I need to make serial connection between regular PCs and a 3.3v TTL device, I using the Maxim 233 which has internal capacitors.
I have the PCs incoming TD connected to R1_IN and RD T1_OUT. The ground pin5 is connected to the frame ground as well and its connected to the maxim233s GND.
What is unique in my setup that I running this chip from 3.3V instead of 5V because if I run it from 5V it will give out 5V on its low ttl part and can hurt the micro.
The outgoing data from the device to the PC works.
The incoming data from the PC to the device does not.
I can measure -10V if I check on the GND and the incoming wire.
Any ideas how to debug this any further? All the connections are triple checked and if it works one way there must be some minor issue. I use the same 9600 baud data rate for all tests on both ends. I have tried to replace the chip just in case that didn't solve anything.