Problem interfacing ADXL202 and Accustar Clinometer with 16F876A

[Beatrix]

Hi,

I'm a student learning my way around PICBasic Pro (using a copy
licensed to my school), and I'm having some problems accessing data
via HyperTerminal. Specifically I'm trying to read data from two
AXDL202 accelerometers and one MSI Sensors Accustar Serial Clinometer
being sent to a PIC16F876A. The three sensors send information to one
876A, which transmits the data serially via RF to another 876A, which
I would like to read via Hyperterminal. Unfortunately though, when I
connect to HyperTerminal, I'm not receiving any data, and I have
tested my RF so I know that it is working properly. In addition, I'm
using pins C6 and C7 to connect to the RS232 connectior without a MAX
chip since I seem to recall reading somewhere that those pins can be
used as an internal RS232 buffer to switch the voltage logic.

My code is as follows (I didn't include the initials/variable sections for brevity sake):

First 876A)

accelmeasX1:
pulse_a1x_T2 = 0 'find T2
pulsin xout_a1, 1, pulse_a1x_t1
pulsin xout_a1, 0, temp_x1
pulse_a1x_t2 = pulse_a1x_t2 + temp_x1
pulse_a1x_t2 = pulse_a1x_t2 + pulse_a1x_t1
pulse_a1x_t2 = pulse_a1x_t2 / 10

pulsin xout_a1, 1, pulse_a1x_t1 'read T1

accel1x = (pulse_a1x_t1 / pulse_a1x_t2)
accel1x = accel1x - half_duty
accel1x = accel1x / duty_div
pause 10
goto accelmeasx1

accelmeasY1:
pulse_a1y_T2 = 0 'find T2
pulsin yout_a1, 1, pulse_a1y_t1
pulsin yout_a1, 0, temp_y1
pulse_a1y_t2 = pulse_a1y_t2 + temp_y1
pulse_a1y_t2 = pulse_a1y_t2 + pulse_a1y_t1
pulse_a1y_t2 = pulse_a1y_t2 / 10

pulsin yout_a1, 1, pulse_a1y_t1 'read T1

accel1y = (pulse_a1y_t1 / pulse_a1y_t2)
accel1y = accel1y - half_duty
accel1y = accel1y / duty_div
pause 15
goto accelmeasy1

accelmeasX2:
pulse_a2x_T2 = 0 'find T2
pulsin xout_a2, 1, pulse_a2x_t1
pulsin xout_a2, 0, temp_x2
pulse_a2x_t2 = pulse_a2x_t2 + temp_x2
pulse_a2x_t2 = pulse_a2x_t2 + pulse_a2x_t1
pulse_a2x_t2 = pulse_a2x_t2 / 10

pulsin xout_a2, 1, pulse_a2x_t1 'read T1

accel2x = (pulse_a2x_t1 / pulse_a2x_t2)
accel2x = accel2x - half_duty
accel2x = accel2x / duty_div
pause 20
goto accelmeasx2

accelmeasY2:
pulse_a2y_T2 = 0 'find T2
pulsin yout_a2, 1, pulse_a2y_t1
pulsin yout_a2, 0, temp_y2
pulse_a2y_t2 = pulse_a2y_t2 + temp_y2
pulse_a2y_t2 = pulse_a2y_t2 + pulse_a2y_t1
pulse_a2y_t2 = pulse_a2y_t2 / 10

pulsin yout_a2, 1, pulse_a2y_t1 'read T1

accel2y = (pulse_a2y_t1 / pulse_a2y_t2)
accel2y = accel2y - half_duty
accel2y = accel2y / duty_div
pause 25
goto accelmeasy2


'for tilt #1
init_clin1:
Low TiltReady1
low TiltReq1
If TiltReady1 = 1 then
goto req_clin1
else
goto init_clin1
endif
pause 25

req_clin1:
'while cnt < 17

high TiltReq1
if TiltReady1 = 1 then
goto clin1_prep
else
goto req_clin1
endif

clin1_prep:
if TiltReady1 = 0 then
goto clin1_work
else
goto clin1_prep
endif

clin1_work:
If tiltReady1 = 0 then
tiltreq1 = 0
else
if tiltready1 = 1 then
goto clin1_data
else
goto clin1_work
endif
endif

clin1_data:
high Tiltready1
goto clin1_send

clin1_send:
if tiltready1 = 1 then
Tiltdata1 = clin_data1
goto req_clin1
endif
' cnt = cnt + 1
'wend
goto init_clin1

'for tilt #2
init_clin2:
Low TiltReady2
low TiltReq2
If TiltReady2 = 1 then
goto req_clin2
else
goto init_clin2
endif
pause 25

req_clin2:
'while cnt2 = 17

high TiltReq2
if TiltReady2 = 1 then
goto clin2_prep
else
goto req_clin2
endif

clin2_prep:
if TiltReady2 = 0 then
goto clin2_work
else
goto clin2_prep
endif

clin2_work:
If tiltReady2 = 0 then
tiltreq2 = 0
else
if tiltready2 = 1 then
goto clin2_data
else
goto clin2_work
endif
endif

clin2_data:
high Tiltready2
goto clin2_send

clin2_send:
if tiltready2 = 1 then
Tiltdata2 = clin_data2
goto req_clin2
endif
' cnt2 = cnt2 + 1
' wend
goto init_clin2

btnclk:
'for buttons
Clk_str1 = 0
clk_str2 = 0

if click1 = 1 then
clk_str1 = 1
else
clk_str1 = 0
endif

if click2 = 1 then
clk_str2 = 1
else
clk_str2 = 0
endif
goto btnclk

Send_Data:
'for sending to tx
serout porta.0, n9600, ["ATJHSD"]
serout porta.0, n9600, [accel1x]
pause 5
serout porta.0, n9600, ["BSDFGF"]
serout porta.0, n9600, [accel1y]
pause 5
serout porta.0, n9600, ["CTERT"]
serout porta.0, n9600, [accel2x]
pause 5
serout porta.0, n9600, ["DDFGHT"]
serout porta.0, n9600, [accel2y]
pause 5
serout porta.0, n9600, ["EVBNRG"]
serout porta.0, n9600, [clin_data1]
pause 5
serout porta.0, n9600, ["FPOEQUY"]
serout porta.0, n9600, [clin_data2]
pause 5
serout porta.0, n9600, ["GGHBDG"]
serout porta.0, n9600, [clk_str1]
pause 5
serout porta.0, n9600, ["HDFYEB"]
serout porta.0, n9600, [clk_str2]
pause 5
goto send_data

end


Second 876A)

incoming:
serin portb.0, n9600, 1000, ser_error, ["ATJHSD"], Accel1x
pause 5
serin portb.0, n9600, 1000, ser_error, ["BSDFGF"], Accel1y
pause 5
serin portb.0, n9600, 1000, ser_error, ["CTERT"], Accel2x
pause 5
serin portb.0, n9600, 1000, ser_error, ["DDFGHT"], Accel2y
pause 5
serin portb.0, n9600, 1000, ser_error, ["EVBNRG"], Clin_data1
pause 5
serin portb.0, n9600, 1000, ser_error, ["FPOEQUY"], Clin_data2
pause 5
serin portb.0, n9600, 1000, ser_error, ["GGHBDG"], Clk_str1
pause 5
serin portb.0, n9600, 1000, ser_error, ["HDFYEB"], Clk_str2
pause 5

ser_error:
pause 1000
goto incoming

calc_accel1: 'using pyth triangle
Accel1x = Accel1x * accel1x
accel1y = accel1y * accel1y
accel_1 = accel1x + accel1y
accel_1 = sqr(accel_1)

calc_accel2: 'using pyth triangle
accel2x = accel2x * accel2x
accel2y = accel2y * accel2y
accel_2 = accel2x + accel2y
accel_2 = sqr(accel_2)

calc_pos1: 'x=(1/2)at^2
time = 5
time = time * time
half = 1 / 2
pos1 = half * Accel_1
pos1 = pos1 * time

'if pos > ? then



calc_pos2:
time = 5
time = time * time
pos2 = half * Accel_2
pos2 = pos2 * time


send_data:
serout portc.7, n9600, ["M"]
serout portc.7, n9600, [Accel_1]
pause 5
serout portc.7, n9600, [Accel_2]
pause 5
serout portc.7, n9600, [Clin_data1]
pause 5
serout portc.7, n9600, [clin_data2]
pause 5
serout portc.7, n9600, [pos1]
pause 5
serout portc.7, n9600, [pos2]
pause 5
goto send_data

end



As I said, I'm still learning PBP, so I'm sure that my problem of not
reading any data in HyperTerminal could very well be a gross error
I'm making (I'm using Hellebuyck's PIC Microcontrollers book as a reference). I
was hoping that someone here could point me in the right direction
please? Sorry if this is a simple problem, but I just can't seem to
figure it out.

Thanks!

[mister_e]

As you use MAX ic, you don't need to use N9600... use T9600 instead

But that will not solve your problem with Hyperterminal. There's for sure a way to make that software work but i never spend the time to work with. I prefer to use MicroCode Studio to edit my code and use the Serial Communicator window. It's so easy to use.

you download the free version of MicroCode Studio here

more info
here

[Beatrix]

Thanks, I'll try Microcode Studio later when I'm able to. Oh, and I'm NOT using the MAX IC, so I think I need to use N9600....right?

[mister_e]

You're right. With a resistor in serie that will work.

[Beatrix]

You're right. With a resistor in serie that will work.

Hmm..that might be part of my problem. Right now I have pin C6 connected to pin 3 of the RS232 connector and pin C7 connected to pin 2 directly (no resistor in series). What resistor would you recomend? That and would I need to use any of the other pins on the RS232 connector (request to send, etc) if just reading trhe data via HyperTerminal or Microsode Studio?

[NavMicroSystems]

Hmm..that might be part of my problem. Right now I have
pin C6 connected to pin 3 of the RS232 connector and
pin C7 connected to pin 2 directly (no resistor in series). What resistor would you recomend?
That and would I need to use any of the other pins on the RS232 connector (request to send, etc) if just reading trhe data via HyperTerminal or Microsode Studio?

Beatrix,

On the second PIC (I guess that's the one to transfer data to the PC) you are using PortB.0 with SERIN
I assume that's the incomming Data from the first PIC.

And you are using PortC.7 with SEROUT
I assume that's the outgoing Data to the PC.
A series resistor is not really required on the PC's RX-Pin.
(But 1k wouldn't hinder either)

Since the PIC does not receive any Data from the PC
you don't need a connection between PortC.6 and Pin3 on the RS232.
If you want to connect it you should have a series resistor (say 22k).

All you actually need are two wires:
PortC.7 to RS232 Pin 2
and
PIC GND (Vss) to RS232 Pin 5

Is it probably the missing GND that is causing the Problem?

Set the Handshake in Hyperterm to "NONE"

Simple test of your PCs serial Port:
With nothing connected to the RS232
In Hyperterm set "Local Echo" to "OFF"
when type on your keyboard there should nothing appear on your screen.

Now connect Pin 2 and Pin 3 on the RS232
every character typed should be echoed back on the screen.

[Beatrix]

Regarding the connection to ground: currently I have both of the Vss pins connected to board ground. For this connection to RS232 ground, should I simply solder in a wire, thereby having Vss connected to board ground and RS232 ground, or should I disconnect it from board ground and only connect it to RS232 ground?

[NavMicroSystems]

...having Vss connected to board ground and RS232 ground...

That's the way it should be.

[Beatrix]

I tried it again with the ground wire in place and no more receive wire using both Microcode Studio and HyperTerminal, and it still doesn't work. Is there anything I should be doing with the other pins on the RS232 connector? Any ideas?

[NavMicroSystems]

Beatrix,

have you tried the simple test described here

Have you set the Baudrate on the PC-side correctly
and is "Handshake" set to none?

Could you post a schematic and your code (cut down to the RS232 part)

For a one-way communication (PIC --> PC) you definitely need only two wires:
PIC-GND to PC-GND and PTC-TX to PC-RX

Probably your PCs COM-Port doesn't work with TTL-Levels.
If so you would need to add a MAX232-type of Level shifter.

[Beatrix]

For that test, would I need to use an RS232 keyboard? I didn't run it since I'm pretty sure the port works since I'm also using it to program my PICs. The baudrate and handshake is set on the PC as well.

I'll probably have to try it with another computer to see if the one I'm using is not compatible and needs the MAX IC. That's going to be a problem since the board had been fabricated and adding the MAX would require me to do a bit of a workaround (which is why I'm trying to get it going without the MAX). Initially, I was planning on using a PS/2 connection to transmit the data to the computer, but I was unable to find enough information on it to the point that I could understand how it works, so I decided to switch to RS232.

[NavMicroSystems]

For that test, would I need to use an RS232 keyboard?

All you need is a simple piece of wire betwenn Rx and Tx on the PCs RS232

I didn't run it since I'm pretty sure the port works since I'm also using it to program my PICs. The baudrate and handshake is set on the PC as well.

Well that case I would assume the PCs RS232 isfunctional, but not compatible with the PICs Levels.

Anyway
If you want to make sure your Product works with any PC-COM-Port you should add a Levelshifter.

The PICs (0/+5V) Levels are ways off the specs of a standard COM-Port (+/- 12V)

And bear in mind: the MAX232 does not only shift the levels, it also inverts the logic.