Working with a em78p447sap....

[TaDa]

Hi!

I'm returning to electronics - and am new to microcontrollers - so please bear with me...

I'm trying to analyse a proprietary board that has a em78p447sap microcontroller and an RF circuit. (Its the head unit for a wireless alarm)

When I work out how it works I would like to change the functions performed by the em78p447sap.

Are they reprogrammable?

If so, what kit would I need?

Thanks!

 

[Number17]

Are they reprogrammable?

A quick look at the datasheet showed that it is OTP, so it can only be programmed once.

 

[TaDa]

Thanks Number17 - I suspected as much - sadly the datasheet was information overkill for me.

I wonder now, is there an easily (and ideally cheaply) re-programmable chip I could use instead?

I suspect that the RF circuit is emitting MHz signals - which are somewhat outside an arduino's capabilities :-(

 

[Number17]

I wonder now, is there an easily (and ideally cheaply) re-programmable chip I could use instead?

I don't know the requirments of the wirless alarm but I guess any general microcontrollers can be used.
Get something like a PIC or AVR whatever you choose. It comes down to personal choice. You would need to buy a programmer, something like a PICKIT2 for PIC's or an AVRdragon for avr.

Atmel Products - Tools & Software
**broken link removed**

Offcourse there is other microcontrollers available, but these are the most common.

I suspect that the RF circuit is emitting MHz signals - which are somewhat outside an arduino's capabilities :-(

Well most RF circuits operate at such high frequencys, but the actual data is send at much slower rates.

 

[TaDa]

Doh! I'd assumed that the oscilator circuit dictated the signal speed. Thinking about it the clock speed of the microcontroller doesn't mean the same thing as the frequency of the signals it can process.

I think I'll go back to my Arduino and see if I can analyse the signal in a better way (arduinoscope may not be fast enough but the arduino itself may be!)

When I have identified the signals and deduced I definitely cannot use an arduino to do my work I'll take a further look at the microcontrollers you suggest.

Thanks for your help

 

[Nigel Goodwin]

Doh! I'd assumed that the oscilator circuit dictated the signal speed. Thinking about it the clock speed of the microcontroller doesn't mean the same thing as the frequency of the signals it can process.

I think I'll go back to my Arduino and see if I can analyse the signal in a better way (arduinoscope may not be fast enough but the arduino itself may be!)

I would imagine it'll be fine, certainly the simple PICKit2 logic analyser would be well up to the task - it's likely to be a serial data train (probably Manchester coded) at a similar speed to 9600baud or (more likely) less.

 

[TaDa]

Hmm! That's interesting. At those speeds I might be able to read it using my pc's serial port - or am I just kidding myself?

The connections connecting RF to microcontroller are marked VCC, GND, DIS and D/O.
Could you tell me what DIS and D/O are?

 

[Nigel Goodwin]

Hmm! That's interesting. At those speeds I might be able to read it using my pc's serial port - or am I just kidding myself?

As it's unlikely to be standard RS232 the PC's UART won't be any help.

The connections connecting RF to microcontroller are marked VCC, GND, DIS and D/O.
Could you tell me what DIS and D/O are?

I would imagine one is going to be bi-directional data, and the other switches between RX and TX.

 

[TaDa]

Thanks!

I'll stick with the arduino then.

I don't know about in/out but I know enough of the circuit to do what I want so I'll stop worrying about it