USB Help & Using the FT4232H Mini Module

ryfitzger227

Hello Everyone.

I'm thinking about purchasing the FT4232H Mini Module for some Serial to USB conversion. It has 4 channels which will allow me to use multiple propellers and maybe some external DB-9 serial ports for a project I'm doing. I'm still learning about the USB connections and I have a few questions I'd like to ask before I go purchasing this thing and experimenting with it.

I'm using schematics for other Parallax boards to help me with this, but I want to see what's required and what's not.

Looking at the datasheet of the FT4232H it seems that I have everything I need to connect the propeller to it and have successful communication.

Channel A Pin Configurations:

16 - TXD
17 - RXD
18 - RTS#
19 - CTS#
21 - DTR#
22 - DSR#
23 - DCD#
24 - RI# / TXDEN*

According to the QuickStart board schematic I leave pins 22, 23, and 24 unconnected. I connect pin 16 to the RX pin on the Propeller (38) and pin 17 to TX on the Prop (37). I'm still a little confused on what I do with pins 18 and 19. Do I leave them unconnected? The QuickStart schematic just had them going to the header I think, for if you needed them. Then I have pin 21 (DTR#) connected to a transistor where the collector is connected to the reset pin on the Propeller. Is this necessary? Could someone explain the purpose of this? The FT4232 uses 3.3V logic instead of 5V, so that's why I'm connecting everything directly to the propeller. Could I just connect the DTR pin directly to the reset pin and forget about the 2n3904?

The only other thing I have a question about is these two other pins - the PWREN# and SUSPEND# pins on the FT4232H. What exactly am I supposed to do with these?

I think I have this figured out for the most part, but someone please confirm that it's this simple. All I need to do is connect the above pins correctly (16-24, and then whatever I need to with the PWREN# and SUSPEND# pins) and I'm okay, right? I want to make sure I don't need resistors, capacitors, etc. in between some of these things. Since I'm using the Mini Module for the FT4232H I don't need to worry about the USB end, just the rs232 end, correct?

Thanks guys for any help. I'm used to just plugging in the quickstart, or using a Prop Plug to communicate - not all this advanced stuff.
- Ryan

P.S.
Here's a DigiKey link if you guys would like more information on the FT4232H Mini Module. http://www.digikey.com/product-detail/en/FT4232H%20MINI%20MODULE/768-1031-ND/2027253

Tracy Allen

Interesting chip.

>>I connect pin 16 to the RX pin on the Propeller (38) and pin 17 to TX on the Prop (37).
That's correct if you want to use the system serial port, logical pins, p30 tx from Prop, and p31 rx input to Prop. You can alternatively use any other pairs of pins on the Prop. Do you plan to use the other 3 FT4232 serial ports, also connected to one Propeller?

>>I'm still a little confused on what I do with pins 18 and 19. Do I leave them unconnected? The QuickStart schematic just had them going to the header I think, for if you needed them.
For most purposes you can ignore them and leave them unconnected. Those are for hardware handshaking with devices that require it.

>>Then I have pin 21 (DTR#) connected to a transistor where the collector is connected to the reset pin on the Propeller. Is this necessary? Could someone explain the purpose of this? The FT4232 uses 3.3V logic instead of 5V, so that's why I'm connecting everything directly to the propeller. Could I just connect the DTR pin directly to the reset pin and forget about the 2n3904?
Your connection to the system serial port p30, p31 allows a computer to program the Prop. A short pulse on the DTR line is necessary to initiate the programming process. Apart from programming, it is often handy to allow means for an external computer to reset the Prop, via the DTR connection. Do not connect DTR directly to RSTn. That would apply a steady level, where it instead needs a low-going pulse. The best combination is a digital transistor that has 10k resistors built in, with a 1nF capacitor in series with the base.

>>The only other thing I have a question about is these two other pins - the PWREN# and SUSPEND# pins on the FT4232H. What exactly am I supposed to do with these?
Are you powering your project from the USB port? Those pins are signals that your system can use to power down when the USB port goes into suspend mode. You can probably ignore them. Note that FTDI does have some good application examples, how to use them.

>>I want to make sure I don't need resistors, capacitors, etc. in between some of these things. Since I'm using the Mini Module for the FT4232H I don't need to worry about the USB end, just the rs232 end, correct?
You might want to take a look at the following thread and suggestion about isolating the FTDI chip, when it is connected to reset the Prop. If either the Prop end or the USB end are disconnected, funny things can happen. Especially if it involves the DTR reset circuit.
Can-Parallax-do-something-about-the-FTDI-reset-bug?

ryfitzger227

Tracy Allen wrote: »

Interesting chip.

>>I connect pin 16 to the RX pin on the Propeller (38) and pin 17 to TX on the Prop (37).
That's correct if you want to use the system serial port, logical pins, p30 tx from Prop, and p31 rx input to Prop. You can alternatively use any other pairs of pins on the Prop. Do you plan to use the other 3 FT4232 serial ports, also connected to one Propeller?

>>I'm still a little confused on what I do with pins 18 and 19. Do I leave them unconnected? The QuickStart schematic just had them going to the header I think, for if you needed them.
For most purposes you can ignore them and leave them unconnected. Those are for hardware handshaking with devices that require it.

>>Then I have pin 21 (DTR#) connected to a transistor where the collector is connected to the reset pin on the Propeller. Is this necessary? Could someone explain the purpose of this? The FT4232 uses 3.3V logic instead of 5V, so that's why I'm connecting everything directly to the propeller. Could I just connect the DTR pin directly to the reset pin and forget about the 2n3904?
Your connection to the system serial port p30, p31 allows a computer to program the Prop. A short pulse on the DTR line is necessary to initiate the programming process. Apart from programming, it is often handy to allow means for an external computer to reset the Prop, via the DTR connection. Do not connect DTR directly to RSTn. That would apply a steady level, where it instead needs a low-going pulse. The best combination is a digital transistor that has 10k resistors built in, with a 1nF capacitor in series with the base.

>>The only other thing I have a question about is these two other pins - the PWREN# and SUSPEND# pins on the FT4232H. What exactly am I supposed to do with these?
Are you powering your project from the USB port? Those pins are signals that your system can use to power down when the USB port goes into suspend mode. You can probably ignore them. Note that FTDI does have some good application examples, how to use them.

>>I want to make sure I don't need resistors, capacitors, etc. in between some of these things. Since I'm using the Mini Module for the FT4232H I don't need to worry about the USB end, just the rs232 end, correct?
You might want to take a look at the following thread and suggestion about isolating the FTDI chip, when it is connected to reset the Prop. If either the Prop end or the USB end are disconnected, funny things can happen. Especially if it involves the DTR reset circuit.
Can-Parallax-do-something-about-the-FTDI-reset-bug?

I thought the same thing. My initial project includes 4 propellers that I'd like to use as 4 separate serial ports. This chip is ideal and it's amazing that I found it (was searching on Google and came across the image!).

I will most likely be connecting the other 3 channels to a Propeller also.

I'm going to be powering my project from the USB port. That's pretty cool that I can reset the prop via the computer. One of the first problems I was having may have a connection with this DTR pin. Before any cogs are started and the program is run, the propeller waits for the computer to send a string of "A". Afterwards, it will send back a string of "B" and start the cogs and run its function. I was having problems with the propeller receiving the first string if it had just been connected to the computer. For example. Using a QuickStart Board, if I would unplug the USB cable from the propeller and then plug it back up to the computer and attempt to send that string of "A" the propeller would not respond. I found that if you attempted to send it a second time the propeller would respond. Now if I reset the propeller and then attempt to send the string from the computer again, the propeller will always respond right back. Since I'm not unplugging the USB cable very often I didn't really worry about it and just programmed something in the VB program to where if it didn't see a response the first time, just try again, and then afterwards display a not found message. I never posted anything on the forums since the vb program fixed it. But now my curiosity is up. Hahaha. Could this be connected with the DTR pin, and if so if I disconnect the DTR pin after programming will it not do this? I'm thinking about putting a 4 position DIP switch on the 4 DTR pins to where I can re program each propeller if the need comes up.

Didn't know you could do so much with the FTDI chip, but I think I'll just ignore the PWREN# and SUSPEND# pins.

The bug shouldn't affect me since I'm powering the board with the USB connection and unplugging it would disconnect all power, thus resetting it anyways.

Please let me know if I'm wrong on anything.

Thanks for the help!
- Ryan