I'm developing a project for a Master Modbus using MSP430F149. I'm using in this project a external crystal of 32K.
The parameter i'm using are, as follow: /* Baud Rate table: clock: 8000000Hz desired baud rate: first element UBR00: second element UBR10: third element UMCTL0: fourth element http://mspgcc.sourceforge.net/baudrate.html - Thanks to Pedro Zorzenon Neto -- pzn at debian.org */ const struct sserial serial[] = { { 1200, 0x0A, 0x1A, 0x5B }, { 2400, 0x05, 0x0D, 0x52 }, { 4800, 0x82, 0x06, 0x5B }, { 9600, 0x41, 0x03, 0x09 }, { 19200, 0xA0, 0x01, 0x5B }, { 28800, 0x15, 0x01, 0xBB }, { 38400, 0xD0, 0x00, 0x11 }, { 57600, 0x8A, 0x00, 0xEF }, { 115200, 0x45, 0x00, 0xAA }, { 0, 0, 0, 0 } } ; My project is working for 115200 and 57600 kbps, with parity bit, stop bit and number of byte changes. The same uart, uart 0, is used for debug, in the terminal with a default and unchangeble value 57600,8N1 and is also used for modbus communication (RS232 or RS485 - external jumper selected). Modbus is ok for 57600 and 115200 with many equipments. I also tested for debug in the computer terminal, using RS232 alternative, printing some sentences and it worked for all baud rates: 1200, 2400, 4800, 9600, 19200, 28800, 38400, 57600, 115200. So, it's not a problem of registers value. When I want to communicate in Modbus, I switch a MUX and change RS232 to (RS485 or RS232 - choose by external jumper) communication and get the values for desired baud rate in the table, and the value for parity bit, stop bit and number of bits in ctl_u0 (unsigned char, entered by user). P2OUT |= CLP_M; UBR00 = brate0; UBR10 = brate1; UMCTL0 = ctl_um0; U0CTL = ctl_u0; When the modbus communication is over, I load the default settings(57600,8N1): P2OUT &= ~CLP_M; UBR00=0x8A; UBR10=0x00; UMCTL0=0xEF; U0CTL = CHAR + SPB; U0TCTL = SSEL1; Why does this project only works for 57600 and 115200? I have not this answer. If anyone, please could help me solve this problem. Thiago P. F. S. Lima Eletronic Engineer
