diff --git a/third_party/mfrc522_integration/mfrc522_rp2040_integration.c b/third_party/mfrc522_integration/mfrc522_rp2040_integration.c
index c3b4bee..f9cbeea 100644
--- a/third_party/mfrc522_integration/mfrc522_rp2040_integration.c
+++ b/third_party/mfrc522_integration/mfrc522_rp2040_integration.c
@@ -45,12 +45,35 @@
 #include "driver_mfrc522_interface.h"
 
 #define MFRC522_CFG_RST_GPIO         9
+#define MFRC522_CFG_SPI_INSTANCE    spi1
 #define MFRC522_CFG_SPI_MISO_GPIO   12
 #define MFRC522_CFG_SPI_MOSI_GPIO   11
 #define MFRC522_CFG_SPI_CLK_GPIO    10
 #define MFRC522_CFG_SPI_SS_GPIO     13
 #define MFRC522_CFG_SPI_SPEED_MHZ   (1000 * 1000)
 
+/**
+ * @brief Helper function to pull the CS line low
+ *
+ * Taken from pico-examples, bme280_spi.c
+ */
+static inline void cs_select() {
+    asm volatile("nop \n nop \n nop");
+    gpio_put(MFRC522_CFG_SPI_SS_GPIO, 0);  // Active low
+    asm volatile("nop \n nop \n nop");
+}
+
+/**
+ * @brief Helper function to release the CS line low
+ *
+ * Taken from pico-examples, bme280_spi.c
+ */
+static inline void cs_deselect() {
+    asm volatile("nop \n nop \n nop");
+    gpio_put(MFRC522_CFG_SPI_SS_GPIO, 1);
+    asm volatile("nop \n nop \n nop");
+}
+
 /**
  * @brief  interface reset gpio init
  * @return status code
@@ -164,14 +187,19 @@ uint8_t mfrc522_interface_spi_init(void)
     gpio_set_function(MFRC522_CFG_SPI_MISO_GPIO, GPIO_FUNC_SPI);
     gpio_set_function(MFRC522_CFG_SPI_MOSI_GPIO, GPIO_FUNC_SPI);
     gpio_set_function(MFRC522_CFG_SPI_CLK_GPIO, GPIO_FUNC_SPI);
-    gpio_set_function(MFRC522_CFG_SPI_SS_GPIO, GPIO_FUNC_SPI);
+    //gpio_set_function(MFRC522_CFG_SPI_SS_GPIO, GPIO_FUNC_SPI);
+    //gpio_set_dir(MFRC522_CFG_SPI_CLK_GPIO, GPIO_OUT);
+
+    gpio_init(MFRC522_CFG_SPI_SS_GPIO);
+    gpio_set_dir(MFRC522_CFG_SPI_SS_GPIO, GPIO_OUT);
+    gpio_put(MFRC522_CFG_SPI_SS_GPIO, 1);
 
     /*
      * From the manual:
      * "There is no guarantee that the baudrate requested can be achieved exactly;
      *    the nearest will be chosen and returned"
      */
-    return !spi_init(spi0, MFRC522_CFG_SPI_SPEED_MHZ);
+    return !spi_init(MFRC522_CFG_SPI_INSTANCE, MFRC522_CFG_SPI_SPEED_MHZ);
 }
 
 /**
@@ -183,6 +211,7 @@ uint8_t mfrc522_interface_spi_init(void)
  */
 uint8_t mfrc522_interface_spi_deinit(void)
 {
+    mfrc522_interface_debug_print("WARN: %s not implemented!\n", __FUNCTION__);
     return 0;
 }
 
@@ -198,7 +227,10 @@ uint8_t mfrc522_interface_spi_deinit(void)
  */
 uint8_t mfrc522_interface_spi_read(uint8_t reg, uint8_t *buf, uint16_t len)
 {
-    return 0;
+    cs_select();
+    uint16_t n_bytes_read = spi_read_blocking(MFRC522_CFG_SPI_INSTANCE, reg, buf, len);
+    cs_deselect();
+    return (uint8_t) (n_bytes_read == len) ? 0 : 1;
 }
 
 /**
@@ -213,7 +245,10 @@ uint8_t mfrc522_interface_spi_read(uint8_t reg, uint8_t *buf, uint16_t len)
  */
 uint8_t mfrc522_interface_spi_write(uint8_t reg, uint8_t *buf, uint16_t len)
 {
-    return 0;
+    cs_select();
+    uint16_t n_bytes_written = spi_write_blocking(MFRC522_CFG_SPI_INSTANCE, buf, len);
+    cs_deselect();
+    return (uint8_t) (n_bytes_written == len) ? 0 : 1;
 }
 
 /**