Night Rider
Member
A few weeks ago i had post a problem that i had, trying to make RF connection with 2 Pic controllers and rr3 and rt4 modules of telecontrolli. Nigel said me to transmit with manchester, because it is not dc couple. Alright. But i also was transmiting with pcm and i had problem to the receiver. i couldn't detect the frame that i was transmiting. I don't use the USART module as the uC's i use for the experiment are the pic16f84a(transmitter) and 12f675(receiver). So, i made the protocol. Before i talk for the protocol, i must say that i though to try to see if the connection is ok without the rr3 and rt4, only with a cable between the 2 uC's. I connect them from the RA1 of f84a to GPIO2 of f675. i use the external interupt of GPIO2 with the internal pull-up-->ON. My protocol goes like this: LOW(2msec) for start bit, 8 bit of 600us each for data and LOW(1msec) for stop bit. I have 2 LED's at the 12f675 to show me if there is an error or the connection is done. I saw that the connection didn't work, because the error LED always was ON when i was transmiting and i try to test something simple. I kept for transmission only the start bit(2msec). When i transmit, the external interupt at 12f675 goes to a routine which scan for 1,87msec the status of GPIO2. The start bit from the transmiter 16f84a is 2msec LOW. if the status is LOW during the 1,87msec scanning, at the end of 1,87msec the LED of good reception is ON. But this never happened. Always the error LED is ON. This show me that the start bit isn't 2msec. Imposimple, right? Is there spikes? Why is this happening? Wrong technik or it is difficult to make the work of the USART with code? I'm sure that the code is right but i have not yet an oscilloscope or logic probe to see what really happens. Sorry if i tired you but i want to explain some details that are important to understand the problem. Any opinion is acceptable.
Thanks.
Thanks.
