# Is port D on BL1800 JackRabbit Single-Board Computer different from other ports (A,B,C)? **URL:** \ **Category:** Rabbit\ **Created:** [January 19, 2012, 4:09pm UTC](https://forums.digi.com/t/is-port-d-on-bl1800-jackrabbit-single-board-computer-different-from-other-ports-a-b-c/9768 "2012-01-19T16:09:13Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![homersimpson](https://avatars.discourse-cdn.com/v4/letter/h/cab0a1/32.png) [@homersimpson](https://forums.digi.com/u/homersimpson)\ **Post date:** [January 19, 2012, 4:09pm UTC](https://forums.digi.com/t/is-port-d-on-bl1800-jackrabbit-single-board-computer-different-from-other-ports-a-b-c/9768/1 "2012-01-19T16:09:13Z")
I am having terrible time trying to figure out how to read and write to Port D on BL1800 JackRabbit Single-Board Computer right from within the Processor. I have searched through documentations and found very few useful information but the following: ```auto This library contains 3 RS485 serial interface functions for the JackRabbit board. These functions are to be used with the serial port D library functions in rs232.lib because serDopen utilizes PC0 (TXD) and PC1 (RXD), which are connected to pin 4 and pin 1 of the RS485 chip. This chip is half duplex requiring pin 3 (Data Enable) to be high for pins 6 and 7 to act as output and low for those pins to act as input. ------------------------- | | | DI 4|------- (PC0 on JackRabbit) (485+ on JackRabbit) -------|6 DO/RI RO 1|------- (PC1 on JackRabbit) | | | ____ | (485- on JackRabbit) -------|7 DO/RI | | DE 3|------- (PD5 on JackRabbit) | RE 2|O-----------| ------------------------- | SP483EN | \/ void Jr485Init(); Setup parallel port D pins for 485 use void Jr485Tx(); Sets (high) pin 3 (DE) of the RS485 chip to disable Rx, enable Tx void Jr485Rx(); Resets (low) pin 3 (DE) of the RS485 chip to disable Tx, enable Rx ``` Apparently, I can write and read to Port D from a PC, but I can only write to Port D from within the processor and not able to read. Am I missing a key information about Port D? This is how I write on Port D from Dynamic C program: Jr485Tx(); waitfordone { cof\_serDwrite(&dxout[0],5) }; while(BitRdPortI(SDSR,SS\_TFULL\_BIT) != 0); while(BitRdPortI(SDSR,SS\_TPRG\_BIT) == 1); This is how I read on Port D from Dynamic C program: Jr485Rx(); waitfordone { dxin[0] = cof\_serDgetc() }; if(dxin[0] == 0xff) // if-1 { waitfordone { myret = cof\_serDread(&dxin[1],5,20) }; Again, these codes can communicate flawlessly with a PC through port D but not when the Jackrabbit itself is trying to read the incoming bytes from an external device. Is Port D meant for RS232 communication only? Any help or hints will be greatly appreciated. ---
**Author:** ![MargaretK](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@MargaretK](https://forums.digi.com/u/MargaretK)\ **Post date:** [May 10, 2013, 6:46pm UTC](https://forums.digi.com/t/is-port-d-on-bl1800-jackrabbit-single-board-computer-different-from-other-ports-a-b-c/9768/2 "2013-05-10T18:46:18Z")
The schematic shows that RS232 signals are only on Ports B and C, not on port D ---
**Author:** ![homersimpson](https://avatars.discourse-cdn.com/v4/letter/h/cab0a1/32.png) [@homersimpson](https://forums.digi.com/u/homersimpson)\ **Post date:** [July 15, 2014, 3:29pm UTC](https://forums.digi.com/t/is-port-d-on-bl1800-jackrabbit-single-board-computer-different-from-other-ports-a-b-c/9768/3 "2014-07-15T15:29:47Z")
Is that mean Port D can only do RS485 signals? ---
**Author:** ![MargaretK](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@MargaretK](https://forums.digi.com/u/MargaretK)\ **Post date:** [July 15, 2014, 3:35pm UTC](https://forums.digi.com/t/is-port-d-on-bl1800-jackrabbit-single-board-computer-different-from-other-ports-a-b-c/9768/4 "2014-07-15T15:35:03Z")
The Jackrabbit has one RS-485 serial channel, which is connected to the Rabbit 2000 serial port D through U6, an RS-485 transceiver. Documentation and schematics can be found at the following link: [http://www.digi.com/support/productdetail?pid=4513&type=documentation](http://www.digi.com/support/productdetail?pid=4513&type=documentation) ---
**Author:** ![MargaretK](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@MargaretK](https://forums.digi.com/u/MargaretK)\ **Post date:** [July 15, 2014, 3:50pm UTC](https://forums.digi.com/t/is-port-d-on-bl1800-jackrabbit-single-board-computer-different-from-other-ports-a-b-c/9768/5 "2014-07-15T15:50:51Z")
Please try the following sample for the Jackrabbit: #define DINBUFSIZE 15 #define DOUTBUFSIZE 15 void main( void ){ int nEcho,nReply; char cChar; Jr485Init ();// Init RS485 Control (PD5) serDopen ( 9600 );// Open Serial Port D for (;šŸ˜‰ {// Forever for (cChar=ā€˜aā€™;cChar\<=ā€˜zā€™;++cChar){ // Send Alphabet Jr485Tx ();// Enable RS485 Transmitter serDputc ( cChar );// Send Byte while ((nEcho = serDgetc ()) == -1); // Wait for Echo Jr485Rx ();// Disable RS485 Transmitter while ((nReply = serDgetc ()) == -1); // Wait for Reply printf ( "%02x -\> %02x ",nEcho,nReply ); } } } If the characters are not coming out correctly then you may not have the baud rate correct. ---
**Author:** ![MargaretK](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@MargaretK](https://forums.digi.com/u/MargaretK)\ **Post date:** [July 15, 2014, 3:52pm UTC](https://forums.digi.com/t/is-port-d-on-bl1800-jackrabbit-single-board-computer-different-from-other-ports-a-b-c/9768/6 "2014-07-15T15:52:53Z")
```auto [ #define DINBUFSIZE 15 #define DOUTBUFSIZE 15 void main( void ){ int nEcho,nReply; char cChar; Jr485Init ();// Init RS485 Control (PD5) serDopen ( 9600 );// Open Serial Port D for (;;) {// Forever for (cChar='a';cChar<='z';++cChar){ // Send Alphabet Jr485Tx ();// Enable RS485 Transmitter serDputc ( cChar );// Send Byte while ((nEcho = serDgetc ()) == -1); // Wait for Echo Jr485Rx ();// Disable RS485 Transmitter while ((nReply = serDgetc ()) == -1); // Wait for Reply printf ( "%02x -> %02x ",nEcho,nReply ); } } } ] I hope the copied text comes out better with this try ``` ---
**Author:** ![MargaretK](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@MargaretK](https://forums.digi.com/u/MargaretK)\ **Post date:** [July 15, 2014, 3:54pm UTC](https://forums.digi.com/t/is-port-d-on-bl1800-jackrabbit-single-board-computer-different-from-other-ports-a-b-c/9768/7 "2014-07-15T15:54:27Z")
the following line is not copying correctly: for (;; It should be for ( with two ; ---
**Author:** ![homersimpson](https://avatars.discourse-cdn.com/v4/letter/h/cab0a1/32.png) [@homersimpson](https://forums.digi.com/u/homersimpson)\ **Post date:** [July 16, 2014, 9:46am UTC](https://forums.digi.com/t/is-port-d-on-bl1800-jackrabbit-single-board-computer-different-from-other-ports-a-b-c/9768/8 "2014-07-16T09:46:08Z")
Thank you soooooooooooooo much. Now, I am able to read the in coming bytes correctly. šŸ™‚ XOXOXOXOXOXOXO @}}ā€“}}------