Differences

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--- rc:dev:sbus_client [2014/10/08 23:06] – [Trame] redox
+++ rc:dev:sbus_client [2023/11/24 21:55] (current) – external edit 127.0.0.1
@@ Line 2: / Line 2: @@
 ## Overview
+Well... Not much to say here. I have the radio, the receiver, a Teensy3.1 and some spare time. Let's hook everything together =D
 ## Protocol
@@ Line 7: / Line 10: @@
 ### Technical details
-    Baudrate...
+The technical details originaly come from __Uwe Gartmann__ from the MBed website (source link in the Links section). Because it would have been to easy to use standard settings, SBus serial communications use:
-### Trame
+* A baudrate of 100000 b/s
+* An inverted logic
+* One parity bit
+* Two stop bits
+* MSB first (that the only common thing !)
+Luckily, the Teensy3 can manage that =)
+The SBus protocol sends a message every 7ms (high speed mode) or every 14ms (low speed mode).
+### SBus protocol
+A common SBus message requires 25 bytes of data:
     F0 xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx yy 00
-* (0x)F0 is the start byte. It should always be 0xF0. You can sync on that I guess if you want to.
+* F0 is the start byte. It should always be 0xF0. You can sync on that I guess if you want to.
-* (0x)xx are the data bytes. There should be 22 of them: SBus manages 16 analog channels, and uses 11bits for each, so 11*16/8 => 22 bytes.
+* xx are the data bytes. There should be 22 of them. SBus manages 16 analog channels, and uses 11bits for each, so 11*16/8 => 22 bytes.
-They could have made our lives easier and used 12bits per channel, but No... So:
+  * CH1 uses the first data byte (let's call it D0), and the 3 Most Significant Bits (MSB) of D1
-  * CH1 uses the 8 msb of byte  0, the 3 msb of byte 1.
+  * CH2 uses the 5 Least Significant Bits (LSB) of D1, and the 6 MSB of D2
-  * CH2 uses the 5 lsb of byte  2, the 6 msb of byte 3.
+  * And so on... CH3 uses the 2 LSB  of D2, the whole D3, and the MSB of D4...See, its not that easy to process (12bits would have been too simple ^^ )...
-  * And so on. See, its not that easy to process...
-* (0x)yy is the flag byte
+* yy is the flag byte
   * Bit 7 (0x80) is CH17, it's a digital/binary channel.
   * Bit 6 (0x40) is CH18, same.
@@ Line 27: / Line 41: @@
   * Bit 4 (0x10) indicates __Failsafe mode__
   * Bits 3-0 are not used and sould be 0
-* (0x)00 is the stop byte. It should always be 0x00. You can also do some check to check there was no lost/added byte in the serial communication.
+* 00 is the stop byte. It should always be 0x00. You can also do some check to check there was no lost/added byte in the serial communication.
 ### Typical Frame
-    F0 2E 90 FB 1F 1D EC 8E 0F B6 F3 DE 07 C6 A0 D4 1A 83 50 6A 0D 41 A8 20 00
+    F0 2E 90 FB 1F 1D EC 8E 0F B6 F3 DE 07 C6 A0 D4 1A 83 50 6A 0D 41 A8 00 00
+* Starts with 0xF0
+* Flag is 0x00, no error.
+* Ends with 0x00
 ### Radio off
@@ Line 42: / Line 61: @@
 ## Code
+Well, it's heavily adapted from the [[:rc:dev:sport_master|SmartPort Master code]]. Same warnings, same wiring (Gnd on Gnd, Vcc on Vcc, SBus signal on TX1/PB17). It doesn't do much, but might help start/debug another project...
+Here's the last version of the code: {{:rc:dev:sbus:tsysbusrecv_20141008_1942.tar.gz|}}
+## Next ?
+* Decode the CH* values
+* Port to Attiny (cost, embeddable, ...)
+* Emulates a joystick with Teensy3, so I can use the RC simulator softwares without any cable.
 ## Links