JohnJohn20
Advanced Member level 4
Hi. I would like to use a PIC to control a GSM mobile phone to send an SMS via the F Bus connection. I am OK with the PIC control but not so with setting up the serial data transfer between the PIC and the phone.
The article Nokia F-Bus Protocol (at **broken link removed**) gives some good information but as a beginner I need to check my understanding. Please let me know if I have this straight.
There are 4 connections on the back of the phone: MBUS, RX, TX and GND. F-Bus protocol uses the TX and RX pins as a full-duplex bus at 115,200bps, 8 data bits, no parity, one stop bit.
1. Can I use a PIC (via opto couplers) to:
- Switch the RX pin to +3.3V and ground to transmit to the phone? and
- Detect the incoming pulses at the TX pin to receive data from the phone?
2. Is the process for sending data to the phone as follows:
- While the RX pin is held high no data is transmitted.
- Then make the RX pin low for 1 period (1/115,200 seconds) to signal to the phone that data is coming.
- Then make the RX pin high or low for 8 periods (according to the 8 bit word I want to transmit to the phone).
- And then make the RX pin go high for 1 period (or longer) to signal end of transmission.
3. The article also says the first thing to do is "synchronize the UART in the phone with your PIC" by sending a string of 0x55 or 'U' 128 times.
To do this do I send binary '01010101' 128 times as described above?
4. Does this "synchronization" synchronize the phone with PIC transmission frequency or does the transmission frequency need to be very close to 115.200 kHz? I would like to use a lower frequency of about 32 kHz.
Thank you for your time.
The article Nokia F-Bus Protocol (at **broken link removed**) gives some good information but as a beginner I need to check my understanding. Please let me know if I have this straight.
There are 4 connections on the back of the phone: MBUS, RX, TX and GND. F-Bus protocol uses the TX and RX pins as a full-duplex bus at 115,200bps, 8 data bits, no parity, one stop bit.
1. Can I use a PIC (via opto couplers) to:
- Switch the RX pin to +3.3V and ground to transmit to the phone? and
- Detect the incoming pulses at the TX pin to receive data from the phone?
2. Is the process for sending data to the phone as follows:
- While the RX pin is held high no data is transmitted.
- Then make the RX pin low for 1 period (1/115,200 seconds) to signal to the phone that data is coming.
- Then make the RX pin high or low for 8 periods (according to the 8 bit word I want to transmit to the phone).
- And then make the RX pin go high for 1 period (or longer) to signal end of transmission.
3. The article also says the first thing to do is "synchronize the UART in the phone with your PIC" by sending a string of 0x55 or 'U' 128 times.
To do this do I send binary '01010101' 128 times as described above?
4. Does this "synchronization" synchronize the phone with PIC transmission frequency or does the transmission frequency need to be very close to 115.200 kHz? I would like to use a lower frequency of about 32 kHz.
Thank you for your time.