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器件型号：ADS1220 工具/软件：
大家好！
我希望你很好,并准备好帮助我;-)
我尝试将 ADS1220（CJMCU-1220 品牌）连接 到 Raspberry Pi 4B、然后借助 可编程电源对其进行测试（在差分 A0A1 中）。 我可以通过一个万用表 Keithley 2701 来检查真实的张力。
我的 布线如下：
Raspberry Pi ADS1220 ----------------- ------------- 3.3V (Pin 1) ---> AVDD (Pin 8), DVDD (Pin 6) GND (Pin 6) ---> AGND (Pin 9), DGND (Pin 7) MOSI (Pin 19) ---> MOSI (Pin 3) MISO (Pin 21) ---> MISO (Pin 2) SCLK (Pin 23) ---> SCLK (Pin 4) CE0 (Pin 24) ---> CS (Pin 5) GPIO17 (Pin 11) ---> DRDY (Pin 1)
我使用的代码是：
import spidev
import RPi.GPIO as GPIO
import time
import csv
import os
from datetime import datetime
# Raspberry Pi pins connected to the ADS1220
CS_PIN = 8 # Chip Select (GPIO8/CE0)
DRDY_PIN = 17 # Data Ready (GPIO17)
# SPI configuration
SPI_BUS = 0
SPI_DEVICE = 0
SPI_SPEED_HZ = 1000000 # 1 MHz
# ADS1220 commands
CMD_RESET = 0x06
CMD_START = 0x08
CMD_POWERDOWN = 0x02
CMD_RDATA = 0x10
CMD_WREG = 0x40
CMD_RREG = 0x20
# ADS1220 registers
REG_CONF0 = 0x00
REG_CONF1 = 0x01
REG_CONF2 = 0x02
REG_CONF3 = 0x03
# Conversion parameters
VREF = 2.048 # Volts (internal reference of ADS1220)
FSR = (2**23) # Full scale range (24 bits with 1 sign bit)
CSV_FILENAME = "ads1220_data.csv"
def ask_gain():
print("Choose the gain for the ADS1220:")
print(" 1 : Gain = 1")
print(" 2 : Gain = 2")
print(" 4 : Gain = 4")
print(" 8 : Gain = 8")
print("16 : Gain = 16")
print("32 : Gain = 32")
print("64 : Gain = 64")
print("128: Gain = 128")
valid_gains = [1,2,4,8,16,32,64,128]
while True:
try:
g = int(input("Enter the desired gain value: "))
if g in valid_gains:
return g
else:
print("Invalid value. Try again.")
except Exception:
print("Invalid input. Try again.")
def wait_drdy():
cpt = 0
while GPIO.input(DRDY_PIN):
time.sleep(0.001)
cpt += 1
if cpt % 1000 == 0:
print(f"[DEBUG] Still waiting for DRDY ({cpt} ms)")
def ads1220_write_reg(spi, reg, value):
spi.xfer2([CMD_WREG | (reg << 2), 0x00, value])
def ads1220_read_reg(spi, reg):
resp = spi.xfer2([CMD_RREG | (reg << 2), 0x00, 0x00])
return resp[2]
def ads1220_read_data(spi):
resp = spi.xfer2([CMD_RDATA, 0x00, 0x00, 0x00])
raw = (resp[1] << 16) | (resp[2] << 8) | resp[3]
if raw & 0x800000:
raw -= 1 << 24
return raw
def ads1220_init(spi, gain):
# Converter reset
spi.xfer2([CMD_RESET])
time.sleep(0.1)
# MUX[3:0]=0000 (A0-A1), PGA enabled, user-selected gain
mux_bits = 0b0000 << 4
pga_enable = 0 << 3
# GAIN bits (2:0), according to table
gain_map = {
1: 0b000,
2: 0b001,
4: 0b010,
8: 0b011,
16: 0b100,
32: 0b101,
64: 0b110,
128: 0b111
}
gain_bits = gain_map[gain]
reg0 = mux_bits | pga_enable | gain_bits
reg1 = 0b00000000 # Data rate=20SPS, normal mode, single-shot conversion
reg2 = 0b00010000 # Internal VREF, 50/60Hz rejection
reg3 = 0x00 # Disable IDACs
ads1220_write_reg(spi, REG_CONF0, reg0)
ads1220_write_reg(spi, REG_CONF1, reg1)
ads1220_write_reg(spi, REG_CONF2, reg2)
ads1220_write_reg(spi, REG_CONF3, reg3)
# Register debug
val0 = ads1220_read_reg(spi, REG_CONF0)
print(f"[DEBUG] REG0 after init : {bin(val0)} (0x{val0:02X}), gain={gain}")
def raw_to_voltage(raw):
v = (raw / float(FSR)) * (VREF)
return v
def append_to_csv(filename, row):
file_exists = os.path.isfile(filename)
with open(filename, 'a', newline='') as csvfile:
writer = csv.writer(csvfile, delimiter=';')
if not file_exists:
writer.writerow(['Timestamp', 'Raw_value', 'Diff_voltage_V', 'Gain'])
writer.writerow(row)
def get_timestamp():
return datetime.now().strftime("%d/%m/%y - %H:%M:%S")
def main():
print("[DEBUG] GPIO initialization")
GPIO.setmode(GPIO.BCM)
GPIO.setup(DRDY_PIN, GPIO.IN)
gain = ask_gain()
print(f"[DEBUG] SPI initialization (bus={SPI_BUS}, device={SPI_DEVICE}, speed={SPI_SPEED_HZ} Hz)")
spi = spidev.SpiDev()
spi.open(SPI_BUS, SPI_DEVICE)
spi.max_speed_hz = SPI_SPEED_HZ
spi.mode = 1
ads1220_init(spi, gain)
try:
while True:
spi.xfer2([CMD_START])
wait_drdy()
value_raw = ads1220_read_data(spi)
value_volts = raw_to_voltage(value_raw)
timestamp = get_timestamp()
print(f"{timestamp} ; {value_raw} ; {value_volts:.6f} ; {gain}")
append_to_csv(CSV_FILENAME, [timestamp, value_raw, f"{value_volts:.6f}", gain])
time.sleep(1)
finally:
print("[DEBUG] Closing SPI and cleaning up GPIO")
spi.close()
GPIO.cleanup()
if __name__ == '__main__':
main()
问题在于、读寄存器函数（行 112：val0 = ads1220_read_reg(SPI, REG_CONF0)) 总是返回“0b11111111 (0xFF)“、而不是像“0b000000000000"。“。
我已经检查了 Raspberry Pi 的 SPI 通信功能并运行良好。
我必须承认、我不知道这是硬件问题还是软件问题、还是两者兼而有...
我希望你能帮我！
提前感谢您！
SU
