rs232 input questions

[heepofajeep]

A device I am working on has four analog inputs. I am looking for a way to reliably transfer these inputs to the computer at a reliable speed of no slower than 3.3ms intervals. the voltage range of the analog signals are all 0-20mv.

Also, I would really like to use Labview for this, but the current version of Labview we are using does not allow for this, we can't seem to get the test intervals much below 10ms.

Thanks!

 

[Nigel Goodwin]

Looks like a nice easy job for a PIC?.

 

[erosennin]

Hi heepofajeep,

Take a look at the new 24 series from microchip PIC24FJ128GA in particular. 16Channel 10-bit 500ksps sample rate which is 2ms. Has onboard RS232 and 485.

You might wanna opamp your signals though and then compensate for the gain in the software before it dumps to the PC, you might also have to store a couple values in the ram because of slow transfer speed. If you know VB you can write your own code for a PC program.

datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/39747C.pdf

Hope that helps

p.s. Microchip are quite "liberal" with samples if you know what I mean

 

[Nigel Goodwin]

Hi heepofajeep,

Take a look at the new 24 series from microchip PIC24FJ128GA in particular. 16Channel 10-bit 500ksps sample rate which is 2ms.

500ksps is 2uS, NOT 2mS.

 

[erosennin]

That's even better then isn't it? give's you more coding slack time

 

[heepofajeep]

Thank you for the replies! So where are the best places to buy the PIC, namely the PIC24FJ128GA? Also, because the PIC24FJ128GA is newer, am I going to have any troubles finding tutorials/help for it?

Also, how much [rough estimate is fine] am I looking at cost-wise to buy the PIC24FJ128GA & neccessary interface hardware, and software that would allow me to code this in C/C++.

Thanks!

 

[erosennin]

No need to buy, microchip will sample a couple for free for you worldwide, I'm in australia it takes about 2 weeks for me.

**broken link removed**

Inregards to programs, MPLAB C30, free download (60Day trial) from Microchip website will allow you to code in C, and they have some sample codes etc. available.

**broken link removed**

And here to search for the "Security Bypass".

And its got In system programming so a MAX232 (or similar) on the board and relevent reset buttons will enable you to program the PIC on the board.

 

[heepofajeep]

Awesome! that helps tremendously! What is the security crack needed for? Is that just for when the software expires? Also, is there any output capability of the PIC? Reason I ask is because that would enable me to also drive my stepper motor for the same project...

 

[erosennin]

The pic's got on board PWM, which is part of the capture compare module and you can drive your stepper motor from there with a couple fets etc.

yea, you'll need the crack unless you can finish it in 60Days.

 

[heepofajeep]

The pic's got on board PWM, which is part of the capture compare module and you can drive your stepper motor from there with a couple fets etc.

yea, you'll need the crack unless you can finish it in 60Days.

Actually, I don't even need the PVM, because I am using a driver for the stepper motor, all I need is to be able to output two ttl signals at a reasonable frequency.

 

[mister_e]

All this time i thought it was the way PWM worked

To be honnest, you don't even need to use any 24 series as now 16F or 18Fs are more than capable of. Look for the PIC18F2431 or his big brother PIC18F4431.