Using MAX232 as Serial driver for programming Propeller.
RobotWorkshop
Posts: 2,307
Hello, I have the DIP version of the propeller chip wired up on a protoboard just like the minimal layout shown for the DIP version. It has a 5mhz crystal and 24LC256 DIP. The only difference is that I am trying to use a MAX232 as the level conversion for the Serial Port. The board has a 3.3v regulator for the Propeller and 24LC256. There is also a 5v regulator for the MAX232 and for other options later. It appears that everything is wired up ok but the Propeller chip isn't found by the software. I know the Serial port on the laptop is fine since I can use that to program Stamps and the SX chips with no problems. That leads me back to the MAX232 and how it's wired.
A couple searches found two threads relating to the MAX232 and the reset timing and wiring. I was used to the way it worked on the Stamp and it appears that the action of the DTR on the Propeller is the exact opposite.
http://forums.parallax.com/forums/default.aspx?f=25&m=120725
http://forums.parallax.com/forums/default.aspx?f=25&m=149010&g=149159#m149159
It wasn't clear however that anyone has been able to get the regular 5V MAX232 to work though. If anyone has had success with the MAX232 then perhaps they'll share what worked.
At the moment I have the DB9 connection to the MAX232 wired up the same as I had for the Stamp. This may be contributing to the issue:
From the DB-9 to MAX232:
- DB-9 Pin 2 goes to the banded end of a 1n4148 diode which then goes to pin 7 on the MAX232
- DB-9 Pin 3 goes to the MAX232 pin 8
- DB-9 pin 4 goes to a .1uf cap which then goes to pin 13 on the MAX232.
- DB-9 pin 5 goes to the common ground
- There is a 4.7K ohm resistor across pins 2 and 3 on the DB-9 (like i've used on the stamp)
From the MAX232 to the propeller:
- MAX232 pin 9 goes through a 1K ohm resistor to pin 39 on the Propeller. There is also a 10K pullup to 3.3v on pin 39.
- MAX232 pin 10 goes through a 1K ohm resistor to pin 40 on the Propeller. There is also a 10K pullup to 3.3v on pin 40.
- MAX232 pin 12 goes to a .01uf cap that drives the base of a 2n3904 and also has a 10K pull down to groud.
- The 2n3904 emitter goes to ground and the collector goes to the RESn on the propeller.
I've tried a couple variations on the DTR and reset with no luck.
It's probably just something I keep overlooking and hope that i'll be able to try this out soon.
Robert
A couple searches found two threads relating to the MAX232 and the reset timing and wiring. I was used to the way it worked on the Stamp and it appears that the action of the DTR on the Propeller is the exact opposite.
http://forums.parallax.com/forums/default.aspx?f=25&m=120725
http://forums.parallax.com/forums/default.aspx?f=25&m=149010&g=149159#m149159
It wasn't clear however that anyone has been able to get the regular 5V MAX232 to work though. If anyone has had success with the MAX232 then perhaps they'll share what worked.
At the moment I have the DB9 connection to the MAX232 wired up the same as I had for the Stamp. This may be contributing to the issue:
From the DB-9 to MAX232:
- DB-9 Pin 2 goes to the banded end of a 1n4148 diode which then goes to pin 7 on the MAX232
- DB-9 Pin 3 goes to the MAX232 pin 8
- DB-9 pin 4 goes to a .1uf cap which then goes to pin 13 on the MAX232.
- DB-9 pin 5 goes to the common ground
- There is a 4.7K ohm resistor across pins 2 and 3 on the DB-9 (like i've used on the stamp)
From the MAX232 to the propeller:
- MAX232 pin 9 goes through a 1K ohm resistor to pin 39 on the Propeller. There is also a 10K pullup to 3.3v on pin 39.
- MAX232 pin 10 goes through a 1K ohm resistor to pin 40 on the Propeller. There is also a 10K pullup to 3.3v on pin 40.
- MAX232 pin 12 goes to a .01uf cap that drives the base of a 2n3904 and also has a 10K pull down to groud.
- The 2n3904 emitter goes to ground and the collector goes to the RESn on the propeller.
I've tried a couple variations on the DTR and reset with no luck.
It's probably just something I keep overlooking and hope that i'll be able to try this out soon.
Robert