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OA47

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Posted: 08:32pm 16 May 2017

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Could anyone think of a way that I might be able to send and receive 1200,7,e,1,N from a Micromite ? Could I receive at 1200,8 read in the data and drop the 8th bit?
Graeme

MicroBlocks

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Posted: 09:05pm 16 May 2017

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If i read it right, a 1200 baud rate with 7 databits,1 even parity bit and one stop bit has in total 9 bits.
If you setup 1200 baud , 8 bits, no parity and one stop bit would also be 9 bits.
Receiving is easy as what you already thought. Just drop the 8th bit.
Easiest to do an AND with 127 (&B01111111)

Sending would require you to take the 7 bit data and use the 8th bit as a parity.
For even parity you would need to count the 1's and if the count is uneven then set the parity bit. The count AND 1 will give you a 0 or 1 for even or uneven.

Edited by MicroBlocks 2017-05-18

Microblocks. Build with logic.

OA47

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Posted: 10:14pm 21 Jun 2017

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Not having much luck here so I thought I would post my try and see if someone could see the error in my method. Just dealing with the transmit side first, as per the limited documentation I have, the query to acknowledge active for the device attached to the micromite is "a!" at 1200,7,e,1 which I have worked this way:

"a"= ASC 97 =1100001 and adding parity bit= 11000010 which= chr$(194) at 8 bits no parity
"I"= ASC 73 =1001001 and adding parity bit= 10010010 which= chr$(146) at 8 bits no parity
So I am sending the query string as chr$(194)+chr$(146)

QUERY$=Chr$(194)+Chr$(66) 'ACKNOWLEDGE ACTIVE a!

Pin(7)=1
Open "COM2:1200" As #1
Print Time$; " THE QUERY STRING IS ";QUERY$
Print #1, QUERY$
Pause 100
Pin(7)=0
REPLY$=Input$(10,#1)
Close #1

Print Time$;" THE REPLY STRING IS ";REPLY$

Looping the Com2 pins I can see my data back but I cant get a response from the device.
Graeme

matherp
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Posted: 11:04pm 21 Jun 2017

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I think you have put the parity bit at the wrong end - it should be the MSB

JohnS
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Posted: 11:17pm 21 Jun 2017

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Also, you probably want a semi-colon (;) at the end of each PRINT #1

(unless you want CR / LF sent as well as your chars)

John

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Posted: 12:00am 22 Jun 2017

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"a" = CHR$(97) = 0110 0001 has three ones, use OR 128 (1000 0000) = 1110 0001 (225)
"!" = CHR$(73) = 0100 1001 has three ones, use OR 128 (1000 0000) = 1100 1001 (201)

Query$ = CHR$(225) + CHR$(201)

Not able to test it, but i think those values are right.

Microblocks. Build with logic.

OA47

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Posted: 12:13am 22 Jun 2017

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Quote I think you have put the parity bit at the wrong end - it should be the MSB

Does this mean that a character such as "!" which is ascii 33 &B100001 having even number of ones would still be the same value as the msb will be a zero?

matherp
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Posted: 12:27am 22 Jun 2017

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Quote Does this mean that a character such as "!" which is ascii 33 &B100001 having even number of ones would still be the same value as the msb will be a zero?

Yes

OA47

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Posted: 12:38pm 22 Jun 2017

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Thank you for your direction and assistance. Still no response from the device. I might drag out one of my old pc's with a serial port and see if I can pump some life back into it. Will see if I get any response at 1200,7,e with it.
Graeme

TassyJim

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Posted: 01:23pm 22 Jun 2017

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Try this

Quote
a$="hello there!"

FOR n = 1 TO LEN(a$)
ch$=MID$(a$,n,1)
che$=even$(ch$)

PRINT ch$," ",BIN$(ASC(che$),8)," ",ASC(che$)

NEXT n

FUNCTION even$(c$)
' given a character, returns a character with even parity set in 8th bit
LOCAL n, par, a
a = ASC(c$)
FOR n = 1 TO 7
a = a*2
par = (a AND &B10000000) XOR par
NEXT n
even$ = CHR$((ASC(c$) AND &B01111111) OR par)
END FUNCTION

It's not the most efficient way of adding parity but hopefully it is clear enough to follow.

Receiving characters is the easy part. Simply mask off the 8th bit.
ch$= chr$(asc(ch$) AND &B01111111))

Jim

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TassyJim

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Posted: 02:48pm 22 Jun 2017

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You will also need to include the cr lf pair in the parity code.

Quote a$="hello there!"+CHR$(13)+CHR$(10)

cr with even parity is chr$(141)
lf stays the same.

Jim

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OA47

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Posted: 06:05pm 22 Jun 2017

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Thanks Jim for your code but I think I have a more serious issue with the serial transfer. I am not sure if the response is inverted or modified in some way. I have connected the device to a serial port @1200,7,E,1 with Putty but still don't read a response. I have measured the current draw of the device and it sits at 5mA until I address it, then it raises to 9mA for a short duration. It is either recognising the command and waking from sleep but giving some weird response or it is not recognising the command at all. Not sure what to try from now.

Graeme

OA47

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Posted: 06:50pm 22 Jun 2017

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Found a bit more information that describes the timing required. It seems the device requires a BREAK of at least 12mS then a MARK at least 8.33mS before the command.
Tried to upload the diagram but it went to black, sorry. Not sure how to achieve this and still maintain the serial port.
Graeme

robert.rozee
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Posted: 07:05pm 22 Jun 2017

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one kludge would be to add a 1k resistor in series with the serial port TxD line. then connect a spare pin of the micromite to the end of the resistor that is away from the micromite.

- when this pin is set as input (default) serial transmission can occur as normal,
- when set to '0' and output, the TxD line will be forced low,
- when set to '1' and output, the TxD line will be forced high,
- when set back to input, serial transmission can resume.

the 1k resistor allows the pin to 'override' the TxD output. the 3mA required to force a different state to the one TxD is in is well within the drive ability of the micromites I/O pins.

cheers,
rob :-)
Edited by robert.rozee 2017-06-24

TassyJim

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Posted: 07:11pm 22 Jun 2017

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This might be a use for peterm's bitbanger csub.

Jim

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OA47

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Posted: 09:18pm 22 Jun 2017

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@Rob
Tried as suggested:

QUERY$(1)=Chr$(255)+Chr$(33) 'ADDRESS QUERY ?!
QUERY$(2)=Chr$(225)+Chr$(33) 'ACKNOWLEDGE ACTIVE a!
QUERY$(3)=Chr$(225)+Chr$(201)+Chr$(33) 'SEND IDENTIFICATION aI!
Open "COM2:1200" As #1
For I=1 To 3
Print Time$; " THE QUERY STRING IS ";QUERY$(I);" ";
Pin(7)=1
Pin(24)=0 'SET THE BREAK >20mS VIA 1K RESISTOR
Pause 20
Pin(24)=1 'SET THE MARK >8.3mS VIA 1K RESISTOR
Pause 10
Pin(24)=0
Print #1, QUERY$(I);
Pause 200
Pin(7)=0
REPLY$=Input$(10,#1)

Print Time$;" THE REPLY STRING IS ";REPLY$
Next I
Close #1

Hope I got the BREAK and MARK the right way round. Had a play round with extending the timings but still no go.

Graeme

OA47

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Posted: 09:28pm 22 Jun 2017

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@Jim
Currently I have the need to interface these devices into the existing 170 chips and I think that Peter's BitBanger Csub is for the 470 chips. Great thought though.
Graeme

TassyJim

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Posted: 09:41pm 22 Jun 2017

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OA47 said @Jim
Currently I have the need to interface these devices into the existing 170 chips and I think that Peter's BitBanger Csub is for the 470 chips. Great thought though.
Graeme

I am using a version of it on the 170 to control some Arlec switches.

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OA47

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Posted: 09:45pm 22 Jun 2017

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I managed to find another copy of the timing diagram:

OA47

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Posted: 09:47pm 22 Jun 2017

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Quote I am using a version of it on the 170 to control some Arlec switches.

Jim is that the one that is labelled for the MM+?

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