Post by thread:Production Quality Programmer

Hi Jens, It looks like an interesting circuit - maybe you could give an explanation of how it works - According to Microchip's programming specification Iddp (PIC Current while Programming) is 20 mA and Ipp (Current sunk at _MCLR during Programming) is 50 mA. I'm surprised that an RS-232 port can source this much current. Good work, I'm interesting in learning more about it. myke >I am working on a RS232 powered Production Quality Programmer, look at >http://www.ebar.dtu.dk/~c888600/newpic3.htm. Does anyone like to make / >sell PCB for this programmer? > >Regards, >Jens Dyekjfr Madsen > > "My ancestors didn't spend millions of years clawing their way to the top of the food chain, just so I could become a vegetarian"

Myke Predko <spam_OUTmykeTakeThisOuTPASSPORT.CA> wrote: > >It looks like an interesting circuit - maybe you could give an explanation >of how it works - According to Microchip's programming specification Iddp >(PIC Current while Programming) is 20 mA and Ipp (Current sunk at _MCLR >during Programming) is 50 mA. > >I'm surprised that an RS-232 port can source this much current. > >Good work, I'm interesting in learning more about it. > >>I am working on a RS232 powered Production Quality Programmer, look at >>http://www.ebar.dtu.dk/~c888600/newpic3.htm. Does anyone like to make / >>sell PCB for this programmer? >> >>Regards, >>Jens Dyekjfr Madsen For anyone whose email reader gets a "not found" response on this URL, delete the final stop to give http://www.ebar.dtu.dk/~c888600/newpic3.htm Always a problem when quoting Web addresses, as they are often at the end of sentences (and we get told off for leaving off our full stops, don't we!) As a purely personal viewpoint, however well this works, I wouldn't want to use it because "Gnd" isn't system 0V ground. This means that there are all sorts of problems if you want to test what's going on (have to use scope in differential mode etc). Some years ago I spent ages sorting out why a (high cost commercial) PLD programmer was failing programmed devices on valid test vectors. That programmer drove the "0V/Gnd" IC pin from one of its battery of DACs, relays and analogue switches, and it was an absolute pain getting usable signals. I know I could have floated either the programmer or the scope, but that introduces other problems (including that the floated unit's "ground" can end up at halfway between the mains live and neutral potentials). Where Jens' design will be fine in this respect is where the serial port is on something like a battery-powered laptop or Psion. How about producing positive and negative rails from the three driven input lines, then running a simple dc-dc converter to get +Vpp from the negative rail? I'm sure there's a Maxim or TI part that would suit. Final point while I'm chatting about RS232. Lots of people have referred to Maxim parts. These ARE very good, but don't forget Linear Technology makes a similar range. Pinouts of the LT parts may make PCB layout easier, since they tend to be "side to side" whereas MAX tend to be interleaved. There are differences in other aspects such as Vcc noise generated, RS232 drive voltage when all channels are running at full speed, etc. Tim Forcer .....tmfKILLspam@spam@ecs.soton.ac.uk Department of Electronics & Computer Science The University of Southampton The University is not responsible for my opinions

myke predko wrote: > > Hi Jens, > > It looks like an interesting circuit - maybe you could give an explanation > of how it works - According to Microchip's programming specification Iddp > (PIC Current while Programming) is 20 mA and Ipp (Current sunk at _MCLR > during Programming) is 50 mA. > > I'm surprised that an RS-232 port can source this much current. > > Good work, I'm interesting in learning more about it. > > myke It works just like compic-1. A great explanation can be found at: http://www.ormix.riga.lv/eng/mchip/c1_tech.htm The average of TxD is used to generate Vcc (as PWM): If ADD ax,k1 results in carry then send t1 else send t2 where t1 has n+1 bits high and t2 has n bits high. Data is send as 115200 baud, 8 bit, 1 stop, no parity. Average is (k1/65536+n+1)/10*(V2-V1)+V1. (V2 = -0.7V, V1 = 13.7V). Regards, Jens Dyekjfr Madsen