RS-485 Module Updated Schematic Needed

NETMF & Gadgeteer
1

I have purchased the RS-485 Module (PN: RS485-GM-479) to use on a project where I needed to use the auto-direction feature. I used one module at my G400D custom carrier board, and another module at my remote sensor board.

The system worked perfectly when prototyped, so I moved ahead with adding the components to my carrier board and sensor board. But with my new layout, the communications is not working. It seems like I am only getting 3.3V differential even though I have the maxim chip provided with 5V supply. There were two difficulties I had when trying to match the GHI schematic…

1.) There is no part number listed for the actual part that is used on the GHI board for U1 (logic gate chip), so I had to guess on that part. Can anyone tell me what that manufacturer and part number is? I could not see any identifying marks on the IC package.

2.) The schematic provided on the GHI website for the product does not match the components populated on the version 1.1 boards I received. It seems that U2 is missing in version 1.1 (likely because the Maxim chip could accept the 3.3V level input from the G400D module). I did not place the U2 IC on my boards either.

Thanks in advance for any help.

2

@ jar1686 - Welcome to the forum.

We will look into this issue as soon as possible.

1 Like
3

@ jar1686 - The part number for the logic gate is 74LVC1G57. We will be updating the schematic shortly.

1 Like
4

I use that same device on my custom board but I use the simple BSN20 FET level shifting and 5V power to the MAX device. The FET’s are fast enough for the max rate of 115200 that I use.

The TXB range of level shifters from TI are also ideal and work with the MAX device.