dali/bacnet_stack
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Changed Tturnaround time in MS/TP modules to be a minimum of 2ms, or use a dummy transmit of 4 bytes while the transceiver is disabled. 1ms delay will always give smaller than 1ms of delay due to silence timer tick.

Browse Source
This commit is contained in:
skarg
2010-10-18 20:42:26 +00:00
parent a5f24fa19f
commit 57781b40cb
8 changed files with 72 additions and 55 deletions
Download Patch File Download Diff File Expand all files Collapse all files
bacnet-stack/ports/atmega168/rs485.c
+29 -33
View File
@@ -44,18 +44,6 @@ static uint8_t LED3_Off_Timer;
/* baud rate */
static uint32_t RS485_Baud = 9600;
/* The minimum time after the end of the stop bit of the final octet of a */
/* received frame before a node may enable its EIA-485 driver: 40 bit times. */
/* At 9600 baud, 40 bit times would be about 4.166 milliseconds */
/* At 19200 baud, 40 bit times would be about 2.083 milliseconds */
/* At 38400 baud, 40 bit times would be about 1.041 milliseconds */
/* At 57600 baud, 40 bit times would be about 0.694 milliseconds */
/* At 76800 baud, 40 bit times would be about 0.520 milliseconds */
/* At 115200 baud, 40 bit times would be about 0.347 milliseconds */
/* 40 bits is 4 octets including a start and stop bit with each octet */
#define Tturnaround (40UL)
/* turnaround_time_milliseconds = (Tturnaround*1000UL)/RS485_Baud; */
/****************************************************************************
* DESCRIPTION: Initializes the RS485 hardware and variables, and starts in
* receive mode.
@@ -137,26 +125,6 @@ bool RS485_Set_Baud_Rate(
return valid;
}
/****************************************************************************
* DESCRIPTION: Waits on the SilenceTimer for 40 bits.
* RETURN: none
* ALGORITHM: none
* NOTES: none
*****************************************************************************/
void RS485_Turnaround_Delay(
void)
{
uint16_t turnaround_time;
/* delay after reception before trasmitting - per MS/TP spec */
/* wait a minimum 40 bit times since reception */
/* at least 1 ms for errors: rounding, clock tick */
turnaround_time = 1 + ((Tturnaround * 1000UL) / RS485_Baud);
while (Timer_Silence() < turnaround_time) {
/* do nothing - wait for timer to increment */
};
}
/****************************************************************************
* DESCRIPTION: Enable or disable the transmitter
* RETURN: none
@@ -173,6 +141,35 @@ void RS485_Transmitter_Enable(
}
}
/****************************************************************************
* DESCRIPTION: Waits on the SilenceTimer for 40 bits.
* RETURN: none
* ALGORITHM: none
* NOTES: none
*****************************************************************************/
void RS485_Turnaround_Delay(
void)
{
uint8_t nbytes = 4;
RS485_Transmitter_Enable(false);
while (nbytes) {
while (!BIT_CHECK(UCSR0A, UDRE0)) {
/* do nothing - wait until Tx buffer is empty */
}
/* Send the data byte */
UDR0 = 0xff;
nbytes--;
}
/* was the frame sent? */
while (!BIT_CHECK(UCSR0A, TXC0)) {
/* do nothing - wait until the entire frame in the
Transmit Shift Register has been shifted out */
}
/* Clear the Transmit Complete flag by writing a one to it. */
BIT_SET(UCSR0A, TXC0);
}
/****************************************************************************
* DESCRIPTION: Timers for delaying the LED indicators going off
* RETURN: none
@@ -253,7 +250,6 @@ void RS485_Send_Data(
Timer_Silence_Reset();
}
/****************************************************************************
* DESCRIPTION: Return true if a framing or overrun error is present
* RETURN: true if error