Up to date driver for MAX1202 A/D chip

Rsadeika

Does anybody have an updated driver for the MAX1202 chip? Since I am destroying my electronics stuff (Activity Board) with my latest experiments, I am going a cheaper route, individual parts. I dug out my old Propeller Platform Board and I found a MAX1202 chip. I will breadboard the MAX1202 and if something goes wrong, it will cost me less than $10.00 which include a Propeller chip, I think.

I would prefer a C driver, this is a big stretch, but I would be very happy with Spin driver. I did find a driver in the OBEX, but it relies on a BS2 object, the last time I worked with a BS2 was probably 10 or 15 years ago, not sure if I want to go backwards. Hopefully somebody has something that is the latest.

Thanks

Ray

Publison

Don't be afraid of the BS2 Functions. Martin wrote that object to make BS2 users to be comfortable with SPIN.

For example, the call to

bs2.SHIFTOUT(AoutAdc, ClkAdc, Value2Pass, BS2#MSBFIRST,8 )

just does this in SPIN

PUB SHIFTOUT (Dpin, Cpin, Value, Mode, Bits)| bitNum
{{
   Shift data out, master clock, for mode use ObjName#LSBFIRST, #MSBFIRST
   Clock rate is ~16Kbps.  Use at 80MHz only is recommended.
     BS2.SHIFTOUT(5,6,"B",BS2#LSBFIRST,8)
}}
    outa[Dpin]:=0                                          ' Data pin = 0
    dira[Dpin]~~                                           ' Set data as output
    outa[Cpin]:=0
    dira[Cpin]~~

    If Mode == LSBFIRST                                    ' Send LSB first    
       REPEAT Bits
          outa[Dpin] := Value                              ' Set output
          Value := Value >> 1                              ' Shift value right
          !outa[Cpin]                                      ' cycle clock
          !outa[Cpin]
          waitcnt(1000 + cnt)                              ' delay

    elseIf Mode == MSBFIRST                                ' Send MSB first               
       REPEAT Bits                                                                
          outa[Dpin] := Value >> (bits-1)                  ' Set output           
          Value := Value << 1                              ' Shift value right    
          !outa[Cpin]                                      ' cycle clock          
          !outa[Cpin]                                                             
          waitcnt(1000 + cnt)                              ' delay                
    outa[Dpin]~                                            ' Set data to low

You can get rid of the BS2 object, and just use to SPIN code for the Shiftout.

Rsadeika

Thanks Publison, it does not look like there are too many people using the MAX1202. I will give the existing object a try and see what happens. There is also spin2cpp available to convert it too C if I find this to be handy, not sure where this will end up.

Ray

Rsadeika

After looking at the MAX1202 object, the first stumbling block, wiring up to the chip. Below is the chart for the Spin pin requirements and the MAX1202 pin usage. Some are obvious while others, not so.

Spin - Max1202
5 - 18
3 - 16
Not sure about the rest of them, if somebody could enlighten me, would be appreciated.

Ray

Spin program CON
ClkAdc = 11 ' A/D clock (Change These Values/Pins As Needed)
CsAdc = 5 ' Chip Select for ADC
AoutAdc = 13 ' A/D Data sent to the ADC
AinAdc = 12 ' A/D Data recieved from the ADC
Sstrb = 3 ' SSTRB signal for max 1202
ready = 16 ' Cog ready signal (pin to read for ready state)


PIN NAME FUNCTION
1–8 CH0–CH7 Sampling Analog Inputs
9 VSS Negative Supply Voltage. Tie VSS to -5V ±5% or to GND.
10 SHDN Three-Level Shutdown Input. Pulling SHDN low shuts the MAX1202/MAX1203 down to 10μA (max)
supply current; otherwise, the MAX1202/MAX1203 are fully operational. Pulling SHDN to VDD puts
the reference-buffer amplifier in internal compensation mode. Leaving SHDN unconnected puts the
reference-buffer amplifier in external compensation mode.
11 REF Reference-Buffer Output/ADC Reference Input. In internal reference mode (MAX1202 only), the
reference buffer provides a 4.096V nominal output, externally adjustable at REFADJ. In external
reference mode, disable the internal buffer by pulling REFADJ to VDD.
12 REFADJ Input to the Reference-Buffer Amplifier. Tie REFADJ to VDD to disable the reference-buffer amplifier.
13 GND Ground; IN- Input for Single-Ended Conversions
14 VL Supply Voltage for Digital Output Pins. Voltage applied to VL determines the positive output swing of
the Digital Outputs (DOUT, SSTRB). 2.7V ≤ VL ≤ 5.25V.
15 DOUT Serial-Data Output. Data is clocked out at SCLK’s falling edge. High impedance when CS is high.
16 SSTRB Serial-Strobe Output. In internal clock mode, SSTRB goes low when the MAX1202/MAX1203 begin
the analog-to-digital conversion, and goes high when the conversion is finished. In external clock
mode, SSTRB pulses high for one clock period before the MSB decision. High impedance when CS is
high (external clock mode).
17 DIN Serial-Data Input. Data is clocked in at SCLK’s rising edge.
18 CS Active-Low Chip Select. Data is not clocked into DIN unless CS is low. When CS is high, DOUT is
high impedance.
19 SCLK Serial-Clock Input. SCLK clocks data in and out of the serial interface. In external clock mode, SCLK
also sets the conversion speed (Duty cycle must be 40% to 60% in external clock mode).
20 VDD Positive Supply Voltage, +5V ±5%

kwinn

Propeller > MAX1202

ClkAdc = 11 > 19 ' A/D clock (Change These Values/Pins As Needed)
CsAdc = 5 > 18 ' Chip Select for ADC
AoutAdc = 13 > 17 ' A/D Data sent to the ADC
AinAdc = 12 > 15 ' A/D Data received from the ADC
Sstrb = 3 > 16 ' SSTRB signal for max 1202
ready = 16 > ?? ' Cog ready signal (pin to read for ready state)

?? - Not sure where this connects. Could be the SHDN, it is the only control signal not accounted for, but I do not have time to hunt through the code to find it.

Pin 14 is the low voltage power input and should be connected to 3.3V if you want to connect the ADC pins directly to the propeller pins. If you connect +5V here you will need protection resistors for propeller input pins.

You can download the data sheet here if you do not have it already. http://www.maximintegrated.com/en/products/analog/data-converters/analog-to-digital-converters/MAX1202.html/tb_tab2

Rsadeika

Thanks kwinn, I went through the code and could not find how or where it uses "ready = 16 > ?? ' Cog ready signal (pin to read for ready state)". This particular program by James Long seems to be a specialized program for reading Altitude and Airspeed instruments. Not sure how I could use this program to do Voltage readings @ ~20V. In the chip documentation it mentions something about a 4.096V as reference, so that means I would have to reconfigure all my resister values, I think I will turn back the clock and make it so I did not find that chip.

So now I have two choices, use my PropBOE board or use my C3 board, which one is expendable? The PropBOE has some code for doing voltages, but the code would need to be changed to suit my purposes, this is Spin code, now I am used to working with C. I believe the same thing is true with the C3, would have to make code changes to make it work for me.

Ray

kwinn

Those are pretty expensive boards to risk frying. A protoboard would be much less, and a dip prop chip in a socket on a small pad per hole pcb is about a third of that. Another idea would be to build a 3.3V to 5V buffer board to go between the propeller and circuit under development.