Tool/software:
Hi, I've recently been using an ADS1278v2EVM to capture data to my Raspberry Pi 4b, via SPI communication.
I saw someone else doing this, and there is a case that provides part of the wiring and code reference, I tried to follow his line of thought, but I have a problem that I can't solve: I don't know what causes, I can't read the data, I'll explain in detail my understanding of the problem below;
Very much hope you can give me some help.
After power on, the three power indicator lights are green and normal state.
Now the problem is: I can't collect the data;In the SPI protocol, DRDY goes high once SYNC goes low; DRDY stays high after SYNC returns high, and goes low once it is done retrieving valid data; after troubleshooting and testing, the code is stuck at “DRDY doesn't output a falling edge”.
The wiring between my ADS1278V2EVM and the Raspberry Pi is shown below:
J6 (The middle two columns correspond to the J6 pins of the ADS1278V2EVM, and the left and right columns correspond to the pins of the Raspberry Pi)
| 22：GPIO6 | FSDY | SCLK | SCLK |
|---|---|---|---|
| 32：GPIO26 | CLK | DO1 | MISO |
| 0 | DO2 | DO3 | 0 |
| 0 | DO4 | DO5 | 0 |
| 0 | DO6 | DO7 | 0 |
| 0 | DO8 | DIN | |
| 16：GPIO1 | SYNC | EEWP | 不接（原因未知） |
| GND | GND | GND |
J4 (High Speed, SPI, TDM, Fixed Mode, Clock Input Divided to High Speed selected here)
| M0 | M1 | F0 | F1 | F2 | CLKDIV |
|---|---|---|---|---|---|
| 0：open | 0：open | 1：short | 0：open | 0：open | 1：short |
| JP1——3 | JP2——3 |
|---|---|
| JP1——2 | JP2——2 |
| OPEN——1 |
My code is:
import RPi.GPIO as GPIO
import spidev
# SPI setting
spi = spidev.SpiDev()
spi.open(0,0) # spi.open(bus,device)，连接到指定设备
spi.max_speed_hz = 7800000 # SCLK frequency 根据树莓派SPI速度列表
spi.mode = 0b00 # C_POL=0, C_PHA=0；SCLK空闲时为低电平，第一个时间沿采样；
spi.no_cs = True # 设置SPI_NO_CS标志是否使用CS，此处使用CS
# get bytes
def adc_1ch(): # 1channel
data = spi.xfer([0x00,0x00,0x00]) # 24bits = 3bytes，读取
adc = (data[0] << 16) + (data[1] << 8) + data[2] # shift register，将data24字节的数据转化为数值
if adc > (2**23-1): # 2's complement
adc = adc - 2**24
voltage = (adc*2.5)/(2**23 - 1) # 此处参考电压是V（REF） = 2.5V，
return voltage
def adc_8ch(): # 8channel
ch = []
for i in range(8):
ch.append(adc_1ch())
return ch
# GPIO setting，将SYNC和CLK都设为1，高电平
# 该函数将GPIO引脚22设置为输入模式，并将其状态设置为高电平。
GPIO.setmode(GPIO.BOARD)
pins = [16, 32] # 物理接口
# SYNC, CLK Select pin
volt = [1,1] # 1=high, 0=low
for p in range(2):
GPIO.setup(pins[p],GPIO.OUT)
if volt[p] == 1:
GPIO.output(pins[p],GPIO.HIGH)
else:
GPIO.output(pins[p],GPIO.LOW)
# （新款PCB板可以通过跳线设置高低电平，所以此处只有SYNC和CLK需要编程实现高低电平）
GPIO.setup(22,GPIO.IN) # DRDY pin 该函数将GPIO引脚22设置为输入模式，并将其状态设置为高电平。
# main
i = 0 # timer
while True: # loop 100 times
GPIO.wait_for_edge(22, GPIO.FALLING) # start to capture data when DRDY falling down
print(adc_8ch()) # capture data
i = i + 1
if i == 100: # timer stop
break
GPIO.cleanup()
