Bit banging an MCP3008 with pigpio bb_spi returns all 1023s

Question

I started to try to read an MCP3008 ADC using SPI bit banging with pigpio. I wrote the unattractive little script below, starting from the example in the pigpio documentation and here is a screenshot of my output.

I believe that this should read the lowest four channels of the ADC and print the output. Channels 0 to 3 are connected to +5V, GND, +5V, floating, so I expected to see values like 1023, 0, 1023, xxx where the last would be noise.

Instead I see all 1023's.

Have I done something terribly wrong?

import pigpio
import time

CE1  = 2
MISO = 3
MOSI = 4
SCLK = 17

pi = pigpio.pi()

pi.bb_spi_open(CE1, MISO, MOSI, SCLK, 10000, 3)

nums = [128 + n for n in (16, 32, 48, 64)]
while True:
    print "wow!"
    for num in nums:
        print "num! ", num
        count, data = pi.bb_spi_xfer(CE1, [1, num, 0])

        print "count = ", count, data = [byte for byte in data]

        value = ((data[1]&3)<<8) | data[2]
        print "value = ", value
        time.sleep(1)

Answer 1

Comments by @Joan (above) were extremely helpful! MCP3008 does indeed use mode=0, where I had it erroneously set to 3.

The following works very nicely!

import pigpio
import time

CS   = 2
MISO = 3
MOSI = 4
SCLK = 17
MODE = 0

pi = pigpio.pi()

pi.bb_spi_close(CS)  # because I use ctrl-C to break each time

pi.bb_spi_open(CS, MISO, MOSI, SCLK, 10000, MODE)

while True:
    for n in range(4):

        ct, data = pi.bb_spi_xfer(CS, [1, (8+n)<<4, 0])

        val  = ((data[1]<<8) | data[2]) & 0x3FF

        print (n, ct, val, "data=", [byte for byte in data] )

    time.sleep(1)