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bugmenot
Joined: 31 Dec 2005
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Soutie
Joined: 14 May 2008
Posts: 9
Location: Centurion
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 Posted: Sat 06 Feb 2010 10h06 Post subject: |
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The FT232 is a USB-UART from FTID (ftdichip.com). It allows you to open a virual COM port on your PC over USB. As far as the PC application is concerned it looks and acts the same as a normal COM port.
My first question is why would you want to go back to RS232? Most new PC's don't have RS232 (COM) ports anymore, only USB ports.
Do you have a schematic of the circuit? It should be very simple to replace the FT232 with a max232, just read the data sheets ( http://datasheets.maxim-ic.com/en/ds/MAX220-MAX249.pdf ) and connect the Tx's and Rx's on the logic side of the max device to the same port on the PIC, you will have to make sure you get the directions right. i.e. the pin on the pic that is transmitting should be connected to the input of the 232 (Tin) and the receiving pin of the PIC to the logic output of the 232 converter (Rout).
The 232 pins (Tout and Rin) connect to your PC COM port (usually pins 2 and 3 on a DB9 connector). Don't forget to connect a ground wire from your board to the ground of your PC COM port (usually pin 5 on a DB9 connector).
You will also need to look at your Power supply and check what voltages the PIC is running off, If the PIC is running 3.3V, then you may have an issue with the 5V MAX device if the PIC is not 5V tollerant.
Also I suspect the circuit is USB powered, so If you add a MAX232 you will need to have a separate PSU for the board.
The V+ on the MAX232 is for one of the charge pump caps, connect it to a cap as per the MAX232 datasheet.
If you can send me a schematic of what you plan to build I can see if it will work.
Soutie
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bugmenot
Joined: 31 Dec 2005
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| Posted: Sat 06 Feb 2010 10h49 Post subject: |
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Hey Soutie - thanks for the reply... here are my comments:
[quote="Soutie"]My first question is why would you want to go back to RS232? Most new PC's don't have RS232 (COM) ports anymore, only USB ports.[/quote]
Yep, I agree - the issue for me is that I live in East London so there aren't many options with electronics suppliers and for some reason I can only get my hands on the max232 locally. I can't seem to find the USB ic anywhere around here. I can probably order it but I don't have the inclination to do that right now. My PC does have a serial port.
[quote="Soutie"]Do you have a schematic of the circuit? It should be very simple to replace the FT232 with a max232, just read the data sheets ( http://datasheets.maxim-ic.com/en/ds/MAX220-MAX249.pdf ) and connect the Tx's and Rx's on the logic side of the max device to the same port on the PIC, you will have to make sure you get the directions right. i.e. the pin on the pic that is transmitting should be connected to the input of the 232 (Tin) and the receiving pin of the PIC to the logic output of the 232 converter (Rout).
The 232 pins (Tout and Rin) connect to your PC COM port (usually pins 2 and 3 on a DB9 connector). Don't forget to connect a ground wire from your board to the ground of your PC COM port (usually pin 5 on a DB9 connector).
You will also need to look at your Power supply and check what voltages the PIC is running off, If the PIC is running 3.3V, then you may have an issue with the 5V MAX device if the PIC is not 5V tollerant.
Also I suspect the circuit is USB powered, so If you add a MAX232 you will need to have a separate PSU for the board.
The V+ on the MAX232 is for one of the charge pump caps, connect it to a cap as per the MAX232 datasheet.
If you can send me a schematic of what you plan to build I can see if it will work.
Soutie[/quote]
Thats some good advice - thanks, much appreciated. The Schematic is in pcb format on the one link I provided:
http://czi.uni.cc/wp-content/uploads/2009/09/sd2nandv2.rar
(.rar file - use 7Zip or Winrar to extract).
I am using RimuPCB trial version to view it.
I'm going to give it a go this w/end possibly.
Cheers m8
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bugmenot
Joined: 31 Dec 2005
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| Posted: Sun 07 Feb 2010 18h46 Post subject: |
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The original circuit wasn't ideal because the PIC is a 5v chip and although they were powering the circuit from USB, it was being powered via a regulator at 3.3v (although it seems the PIC is OK with this). The reason for this is because there is an SD card slot and a NAND flash chip which require 3.3v so it was a one size fits all scenario (although (I would have powered the PIC from the 5v side of the USB and the rest on the other side of the regulator.
Anyway, I will be powering the pic and the other units from a seperate psu at the correct voltages (I have an old one from a DVD player with multi outputs - 12, 5, 3.3)
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Soutie
Joined: 14 May 2008
Posts: 9
Location: Centurion
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| Posted: Sat 20 Feb 2010 22h34 Post subject: |
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| Did you ever come right?
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