Help with Multi PWM out's

[stocky6409]

Hi All,
Just looking for suggestions/ideas in case others have already done this.
I have need to produce a minimum of 4, more likely 8 and up to a possible 16 INDEPENDANT PWM/analogue outputs for a project. Resolution is *not* of high importance. My current thinking is to use Dallas DS1050 5 Bit PWM controllers - that will give me 8 outputs.
Update frequency for the outputs will be measured in minutes so speed is also not of the essence.
Prob have to use 28 series picaxe - not that I need the IO but have to respond to serial input at anytime while allowing program execution to continue.
Technical, any light at the end of the tunnel for an upgrade of serial routines on the 18 series?
Cheers

Stocky

 

[hippy]

I don't recall that there are any plans to upgrade the 18-range serial routines. With the 18X it is possible to receive one or two bytes in the background and any number providing those are read before any more turn up.

 

[BeanieBots]

When you say an update of minutes, does that mean that you could have very large RC on the output?
If yes, then you could simply set up a five-bit software counter and 'compare' to a number for each output.
If you swap the bits (bit0-5 becomes bit5-0) for the counter, the output ripple will be reduced and the RC will not need to be as large as otherwise expected.

 

[inglewoodpete]

I have used the TLC5620 to provide D-A outputs from a PICAXE. For a good price, the chip provides 4 analogue channels with >256 steady output levels each (no PWM required). All in a 14 pin DIP. It uses bit-banged serial output from the picaxe. There may be I2C equivalents around.

 

[premelec]

I'll second that iPete - I use the 8 channel D/A from TI [-28] with an 08M saves a lot of grief!

 

[stocky6409]

Cheers guys - will have a look at what TI have got