Hi NXP community,
I'm struggling with basic communication on a PCA9745B. Reading MODEs 1 and 2 works fine, and I get 0 and 1 as outputs, respectively.
However, anything beyond that gets... strange. For example, reading register 02h (LEDOUT0) after either a RESET or power down/power up gives FFh; it should be AAh, if I understand the defaults correctly. Even stranger, writing AAh to the LEDOUT0 register followed by a read gives 0. If I read again, with no changes, I again get FFh. I have confirmed that all four signals (CS/SCLK/MOSI/MISO) act as they should with an oscilloscope.
Commands look like this:
send_SPI([0b00000101,0b11111111]) #set up to read register 10
send_SPI([0b11111111,0b11111111]) #read out result
printed result: [0,FFh]
send_SPI([0b00000100,0b10101010]) #wire 10 to LED0 through LED 3
send_SPI([0b00000101,0b11111111]) #set up to read register 10
test = send_SPI([0b11111111,0b11111111])
printed result: [0,0]
send_SPI([0b00000101,0b11111111]) #set up to read register 10
test = send_SPI([0b11111111,0b11111111])
printed result: [0,FFh]
Pins:
1) R = 910Ohms (to ground)
2) gnd
3) MISO
4) CS
5) gnd
6) Green LED cathode
7) NC
8) NC
9) NC
10) gnd
11) NC
12) NC
13) NC
14) NC
15) NC
16) NC
17) NC
18) NC
19) gnd
20) NC
21) NC
22) NC
23) NC
24) gnd
25) 10k pull up resistor to +5V
26) SCLK
27) MOSI
28) +5V
Any ideas why this might be happening? I'm happy to share scope readings, code, diagrams, etc. if any additional information would be useful. Thank you in advance!
Cheers,
Dan
