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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. |
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| | | == 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>
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| # stty -F /dev/ttySP0 raw
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| # stty -F /dev/ttySP0 -echo -echoe -echok
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| # stty -F /dev/ttySP0 rs485
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| </pre>
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| | |
| * Set extra delays for TXEN/RTS signaling before and after the transmitted packet (in microseconds):
| |
| <pre class=apf>
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| # stty -F /dev/ttySP0 rs485delaybefore 100
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| # stty -F /dev/ttySP0 rs485delayafter 100
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| </pre>
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| | |
| * To get current RS485 parameters. (If the port device supports the RS485 options you will see the last two lines)
| |
| <pre class=apf>
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| # stty -F /dev/ttySP0
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| speed 9600 baud; line = 0;
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| intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>;
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| eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R;
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| werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0;
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| -brkint -imaxbel
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| rs485 -rs485rtsonsend -rs485rtsaftersend -rs485rxduringtx
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| rs485delaybefore = 100; rs485delayafter = 100; rs485delaylastchartx = 1250;
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| </pre>
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| Please note:
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| * You can't set the "rs485delaylastchartx" parameter, it's calculated automatically from the baudrate.
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| Special notes for the APF28/iMX28 mxs-auart driver:
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| * All delays are in microseconds.
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| * The "rs485delaylastchartx" parameter is not used in DMA mode.
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| * The parameters: "rs485rtsonsend" "rs485rtsaftersend" "rs485rxduringtx" are not used.
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| * 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.
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| | |
| === C code ===
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| * The RS485 mode can be turned on with ioctl calls from C code, here is the example:
| |
| <source lang="C">
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| #include <stdio.h>
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| #include <fcntl.h>
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| #include <linux/ioctl.h>
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| #include <linux/serial.h>
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| #include <asm-generic/ioctls.h> /* TIOCGRS485 + TIOCSRS485 ioctl definitions */
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| | |
| int main(void) {
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| struct serial_rs485 rs485conf;
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| | |
| int fd = open ("/dev/ttySP0", O_RDWR);
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| if (fd < 0) {
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| printf("Error: Can't open: /dev/ttySP0\n");
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| }
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| | |
| | |
| /* Don't forget to read first the current state of the RS485 options with ioctl.
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| If You don't do this, You will destroy the rs485conf.delay_rts_last_char_tx
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| parameter which is automatically calculated by the driver when You opens the
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| port device. */
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| if (ioctl (fd, TIOCGRS485, &rs485conf) < 0) {
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| printf("Error: TIOCGRS485 ioctl not supported.\n");
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| }
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| | |
| /* Enable RS485 mode: */
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| rs485conf.flags |= SER_RS485_ENABLED;
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| | |
| /* Set rts/txen delay before send, if needed: (in microseconds) */
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| rs485conf.delay_rts_before_send = 0;
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| | |
| /* Set rts/txen delay after send, if needed: (in microseconds) */
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| rs485conf.delay_rts_after_send = 0;
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| if (ioctl (fd, TIOCSRS485, &rs485conf) < 0) {
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| printf("Error: TIOCSRS485 ioctl not supported.\n");
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| }
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| | |
| fcntl(fd, F_SETFL, 0);
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| int n = write(fd, "ABC\r\n", 5);
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| if (n < 0) {
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| /* Error handling */
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| }
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| | |
| if (close (fd) < 0) {
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| printf("Error: Can't close: /dev/ttySP0\n");
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| }
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| }
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| </source>
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| | |
| === Hardware Notes ===
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| * The RS485 Transmit Enable (TXEN) output will be the RTS pin of the uart.
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| * The TXEN/RTS output is _active low_, it must be inverted to use it with the popular RS485 transceiver ICs.
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| * 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.
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