BS2p40 Interpertor Chip and MAX202 serial IC
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I have a BS2p40 interperter IC on a custom board and I have RA2 and
RA3 of the interperter going to a MAX202 serial IC and I can't
communicate with the interperter IC. I am using the MAX202 to do the
level shifting to RS232 serial levels. Will this work? I have used
these Maxim parts in the past to interface from the output pin of a
stamp before and it worked but this is the first time trying to
communicate with the basic interperter to try to program it. The
oscillator is wiggling, Vdd and ground check out and there are no
shorts between any of the pins of the SX48 part.
Jason
RA3 of the interperter going to a MAX202 serial IC and I can't
communicate with the interperter IC. I am using the MAX202 to do the
level shifting to RS232 serial levels. Will this work? I have used
these Maxim parts in the past to interface from the output pin of a
stamp before and it worked but this is the first time trying to
communicate with the basic interperter to try to program it. The
oscillator is wiggling, Vdd and ground check out and there are no
shorts between any of the pins of the SX48 part.
Jason
Comments
>RA3 of the interperter going to a MAX202 serial IC and I can't
>communicate with the interperter IC. I am using the MAX202 to do the
>level shifting to RS232 serial levels. Will this work? I have used
>these Maxim parts in the past to interface from the output pin of a
>stamp before and it worked but this is the first time trying to
>communicate with the basic interperter to try to program it. The
>oscillator is wiggling, Vdd and ground check out and there are no
>shorts between any of the pins of the SX48 part.
>Jason
Hi Jason,
You didn't mention having a connection to the MCLR\ pin on the SX48.
That is required for programming. From pin 4 of the DB9S (DTR), to an
inverter, to pin 1 (MCLR\) on the SX48.
Also, there should be a connection from pin 6 to pin 7 on the DB9.
Also, the transistor circuit that is used for the RS232 interface on
the Stamp 2 series has a side effect; it passively echos all received
characters back to the PC. AFAIK the programming software expects to
hear that passive echo (but I'm not sure if lack of the echo would
lead to the "stamp not found" error.)
-- regards,
Tracy Allen
electronically monitored ecosystems
mailto:tracy@e...
http://www.emesystems.com
tied to VCC with a 10k pullup and to ATN through the MAX202. I need
to see it this is going low when I attempt to communicate to it. I
assume MCLR\ needs to be pulled low while being programed. As for the
echo I could try a 4.7k resistor between pins 2 and 3 of the DB9.
Jason
--- In basicstamps@y..., Tracy Allen <tracy@e...> wrote:
> >I have a BS2p40 interperter IC on a custom board and I have RA2 and
> >RA3 of the interperter going to a MAX202 serial IC and I can't
> >communicate with the interperter IC. I am using the MAX202 to do
the
> >level shifting to RS232 serial levels. Will this work? I have used
> >these Maxim parts in the past to interface from the output pin of a
> >stamp before and it worked but this is the first time trying to
> >communicate with the basic interperter to try to program it. The
> >oscillator is wiggling, Vdd and ground check out and there are no
> >shorts between any of the pins of the SX48 part.
> >Jason
>
> Hi Jason,
>
> You didn't mention having a connection to the MCLR\ pin on the
SX48.
> That is required for programming. From pin 4 of the DB9S (DTR), to
an
> inverter, to pin 1 (MCLR\) on the SX48.
>
> Also, there should be a connection from pin 6 to pin 7 on the DB9.
>
> Also, the transistor circuit that is used for the RS232 interface
on
> the Stamp 2 series has a side effect; it passively echos all
received
> characters back to the PC. AFAIK the programming software expects
to
> hear that passive echo (but I'm not sure if lack of the echo would
> lead to the "stamp not found" error.)
>
> -- regards,
> Tracy Allen
> electronically monitored ecosystems
> mailto:tracy@e...
> http://www.emesystems.com
>tied to VCC with a 10k pullup and to ATN through the MAX202. I need
>to see it this is going low when I attempt to communicate to it. I
>assume MCLR\ needs to be pulled low while being programed. As for the
>echo I could try a 4.7k resistor between pins 2 and 3 of the DB9.
>Jason
Hi Jason,
ATN goes high briefly (MCLR\ low) at the very start of the
programming, and then again at the very end.
To get the echo, you'd also need a diode in series with the TX pin on
your MAX202, to make a wired-OR connection:
tx 3 >
o
Sin
4.7k |
DB9 ;--/\/\----' BS2
| 1n4748
rx 2 <--o
|<
Sout
-- regards,
Tracy Allen
electronically monitored ecosystems
mailto:tracy@e...
http://www.emesystems.com
I used the circuit that Parallax uses for level shifting the serial
into the Scenix IC. That worked. I used 2 3904's and a 3906 with a
bunch a 10k resistors. I think the problem is that the logic is
inverted as it is level shifted through the transistor and the BS
interperter is programed for this. If I add inverters to the MAX202
circuit it would probably work but I have no room left on the board
for this - even if I used SOT 23-5 inverters. The MAX202 will have to
go.
Jason
--- In basicstamps@y..., Tracy Allen <tracy@e...> wrote:
> >I need to take some scope plots to see whats going on. I do have
MCLR\
> >tied to VCC with a 10k pullup and to ATN through the MAX202. I need
> >to see it this is going low when I attempt to communicate to it. I
> >assume MCLR\ needs to be pulled low while being programed. As for
the
> >echo I could try a 4.7k resistor between pins 2 and 3 of the DB9.
> >Jason
>
> Hi Jason,
>
> ATN goes high briefly (MCLR\ low) at the very start of the
> programming, and then again at the very end.
>
> To get the echo, you'd also need a diode in series with the TX pin
on
> your MAX202, to make a wired-OR connection:
>
> tx 3 >
o
Sin
> 4.7k |
> DB9 ;--/\/\----' BS2
> | 1n4748
> rx 2 <--o
|<
Sout
>
> -- regards,
> Tracy Allen
> electronically monitored ecosystems
> mailto:tracy@e...
> http://www.emesystems.com