doesn't look too hard.
(b) using two matched pairs of AM or FM transmitter/receivers on the 433 Mhz bands, that effectively links a single data-line in each direction, with an arrangement of shift registers and logic to awaken the transmitter and send a sequence of all metrics over the link when triggered
(c) same as (b) but using UARTS for the encoding / decoding
(d) using a PIC processor to provide/control the link, either totally in software, or with some help from external logic. The PIC would be powered up when the receiver received a trigger rather than running all the time.
I can envisage how all of these would be possible - however, while I'm comfortable with basic electronics, TTL/CMOS logic, op-amps and such, I've never worked with serial links or UARTS before. Neither have I used a PIC before, though I'm fluent with programming in assembler and C/C++ so confident that I could learn to program a PIC easily enough.
But, I would like to pick the best approach at the first attempt and am unsure. Can anyone out there offer some ideas as to how I should choose between them (e.g. any pitfalls I should be aware of), or suggest any other alternatives.
By the way, this device is solar powered, and working off a float-charged 6V lead acid battery - only a small panel so on a tight energy budget.
Any thoughts/ideas?
I'm working on a project involving an outdoor solar powered device that I want to interrogate remotely from a PC, both to download control data and retrieve instrumentation. A wired connection is not possible - but a wireless link of maybe 20-30 metres would do the job.
I have a prototyped device which has a single data line presenting an analogue voltage representing a measurement - six address lines allow the desired measure to be selected (using analog multiplexors to switch), and will need to add some sort of AtoD conversion before transmission - 8-bit should be adequate.
I am unsure as to the best approach to provide the remote wireless link. I have been wondering about ...
(a) buying a wireless LAN card, which will talk to an IP wireless network and present an RS232 interface to the electronics (a bit nervous about the current load from this though - might need to trigger it with a separate low current receiver rather than leaving it permanently active). And I've never worked with the electronics side of RS232 either though from reading the web, it doesn't look too hard.
(b) using two matched pairs of AM or FM transmitter/receivers on the 433 Mhz bands, that effectively links a single data-line in each direction, with an arrangement of shift registers and logic to awaken the transmitter and send a sequence of all metrics over the link when triggered
(c) same as (b) but using UARTS for the encoding / decoding
(d) using a PIC processor to provide/control the link, either totally in software, or with some help from external logic. The PIC would be powered up when the receiver received a trigger rather than running all the time.
I can envisage how all of these would be possible - however, while I'm comfortable with basic electronics, TTL/CMOS logic, op-amps and such, I've never worked with serial links or UARTS before. Neither have I used a PIC before, though I'm fluent with programming in assembler and C/C++ so confident that I could learn to program a PIC easily enough.
But, I would like to pick the best approach at the first attempt and am unsure. Can anyone out there offer some ideas as to how I should choose between them (e.g. any pitfalls I should be aware of), or suggest any other alternatives.
By the way, this device is solar powered, and working off a float-charged 6V lead acid battery - only a small panel so on a tight energy budget.
Any thoughts/ideas?