USB on the GO hardware

[ipavelek]

Hi my name is Israel Pavelek I´m from Argentina and I´m developing a product that need a conection to a pc and to a pendrive they don´t have to be simultaneous, I was first of all thinking in the MCF51JM128 because the aplication do not need a more than a couple of pins for conectt a graphical 128*64 LCD and a serial conection from a other microcontroller that give the information to the LCD, I would like to have both conectors the B for the PC and A for the pendrive to download a couple of data, If there any problem if someone plug the pendrive in the A conecctor and the pc in B coneector at the same time? the other problem is how to connect them, I saw that the USB hardware connections use two chips adm869L and max3353 are they totaly necesary? what are the purpose of them? because a can´t find them in Argentina, besides i´m thinking first of all to develop with a DEMOJM kit.

A distributor in Argentina offer me the MCF52259 demo kit also, i´m not now working with ethernet.. the USB part it´s the same? I´m talking about the software and hardware.

Thanks
Israel Pavelek

[kef]

Welcome to the forum, Pavelek

I'm also considering using OTG feature of MCF51JM or maybe MCF5225x. I'm also going to use standard size B connector for PC connection and standard A connector to connect flash drive. I'm not very familiar with USB, because I have used only FTDI chips.

Yes, PC and flash drive shouldn't be inserted simultaneously. My board won't be powered from USB. I'm going to detect if 5V power from PC is present, and if present, then power from type A socket (flash drive) will be immediately removed. I don't expect very much that unpowered flash drive won't disturb PC connection, but at least nothing will smoke.

ADM869L is high side switch, which switches power to flash drive. You can use any other chip for this, or maybe even simple FET solution. MAX3353 is more useful for 3V powered designs. Flash drive should be powered from 5V and MAX3353 allows to step up voltage to 5V. Second function of MAX3353 is on/off control of device mode pull-up resistor and on/off control of host mode pull-down resistors. Host mode pull-down 15kOhm resistos can be controlled directly from JM I/O pins. You need to wire one 15K end to USBD? pin, another end to JM I/O pin. To disable 15kOhm pull-down set up I/O pin direction to input. To enable 15k pull-down set direction to output and set output pin low.  Device mode pull up resistor can be controlled in the similar way if JM is powered from 5V. Or, I think it can be controlled automatically from 5V power from B connector. PC not connected - USB pin not pulled up.

[ipavelek]

Hi. my name is Israel Pavelek from Argentina, I would like to have in my proyect the capability of plug a pendrive or plug to the computer, without changing any jumper, so it would be transparent for the user. Let see if I can explain it better. My proyect has an LCD display if the user conects in the A USB port a pendrive, he can be capable of download the image to the pendrive, but if he plug into the mini A-B to the computer connector he would be able to download the image to the computer directily, without changing any jumper, It´s that posible,How can a change from Device to Host, how can i detect these situations? when someone plug a Pendrive or a Mini to pc cable. ? And the critial how to prevent that the user plugs both de pendrive  into the A port and the pc into de MIni a-b port?

Thanks

Israel Pavelek