Add the ability to do SPI reads (#12)

* Add the ability to do SPI reads

* lint

Co-authored-by: Mark Harfouche <mark.harfouche@gmail.com>

CHANGELOG.md

@@ -1,3 +1,7 @@
+### 0.0.17
+
+* Add the ability to do SPI byte reads
+
 ### 0.0.16
 
 * Bugfix: Ensure that analog reads return unsigned values.

src/commandconstants.hpp

@@ -43,6 +43,7 @@ int spi_settings(CommandRouter *cmd, int argc, const char **argv);
 int spi_begin_transaction(CommandRouter *cmd, int argc, const char **argv);
 int spi_end_transaction(CommandRouter *cmd, int argc, const char **argv);
 int spi_transfer(CommandRouter *cmd, int argc, const char **argv);
+int spi_read_byte(CommandRouter *cmd, int argc, const char **argv);
 int spi_transfer_bulk(CommandRouter *cmd, int argc, const char **argv);
 int spi_set_clock_divider(CommandRouter *cmd, int argc, const char **argv);
 // Syntax is: {short command, description, syntax}
@@ -116,6 +117,8 @@ command_item_t command_list[] = {
      spi_end_transaction},
     {"spi_transfer", "SPI Transfer 8bits of data", "spi_transfer data",
      spi_transfer},
+    {"spi_read_byte", "SPI transfer register address and read a byte",
+     "spi_read_byte data", spi_read_byte},
     {"spi_transfer_bulk", "SPI transfer multiple sets of 8 bits of data",
      "spi_transfer_bulk data[0] data[1] data[2] [...]", spi_transfer_bulk},
     {nullptr, nullptr, nullptr, nullptr}};

src/main.cpp

@@ -473,6 +473,19 @@ int spi_transfer(CommandRouter *cmd, int argc, const char **argv) {
   return 0;
 }
 
+int spi_read_byte(CommandRouter *cmd, int argc, const char **argv) {
+  if (argc != 2) {
+    return EINVAL;
+  }
+  uint8_t data = strtol(argv[1], nullptr, 0);
+  SPI.beginTransaction(my_spi_settings());
+  SPI.transfer(data);
+  uint8_t received_byte = SPI.transfer(0xff);
+  SPI.endTransaction();
+  snprintf(cmd->buffer, cmd->buffer_size, "0x%02X", received_byte);
+  return 0;
+}
+
 int spi_transfer_bulk(CommandRouter *cmd, int argc, const char **argv) {
   uint8_t data;
   if (argc == 1) {