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| | + | == About Me == |
| | I am IP Network and Datacenter engineer, currently I'm working for an Internet Service Provider in Hungary. | | I am IP Network and Datacenter engineer, currently I'm working for an Internet Service Provider in Hungary. |
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| | * Data logger for Saia Sbus based intelligent power meters. | | * Data logger for Saia Sbus based intelligent power meters. |
| | | | |
| − | | + | == My works comitted to ArmadeuS project == |
| − | == RS485 == | + | * [[RS-485]] for APF28/iMX28 mxs-auart and busybox stty patch |
| − | Informations and mini HOWTOs for my APF28/iMX28 mxs-auart and busybox stty patches.
| + | * [[OneWire GPIO bus Master]] for APF28DEV |
| − | | + | |
| − | === Linux stty ===
| + | |
| − | * Setup APF28 serial port for RS485 communication: | + | |
| − | <pre class=apf>
| + | |
| − | # stty -F /dev/ttySP0 raw
| + | |
| − | # stty -F /dev/ttySP0 -echo -echoe -echok
| + | |
| − | # stty -F /dev/ttySP0 rs485
| + | |
| − | </pre>
| + | |
| − | | + | |
| − | * Set extra delays for TXEN/RTS signaling before and after the transmitted packet (in microseconds):
| + | |
| − | <pre class=apf>
| + | |
| − | # stty -F /dev/ttySP0 rs485delaybefore 100
| + | |
| − | # stty -F /dev/ttySP0 rs485delayafter 100
| + | |
| − | </pre>
| + | |
| − | | + | |
| − | * To get current RS485 parameters. (If the port device supports the RS485 options you will see the last two lines)
| + | |
| − | <pre class=apf>
| + | |
| − | # stty -F /dev/ttySP0
| + | |
| − | speed 9600 baud; line = 0;
| + | |
| − | intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>;
| + | |
| − | eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R;
| + | |
| − | werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0;
| + | |
| − | -brkint -imaxbel
| + | |
| − | rs485 -rs485rtsonsend -rs485rtsaftersend -rs485rxduringtx
| + | |
| − | rs485delaybefore = 100; rs485delayafter = 100; rs485delaylastchartx = 1250;
| + | |
| − | </pre>
| + | |
| − | Please note:
| + | |
| − | * You can't set the "rs485delaylastchartx" parameter, it's calculated automatically from the baudrate.
| + | |
| − | Special notes for the APF28/iMX28 mxs-auart driver:
| + | |
| − | * All delays are in microseconds.
| + | |
| − | * The "rs485delaylastchartx" parameter is not used in DMA mode.
| + | |
| − | * The parameters: "rs485rtsonsend" "rs485rtsaftersend" "rs485rxduringtx" are not used.
| + | |
| − | * If the RS485 mode is turned on, it will override (turn off) the RTS/CTS hardware flow settings of the uart, don't care what is configured.
| + | |
| − | | + | |
| − | === C code ===
| + | |
| − | * The RS485 mode can be turned on with ioctl calls from C code, here is the example:
| + | |
| − | <source lang="C">
| + | |
| − | #include <stdio.h>
| + | |
| − | #include <fcntl.h>
| + | |
| − | #include <linux/ioctl.h>
| + | |
| − | #include <linux/serial.h>
| + | |
| − | #include <asm-generic/ioctls.h> /* TIOCGRS485 + TIOCSRS485 ioctl definitions */
| + | |
| − | | + | |
| − | int main(void) {
| + | |
| − | struct serial_rs485 rs485conf;
| + | |
| − | | + | |
| − | int fd = open ("/dev/ttySP0", O_RDWR);
| + | |
| − | if (fd < 0) {
| + | |
| − | printf("Error: Can't open: /dev/ttySP0\n");
| + | |
| − | }
| + | |
| − | | + | |
| − | | + | |
| − | /* Don't forget to read first the current state of the RS485 options with ioctl.
| + | |
| − | If You don't do this, You will destroy the rs485conf.delay_rts_last_char_tx
| + | |
| − | parameter which is automatically calculated by the driver when You opens the
| + | |
| − | port device. */
| + | |
| − | if (ioctl (fd, TIOCGRS485, &rs485conf) < 0) {
| + | |
| − | printf("Error: TIOCGRS485 ioctl not supported.\n");
| + | |
| − | }
| + | |
| − | | + | |
| − | /* Enable RS485 mode: */
| + | |
| − | rs485conf.flags |= SER_RS485_ENABLED;
| + | |
| − | | + | |
| − | /* Set rts/txen delay before send, if needed: (in microseconds) */
| + | |
| − | rs485conf.delay_rts_before_send = 0;
| + | |
| − | | + | |
| − | /* Set rts/txen delay after send, if needed: (in microseconds) */
| + | |
| − | rs485conf.delay_rts_after_send = 0;
| + | |
| − | | + | |
| − | if (ioctl (fd, TIOCSRS485, &rs485conf) < 0) {
| + | |
| − | printf("Error: TIOCSRS485 ioctl not supported.\n");
| + | |
| − | }
| + | |
| − | | + | |
| − | fcntl(fd, F_SETFL, 0);
| + | |
| − | int n = write(fd, "ABC\r\n", 5);
| + | |
| − | if (n < 0) {
| + | |
| − | /* Error handling */
| + | |
| − | }
| + | |
| − | | + | |
| − | if (close (fd) < 0) {
| + | |
| − | printf("Error: Can't close: /dev/ttySP0\n");
| + | |
| − | }
| + | |
| − | }
| + | |
| − | </source>
| + | |
| − | | + | |
| − | === Hardware Notes ===
| + | |
| − | * The RS485 Transmit Enable (TXEN) output will be the RTS pin of the uart.
| + | |
| − | * The TXEN/RTS output is _active low_, it must be inverted to use it with the popular RS485 transceiver ICs.
| + | |
| − | * When the u-boot runs and the board start to boot, the RTS pin works as input, please add a pullup resistor to this pin before the inverter, to prevent RS485 bus lockups.
| + | |
I am IP Network and Datacenter engineer, currently I'm working for an Internet Service Provider in Hungary.
My hobby is programming embedded systems and creating my own small electronic boards.
