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First Draft proposal Protocol

PostPosted: Mon Sep 24, 2007 2:42 am
by Thonord
Dokument is not nicely formated. Was written in Word, but I find no way to attach a file to a post.

Draft Proposal

Serial Protocol for eSlave

1. This protocol is intended for use between eSlave units for control of flash
units from different vendors. The eSlave units are identical and their
function (Master/Slave)is determined by a Signature setting.

The protocol contains a minimum of instructions and is dependent upon simple
vendor spesific drivers to perform instruction conversion.

A Collision avoidance (CA) scheme is implemented to allow bi-directional
communications between individual slaves and the Master in Group Mode (GM).
CA is Time-slot based.
Individual slaves cannot communicate.

The protocol contains a simple Positive Ack Automatic Request for Repeat
(ARQ) engine.

2. Protocol Basics

The eSlave unit set as Master exchanges data packets of variable byte length
with individual eSlave slaves in either GM or Point to Point (PP) mode.
Serial line paramaters used are: 8 bit, no parity. No flow control is used.
All arithmetic data is transmitted least significant byte first ("little

3. Protocol Size

3.1. Type of session

3.1.1. GM 2 bytes
Header, CheckSum

3.1.2. PP 3 or 4 Bytes
Header, CheckSum
Header, Control Packet, Sub Control Packet, ChkSum

4. Elementary units

4.1. Header. Single Byte (Information at Bit level

4.1.1. Bit 8. Identifies GM or PP operation
O = GM.
1 = PP

4.1.2. GM mode
Bit 7.
O = Passive
1 = Trigger

Bit 6.
O = Passive
1 = Quench

Bit 5. Power saving mode and forces Initial unit sign-in after
setup. Unit sign-in takes place in PP
O = Passive
1 = Resume/Sign In

Bit 4.
O = Passive
1 = Off

Bit 3.
O = Passive
1 = St-By

Bit 2.
O = Passive
1 = Master sync

Bit 1.
Future expansion, leave at 0

4.1.3. PP Mode

Bit 7. Used in conjunction with the Control Packet
O = Set
1 = Get

Bit 6.
O = Passive
1 = Warning/Sign-in

Bit 5.
O = Passive
1 = NAK

Bit 4.
O = Passive
1 = Ack

Bit 3-2-1
Signature/Unit ID. Decimal 0-7
0 = Master, n = Slave n If bits 6&5&4 = 0 then
PP = 2 Bytes (Header + ChkSum)
PP = 4 Bytes (Header + Control Packet + Sub Control Packet +

4.2. Control Packet
(Set/Get from Header Bit 7)
The packet has the following structure:

4.2.1. Flash Mode and Signature. (information derived at Byte level

&H0n Flash Operation Mode
&H1n Flash Power Mode
&H2n Flash TTL/E-TTL Mode
&H3n Flash Zoom Mode

&Hn0-7 Signature

Example &H14. Slave 4, Flash power Mode

4.3. Sub Control Packet
The packet has the following structure:

4.3.1. Set/Get from Header Bit 7 and Control Code Packet
Control. (Single ByteInformation at Byte level

4.3.2. Flash Operation Mode
&H00 (TTL/E-TTL)
&H01 (AUTO)
&H02 (OFF)
&H03 (FILL-IN)
&H04 (AUTO Red-eye)
&H05 (Slow)
&H06 (Slow-Sync)
&H07 (Slow-Red-eye)
&H08 (FILL-IN Red-eye)
&H09 (FILL-IN Sync)
&H0A(Manual power)

4.3.3. Manual Power Mode
&H11 (1/4 power
&H12 (1/8 power
&H13 (1/16power
&H14 (1/32power
&H15 (1/64power)

4.3.4. Flash TTL/E-TTL Mode
&H20 \
&H21 |
&H22 |
&H23 |
&H24 |
&H25 \
&H26 / I have No idea
&H27 |
&H28 |
&H29 |
&H2A /

4.3.5. Zoom Mode
&H31 10 mm
&H32 20 mm
&H33 30 mm
&H34 40 mm
&H35 50 mm
&H36 60 mm
&H37 70 mm
&H38 80 mm

5. Collision Avoidance

CA is accomplished by each slave delaying their responce to a Master GM
transmission by a set number of msec, multiplied with their Signature.
Synchronism is maintained by the use of a Master Sync
Master Sync is transmitter at x min intervals

6. ARQ
Ack or Nak are determined upon the ChkSum
There are three scenarios

* Received Ack – All well
* Received Nak – PP mode repeated. GM mode repeated in PP
* No reception – Nak asumed

7. Unique situations

7.1. Trigger
When a trigger signal is sent and a Nak or no responce is received
from a slave, the trigger signal is not repeated. In this case an
Audio? and LED Trigger Failure indication is given by the Master.

7.2. Master sync
When a Master Sync signal is sent and a Nak or no responce is
received from a slave, The Master Sync is repeated in GM until Ack
is received from all slaves in responce to the same Master Sync

PostPosted: Mon Sep 24, 2007 9:01 am
by seaton
Well done Thonord on a great proposal, I've not gone though it in detail, but I think it's a great start.


PostPosted: Fri Dec 21, 2007 4:06 am
by seaton
I've put this up on the wiki